Coherent 10-Q 6 Feb 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Dec. 29, 2018	Feb. 04, 2019
DEI [Abstract]
Entity Registrant Name	COHERENT INC
Trading Symbol	COHR
Entity Central Index Key	21,510
Document Type	10-Q
Document Period End Date	Dec. 29, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,019
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--09-28
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		24,326,589
Entity Emerging Growth Company	false
Entity Small Business	false

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Income Statement [Abstract]
Net sales	$ 383,146	$ 477,565
Cost of sales	233,796	260,542
Gross profit	149,350	217,023
Operating expenses:
Research and development	28,942	31,392
Selling, general and administrative	64,557	73,437
Impairment and other charges	0	265
Amortization of intangible assets	3,040	2,606
Total operating expenses	96,539	107,700
Income from operations	52,811	109,323
Other income (expense):
Interest income	228	471
Interest expense	(4,901)	(8,747)
Other—net	(4,478)	(224)
Total other income (expense), net	(9,151)	(8,500)
Income from continuing operations before income taxes	43,660	100,823
Provision for income taxes	8,110	58,920
Net income from continuing operations	35,550	41,903
Loss from discontinued operations, net of income taxes	0	(2)
Net income	$ 35,550	$ 41,901
Net income per share:
Basic (in USD per share)	$ 1.46	$ 1.70
Diluted (in USD per share)	$ 1.45	$ 1.67
Shares used in computation:
Basic (shares)	24,268	24,635
Diluted (shares)	24,472	25,025

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands		3 Months Ended
		Dec. 29, 2018	Dec. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income		$ 35,550	$ 41,901
Other comprehensive income (loss):
Translation adjustment, net of taxes	[1],[2]	(5,690)	92
Changes in unrealized losses on available-for-sale securities, net of taxes	[1],[3]	0	(7)
Defined benefit pension plans, net of taxes	[1],[4]	8	147
Other comprehensive income (loss), net of tax	[1]	(5,682)	232
Comprehensive income		29,868	42,133
Available-for-sale securities, tax expense (benefits)		0	4
Defined benefit plans, tax benefits		$ (6)	$ (46)
[1]	Reclassification adjustments were not significant during the three months ended December 29, 2018 and December 30, 2017.
[2]	Tax benefits of $2,755 and $0 were provided on translation adjustments during the three months ended December 29, 2018 and December 30, 2017, respectively.
[3]	Tax benefits of $0 and $4 were provided on changes in unrealized gains (losses) on available-for-sale securities for the three months ended December 29, 2018 and December 30, 2017, respectively.
[4]	Tax benefits of $6 and $46 were provided on changes in defined benefit pension plans for the three months ended December 29, 2018 and December 30, 2017, respectively.

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity Condensed Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total		Common Stock	Add. Paid-in Capital	Accum. Other Comp. Income (Loss)	Retained Earnings
Beginning balance at Sep. 30, 2017	$ 1,163,264		$ 245	$ 171,403	$ 19,906	$ 971,710
Shares, beginning balance (in shares) at Sep. 30, 2017			24,631
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under stock plans, net of shares withheld for employee taxes	(30,747)		$ 2	(30,749)
Common stock issued under stock plans, net of shares withheld for employee taxes (in shares)			191
Cumulative effect of change in accounting principle	13,621					13,621
Stock-based compensation	7,110			7,110
Net income	41,901					41,901
Other comprehensive income (loss), net of tax	232	[1]			232	0
Ending balance at Dec. 30, 2017	1,195,381		$ 247	147,764	20,138	1,027,232
Shares, ending balance (in shares) at Dec. 30, 2017			24,822
Beginning balance at Sep. 29, 2018	$ 1,314,464		$ 242	78,700	2,833	1,232,689
Shares, beginning balance (in shares) at Sep. 29, 2018	24,299		24,299
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under stock plans, net of shares withheld for employee taxes	$ (9,139)		$ 2	(9,141)
Common stock issued under stock plans, net of shares withheld for employee taxes (in shares)			223
Repurchase of common stock	(25,501)		$ (2)	(25,499)
Repurchase of common stock (in shares)			(195)
Stock-based compensation	7,791			7,791
Net income	35,550					35,550
Other comprehensive income (loss), net of tax	(5,682)	[1]			(5,682)	0
Ending balance at Dec. 29, 2018	$ 1,317,483		$ 242	$ 51,851	$ (2,849)	$ 1,268,239
Shares, ending balance (in shares) at Dec. 29, 2018	24,327		24,327
[1]	Reclassification adjustments were not significant during the three months ended December 29, 2018 and December 30, 2017.

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 29, 2018	Sep. 29, 2018
Current assets:
Cash and cash equivalents	$ 314,997	$ 310,495
Restricted cash	827	858
Short-term investments	5,019	120
Accounts receivable—net of allowances of $5,018 and $4,568, respectively	330,892	355,208
Inventories	493,156	486,741
Prepaid expenses and other assets	84,141	85,080
Total current assets	1,229,032	1,238,502
Property and equipment, net	320,933	311,793
Goodwill	442,236	442,940
Intangible assets, net	135,941	142,293
Non-current restricted cash	12,514	12,692
Other assets	112,956	111,749
Total assets	2,253,612	2,259,969
Current liabilities:
Short-term borrowings and current-portion of long-term obligations	46,670	5,072
Accounts payable	74,738	70,292
Income taxes payable	94,302	114,145
Other current liabilities	161,401	183,329
Total current liabilities	377,111	372,838
Long-term obligations	413,505	420,711
Other long-term liabilities	145,513	151,956
Commitments and contingencies (Note 12)
Stockholders' equity:
Common stock, value	242	242
Additional paid-in capital	51,851	78,700
Accumulated other comprehensive income (loss)	(2,849)	2,833
Retained earnings	1,268,239	1,232,689
Total stockholders’ equity	1,317,483	1,314,464
Total liabilities and stockholders’ equity	$ 2,253,612	$ 2,259,969

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 29, 2018	Sep. 29, 2018
Condensed Consolidated Balance Sheets (Parenthetical) [Abstract]
Allowance for Doubtful Accounts Receivable	$ 5,018	$ 4,568
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	500,000,000	500,000,000
Common Stock, Shares, Outstanding	24,327,000	24,299,000

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Cash flows from operating activities:
Net income	$ 35,550	$ 41,901
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	13,916	12,555
Amortization of intangible assets	15,067	15,100
Deferred income taxes	(1,505)	13,121
Amortization of debt issuance cost	1,288	3,815
Stock-based compensation	7,876	7,076
Non-cash restructuring charges	76	430
Other non-cash expense	1	377
Changes in assets and liabilities, net of effect of acquisitions:
Accounts receivable	23,635	(1,219)
Inventories	(9,501)	(16,128)
Prepaid expenses and other assets	1,199	(6,364)
Other long-term assets	2,332	(3,365)
Accounts payable	4,736	4,676
Income taxes payable/receivable	(21,842)	29,751
Other current liabilities	(20,685)	(39,336)
Other long-term liabilities	(832)	2,588
Cash flows from discontinued operations	0	2
Net cash provided by operating activities	51,311	64,980
Cash flows from investing activities:
Purchases of property and equipment	(23,137)	(23,683)
Proceeds from dispositions of property and equipment	0	26
Purchases of available-for-sale securities	(5,000)	(14,894)
Proceeds from sales and maturities of available-for-sale securities	121	9,711
Acquisition of businesses, net of cash acquired	(18,881)	0
Investment at cost	3,423	0
Proceeds from sale of discontinued operation	0	25,000
Net cash used in investing activities	(50,320)	(3,840)
Cash flows from financing activities:
Short-term borrowings	68,124	2,354
Repayments of short-term borrowings	(26,476)	(622)
Repayments of long-term borrowings	(1,907)	(90,363)
Issuance of common stock under employee stock option and purchase plans	5,704	4,899
Net settlement of restricted common stock	(14,843)	(35,646)
Repurchase of common stock	(25,501)	0
Net cash provided by (used in) financing activities	5,101	(119,378)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(1,799)	943
Net increase (decrease) in cash, cash equivalents and restricted cash	4,293	(57,295)
Cash, cash equivalents and restricted cash, beginning of period	324,045	457,087
Cash, cash equivalents and restricted cash, end of period	328,338	399,792
Non-cash investing and financing activities:
Unpaid property and equipment purchases	$ 6,082	$ 3,853

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows - Reconciliation - USD ($) $ in Thousands	Dec. 29, 2018	Sep. 29, 2018	Dec. 30, 2017	Sep. 30, 2017
Statement of Cash Flows [Abstract]
Cash and cash equivalents	$ 314,997	$ 310,495	$ 385,735
Restricted cash	827	858	1,100
Non-current restricted cash	12,514	12,692	12,957
Total cash, cash equivalents, and restricted cash shown in the condensed consolidated statement of cash flows	$ 328,338	$ 324,045	$ 399,792	$ 457,087

Basis of Presentation

Basis of Presentation	3 Months Ended
	Dec. 29, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	BASIS OF PRESENTATION The accompanying unaudited condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission ("SEC"). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") have been condensed or omitted pursuant to such rules and regulations. These interim condensed consolidated financial statements and notes thereto should be read in conjunction with the consolidated financial statements and notes thereto filed by Coherent, Inc. on Form 10-K for the fiscal year ended September 29, 2018 . In the opinion of management, all adjustments necessary for a fair presentation of financial condition and results of operation as of and for the periods presented have been made and include only normal recurring adjustments. Interim results of operations are not necessarily indicative of results to be expected for the year or any other interim periods. Our fiscal year ends on the Saturday closest to September 30 and our first fiscal quarters include 13 weeks of operations in each fiscal year presented. Fiscal year 2019 and 2018 both include 52 weeks. The consolidated financial statements include the accounts of Coherent, Inc. and its direct and indirect subsidiaries (collectively, the "Company", "we", "our", "us" or "Coherent"). Intercompany balances and transactions have been eliminated. On October 5, 2018, we acquired privately held Ondax, Inc. ("Ondax"). On March 8, 2018, we acquired privately held O.R. Lasertechnologie GmbH and certain assets of its U.S.-based affiliate (collectively "OR Laser"). The significant accounting policies of Ondax and OR Laser have been aligned to conform to those of Coherent, and the consolidated financial statements include the results of Ondax and OR Laser as of their acquisition dates. The preparation of consolidated financial statements in conformity with Generally Accepted Accounting Principles ("GAAP") requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Change in Significant Accounting Policies - Revenue Recognition Except for the adoption of Accounting Standard Update ("ASU") 2014-09, Revenue from Contracts with Customers ("ASC 606") on September 30, 2018, there have been no significant changes to our significant accounting policies as of and for the three months ended December 29, 2018, as compared to the significant accounting policies described in our Annual Report on Form 10-K for the year ended September 29, 2018. Effective September 30, 2018, we adopted ASC 606, using the modified retrospective transition method applied to contracts that were not completed as of September 30, 2018. Revenue for the reporting periods after September 30, 2018 are presented under ASC 606, while prior period amounts are reported in accordance with our historical accounting under ASC 605. There was no impact on the opening accumulated retained earnings, revenues, costs, deferred income, customer deposits or other balances as of September 30, 2018 or the quarter ended December 29, 2018 due to the adoption of ASC 606. Under ASC 606, we determine revenue recognition by applying the following five-step approach: Step 1 Identification of the contract, or contracts, with a customer; Step 2 Identification of the performance obligations in the contract; Step 3 Determination of the transaction price; Step 4 Allocation of the transaction price to the performance obligations in the contract; and Step 5 Recognition of revenue when, or as, we satisfy each performance obligation. Contracts and customer purchase orders, which in some cases are governed by master sales agreements, are generally used to determine the existence of an arrangement. In addition, shipping documents and customer acceptance, if applicable, are used to verify delivery and transfer of control. Performance obligations are identified based on the products or services that will be transferred to the customer that are considered distinct. Being distinct is defined as products or services that the customer can benefit from either on its own or together with other resources that are readily available from third parties or from us, and by the product or service being separately identifiable from other promises in the contract. We assess our ability to collect from our customers based primarily on the creditworthiness and past payment history of each customer. Revenue from all sales are recognized at the transaction price. The transaction price is determined based on the consideration to which we will be entitled in exchange for transferring goods or services to the customer adjusted for estimated variable consideration, if any. The consideration associated with customer contracts is generally fixed. Variable consideration includes discounts, rebates, credits and incentives, or other similar items. The amount of consideration that can vary is not a substantial portion of the total consideration. Variable consideration estimates are re-assessed at each reporting period until a final outcome is determined. Changes to the original transaction price due to a change in estimated variable consideration are calculated on a retrospective basis, with the adjustment recorded in the period in which the change occurs. Sales to customers are generally not subject to any price protection or return rights. Accordingly, upon application of steps one through five above, product revenue is recognized upon shipment and transfer of control. The majority of products and services offered by us have readily observable selling prices. As a part of our stand-alone selling price policy, we review product pricing on a periodic basis to identify any significant changes and revise our expected selling price assumptions as appropriate. We record taxes collected on revenue-producing activities on a net basis. Revenue recognition at a point of time Revenues recognized at a point in time consist primarily of product, installation and training. The majority of our sales are made to original equipment manufacturers ("OEMs"), distributors, representatives and end-users. Sales made to customers generally do not require installation of the products by us and are not subject to other post-delivery obligations. Sales to end-users in the scientific market typically require installation by us and, thus, involve post-delivery obligations; however, our post-delivery installation obligations are not essential to the functionality of our products and represent a separate performance obligation. We recognize revenue for these sales following the transfer of control of such products to the customer, which typically occurs upon shipment or delivery depending on the terms of the underlying contracts. In those instances that we have agreed to perform installation or provide training, we defer revenue related to installation or training until these services have been rendered. Our sales to distributors, representatives and end-user customers typically do not have customer acceptance provisions and only certain of our sales to OEM customers and integrators have customer acceptance provisions. Customer acceptance is generally limited to performance under our published product specifications. For the few product sales that have customer acceptance provisions because of more advanced performance than our published specifications, the revenue is recognized when the control transfers or the revenue is deferred until customer acceptance occurs. Revenue recognition over time We periodically enter into contracts in which a customer may purchase a combination of goods and/or services, such as products with maintenance contracts or extended warranty. These contracts are evaluated to determine if the multiple promises are separate performance obligations. Once we determine the performance obligations, we then determine the transaction price, which includes estimating the amount of variable consideration, if any. We then allocate the transaction price to each performance obligation in the contract based on a relative stand-alone selling price charged separately to customers. Extended warranties are sold separately from products and represent a distinct performance obligation. Revenue related to the performance obligation for extended warranties is recognized over time as the customer simultaneously receives and consumes the benefits provided by us. Customized products, for which we have an enforceable right to payment for performance completed to date, are recorded over time. We use the output method to recognize revenue over time for such contracts as it best depicts the satisfaction of our performance obligations. Shipping and handling costs We record costs related to shipping and handling of net sales in cost of sales for all periods presented. Shipping and handling fees billed to customers are included in net sales. Customs duties billed to customers are recorded in cost of sales. Warranty We provide warranties on the majority of our product sales and reserves for estimated warranty costs are recorded during the period of sale. These standard warranties are assurance type warranties and do not offer any services beyond the assurance that the product will continue working as specified. Therefore, these warranties are not considered separate performance obligations in the arrangement. Instead, the expected cost of the warranty is accrued as an expense. The determination of such reserves requires us to make estimates of product return rates and expected costs to repair or replace the products under warranty. We currently establish warranty reserves based on historical warranty costs for each product line. The weighted average warranty period covered is approximately 15 months. If actual return rates and/or repair and replacement costs differ significantly from our estimates, adjustments to cost of sales may be required in future periods. Costs of obtaining a contract We recognize the incremental direct costs of obtaining a contract from a customer as an expense, which primarily includes sales commissions. Sales commissions are recorded at a point of time when control of the product transfers or over a period of time when sales commission provided is expected to be recovered through future services. The costs are recorded within selling, general and administrative expense. Costs incurred prior to the transfer of control of the product to the customer and costs to be amortized over a future period are classified as a prepaid asset and are included in prepaid expenses and other assets. Upon adoption of ASC 606, we determined there was an immaterial impact on sales commissions, therefore, we did not record a transition adjustment on adoption. Payment terms Our standard payment terms are 30 days but vary by the industry and location of the customer and the products or services offered. The time between invoicing and when payment is due is not significant. As our standard payment terms are less than one year, we have elected the practical expedient under ASC 606-10-32-18 and therefore are not required to assess whether each contract has a significant financing component. Customer deposits and deferred revenue When we receive consideration from a customer prior to transferring goods or services under the terms of a sales contract, we record customer deposits or deferred revenue, depending on whether or not the product has shipped to the customer, which are included in other current liabilities or other long-term liabilities when the payment is made or due, whichever is earlier. We recognize deferred revenue as net sales after control of the goods or services has been transferred to the customer and all revenue recognition criteria are met.

Recent Accounting Standards

Recent Accounting Standards	3 Months Ended
	Dec. 29, 2018
Accounting Policies [Abstract]
Recent Accounting Standards	RECENT ACCOUNTING STANDARDS Adoption of New Accounting Pronouncement In May 2014, the Financial Accounting Standards Board ("the FASB") issued ASC 606, which outlines a single, comprehensive model for entities to use in accounting for revenue arising from contracts with customers. The core principle of ASC 606 is to recognize revenue when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. ASC 606 defines a five-step process to achieve this core principle and, accordingly, we expect more judgment and estimates may be required within the revenue recognition process than were required under the previous revenue recognition standard, including identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. ASC 606 permits two methods of adoption: retrospectively to each prior reporting period presented (the full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). We adopted ASC 606 and all related amendments as of September 30, 2018 using the modified retrospective transition method applied to contracts that were not completed as of September 29, 2018 and all new contracts entered into by us subsequent to September 29, 2018. All prior period financial statements and disclosures are presented in accordance with ASC 605. We concluded that the adoption of the new standard did not have a material impact on the timing or amount of revenue recognized as the majority of our sales are not bundled. Therefore, revenue will be recorded at the point-in-time when control transfers, which is consistent with the timing of revenue recognition under ASC 605. See Note 1, "Basis of Presentation" and Note 3, "Revenue Recognition" to the Notes to Condensed Consolidated Financial Statements for more information. There was no impact on the opening accumulated retained earnings, revenues, costs, deferred income, customer deposits or other balances as of September 30, 2018 or the quarter ended December 29, 2018 due to the adoption of ASC 606. In August 2018, the Securities and Exchange Commission ("SEC") adopted amendments to certain disclosure requirements in Securities Act Release No. 33-10532, Disclosure Update and Simplification. The amendments became effective on November 5, 2018. The SEC staff subsequently indicated that it would not object if a filer’s first presentation of changes in shareholders’ equity is included in its Form 10-Q for the quarter that begins after the final rule’s effective date. Among the amendments is the requirement to present the changes in shareholders’ equity in the interim financial statements (either in a separate statement or footnote) in quarterly reports on Form 10-Q. The analysis should present a reconciliation of the beginning balance to the ending balance of each period for which a consolidated statement of operations is required to be filed. We adopted this amendment and have included the first presentation of changes in stockholders’ equity in this quarterly report on Form 10-Q for our first quarter of fiscal 2019. Recently Issued Accounting Pronouncements In February 2016, the FASB issued accounting guidance that modifies lease accounting for lessees to increase transparency and comparability by recording lease assets and liabilities for operating leases and disclosing key information about leasing arrangements. The new standard will become effective for our fiscal year 2020, which begins on September 29, 2019. We will adopt the new guidance utilizing the modified retrospective transition method. We have reviewed the requirements of this standard and have formulated a plan for implementation. We continue to implement internal controls and key system functionality to enable the preparation of financial information. We expect the standard will have a material impact on our consolidated balance sheets, but will not have a material impact on our consolidated income statements. The most significant impact will be the recognition of Right-Of-Use assets and lease liabilities for operating leases, while our accounting for capital leases will remain substantially unchanged. We will continue to assess and disclose the impact that this new guidance will have on our consolidated financial statements, disclosures and related controls, when known.

Revenue Recogition (Notes)

Revenue Recogition (Notes)	3 Months Ended
	Dec. 29, 2018
Revenue from Contract with Customer [Abstract]
Revenue Recognition	REVENUE RECOGNITION Disaggregation of Revenue Based on the information that our chief operating decision maker uses to manage the business, we disaggregate revenue by type and market application within each segment. No other level of disaggregation is required considering the type of products, customers, markets, contracts, duration of contracts, timing of transfer of control and sales channels. The following tables summarize revenue from contracts with customers (in thousands): Sales by revenue type and segment Three months ended December 29, 2018 December 30, 2017 OEM Laser Sources Industrial Lasers & Systems OEM Laser Sources Industrial Lasers & Systems Net sales: Products (1) $ 152,742 $ 111,975 $ 230,768 $ 118,260 Other product and service revenues (2) 89,606 28,823 94,889 33,648 Total net sales $ 242,348 $ 140,798 $ 325,657 $ 151,908 (1) Net sales primarily recognized at a point in time. (2) Includes sales of spare parts, related accessories and other consumable parts as well as revenues from service agreements, of which $12.6 million for the three months ended December 29, 2018 was recognized over time. Sales by market application and segment Three months ended December 29, 2018 December 30, 2017 OEM Laser Sources Industrial Lasers & Systems OEM Laser Sources Industrial Lasers & Systems Net sales: Microelectronics $ 162,203 $ 16,206 $ 250,237 $ 17,939 Materials processing 8,802 95,841 10,453 117,008 OEM components and instrumentation 39,219 27,134 32,997 15,859 Scientific and government programs 32,124 1,617 31,970 1,102 Total net sales $ 242,348 $ 140,798 $ 325,657 $ 151,908 See Note 18 , "Segment and Geographic Information" for revenue disaggregation by reportable segment and geographic region. Contract Balances We record accounts receivable when we have an unconditional right to the consideration. Contract liabilities are recorded when cash payments are received or due in advance of performance. Contract liabilities consist of customer deposits and deferred revenue, where we have unsatisfied or partly satisfied performance obligations. Contract liabilities classified as customer deposits are included in other current liabilities and contract liabilities classified as deferred revenue are included in other current liabilities or other long-term liabilities on our condensed consolidated balance sheets. Payment terms vary by customer. A rollforward of our customer deposits and deferred revenue is as follows (in thousands): Beginning balance, September 30, 2018 (1) $ 55,637 Amount of customer deposits and deferred revenue recognized in income (50,916 ) Additions to customer deposits and deferred revenue 41,270 Translation adjustments (339 ) Ending balance, December 29, 2018 (2) $ 45,652 (1) Beginning customer deposits and deferred revenue as of September 30, 2018 includes $50,546 of current portion and $5,091 of long-term portion. (2) Ending customer deposits and deferred revenue as of December 29, 2018 includes $40,143 of current portion and $5,509 of long-term portion. Remaining performance obligations represent the transaction price allocated to performance obligations that are unsatisfied or partially unsatisfied as of the end of the reporting period. The following table includes estimated revenue expected to be recognized in the future related to performance obligations for sales of maintenance agreements, extended warranties, installation, and contracts with customer acceptance provisions included in customer deposits and deferred revenue as of December 29, 2018 (in thousands): Remainder of fiscal 2019 Fiscal 2020 Fiscal 2021 and after Total Performance Obligations $ 37,626 $ 5,177 $ 2,849 $ 45,652

Business Combinations

Business Combinations	3 Months Ended
	Dec. 29, 2018
Business Combinations [Abstract]
Business Combinations	BUSINESS COMBINATIONS Fiscal 2019 Acquisitions Ondax On October 5, 2018, we acquired privately held Ondax, Inc. ("Ondax") for approximately $12.0 million , excluding transaction costs. Ondax develops and produces photonic components which are used on an OEM basis by the laser industry as well as incorporated into its own stabilized lasers and Raman Spectroscopy systems. Ondax’s operating results have been included in our Industrial Lasers & Systems segment. See Note 18, "Segment and Geographic Information." Our preliminary allocation of the purchase price is as follows (in thousands): Tangible assets: Cash $ 103 Accounts receivable 534 Inventories 1,793 Prepaid expenses and other assets 17 Deferred tax assets 458 Property and equipment 122 Liabilities assumed (499 ) Intangible assets: Existing technology 5,600 Customer relationships 300 Goodwill 3,556 Total $ 11,984 Results of operations for the business have been included in our condensed consolidated financial statements subsequent to the date of acquisition and pro forma results of operations in accordance with authoritative guidance for prior periods have not been presented because the effect of the acquisition was not material to our prior period consolidated financial results. The identifiable intangible assets are being amortized over their respective preliminary useful lives of 1 to 8 years . The fair values of the acquired intangibles were determined using the income approach. In performing these valuations, the key underlying probability-adjusted assumptions of the discounted cash flows were projected revenues, gross margin expectations and operating cost estimates. The valuations were based on the information that was available as of the acquisition date and the expectations and assumptions that have been deemed reasonable by our management. There are inherent uncertainties and management judgment required in these determinations. This acquisition resulted in a purchase price that exceeded the estimated fair value of tangible and intangible assets, which was allocated to goodwill. We believe the amount of goodwill relative to identifiable intangible assets relates to several factors including: (1) potential buyer-specific synergies related to the development of new technologies; and (2) the potential to leverage our sales force to attract new customers. None of the goodwill from this purchase is deductible for tax purposes. Quantum On October 5, 2018, we acquired certain assets of Quantum Coating, Inc. ("Quantum") for approximately $7.0 million , excluding transaction costs, and will account for the transaction as an asset purchase. Our preliminary allocation of the purchase price is as follows (in thousands): Tangible assets: Property and equipment $ 2,770 Intangible assets: Existing technology 1,600 Customer relationships 230 Production know-how 2,300 Backlog 100 Total $ 7,000 The identifiable intangible assets are being amortized over their respective preliminary useful lives of 1 to 5 years . The fair values of the acquired intangibles were determined using the income approach. In performing these valuations, the key underlying probability-adjusted assumptions of the discounted cash flows were projected revenues, gross margin expectations and operating cost estimates. The valuations were based on the information that was available as of the acquisition date and the expectations and assumptions that have been deemed reasonable by our management. There are inherent uncertainties and management judgment required in these determinations. Fiscal 2018 Acquisitions OR Laser On March 8, 2018, we acquired OR Laser for approximately $47.4 million , excluding transaction costs. OR Laser produced laser-based material processing equipment for a variety of uses, including additive manufacturing, welding, cladding, marking, engraving and drilling. OR Laser’s operating results have been included in our Industrial Lasers & Systems segment. See Note 18, "Segment and Geographic Information." Our allocation of the purchase price is as follows (in thousands): Tangible assets: Cash $ 1,936 Accounts receivable 3,973 Inventories 2,360 Prepaid expenses and other assets 630 Property and equipment 1,515 Liabilities assumed (5,119 ) Deferred tax liabilities (4,517 ) Intangible assets: Existing technology 14,100 Non-competition 200 Backlog 100 Customer relationships 700 Trademarks 50 Goodwill 31,456 Total $ 47,384 Results of operations for the business have been included in our condensed consolidated financial statements subsequent to the date of acquisition and pro forma results of operations in accordance with authoritative guidance for prior periods have not been presented because the effect of the acquisition was not material to our prior period consolidated financial results. The identifiable intangible assets are being amortized over their respective preliminary useful lives of 1 to 8 years. The fair values of the acquired intangibles were determined using the income approach. In performing these valuations, the key underlying probability-adjusted assumptions of the discounted cash flows were projected revenues, gross margin expectations and operating cost estimates. The valuations were based on the information that was available as of the acquisition date and the expectations and assumptions that have been deemed reasonable by our management. There are inherent uncertainties and management judgment required in these determinations. This acquisition resulted in a purchase price that exceeded the estimated fair value of tangible and intangible assets, which was allocated to goodwill. We believe the amount of goodwill relative to identifiable intangible assets relates to several factors including: (1) potential buyer-specific synergies related to the development of new technologies related primarily to the additive manufacturing business; and (2) the potential to leverage our sales force to attract new customers and revenue and cross-sell to existing customers. None of the goodwill from this purchase is deductible for tax purposes.

Fair Values

Fair Values	3 Months Ended
	Dec. 29, 2018
Fair Value Disclosures [Abstract]
Fair Values	FAIR VALUES We have not changed our valuation techniques in measuring the fair value of any financial assets and liabilities during the period. We recognize transfers between levels within the fair value hierarchy, if any, at the end of each quarter. There were no transfers between levels during the periods presented. As of December 29, 2018 , we had one investment carried on a cost basis. See Note 9, "Balance Sheet Details". If we were to fair value this investment, it would be based upon Level 3 inputs; this investment is not considered material to our condensed consolidated financial statements. As of September 29, 2018 , we did not have any assets or liabilities valued based upon Level 3 inputs. We measure the fair value of outstanding debt obligations for disclosure purposes on a recurring basis. As of December 29, 2018 , the current and long-term portion of long-term obligations of $5.7 million and $413.5 million , respectively, are reported at amortized cost. As of September 29, 2018 , the current and long-term portion of long-term obligations of $5.1 million and $420.7 million , respectively, are reported at amortized cost. These outstanding obligations are classified as Level 2 as they are not actively traded and are valued using a discounted cash flow model that uses observable market inputs. Based on the discounted cash flow model, the fair value of the outstanding debt approximates amortized cost. Financial assets and liabilities measured at fair value as of December 29, 2018 and September 29, 2018 are summarized below (in thousands): Aggregate Fair Value Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Aggregate Fair Value Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs December 29, 2018 September 29, 2018 (Level 1) (Level 2) (Level 1) (Level 2) Assets: Cash equivalents: Money market fund deposits $ 42,679 $ 42,679 $ — $ 56,285 $ 56,285 $ — U.S. Treasury and agency obligations (1) 121 — 121 — — — Commercial paper (1) 1,197 — 1,197 — — — Short-term investments: U.S. Treasury and agency obligations (1) 5,019 — 5,019 120 — 120 Prepaid and other assets: Foreign currency contracts (2) 789 — 789 1,007 — 1,007 Money market fund deposits — Deferred comp and supplemental plan (3) 808 808 — 522 522 — Mutual funds — Deferred comp and supplemental plan (3) 20,467 20,467 — 21,862 21,862 — Total $ 71,080 $ 63,954 $ 7,126 $ 79,796 $ 78,669 $ 1,127 Liabilities: Other current liabilities: Foreign currency contracts (2) (1,361 ) — (1,361 ) (1,879 ) — (1,879 ) Total $ 69,719 $ 63,954 $ 5,765 $ 77,917 $ 78,669 $ (752 ) ___________________________________________________ (1) Valuations are based upon quoted market prices in active markets involving similar assets. The market inputs used to value these instruments generally consist of market yields, reported trades, broker/dealer quotes or alternative pricing sources with reasonable levels of price transparency. Pricing sources include industry standard data providers, security master files from large financial institutions, and other third party sources which are input into a distribution-curve-based algorithm to determine a daily market value. This creates a "consensus price" or a weighted average price for each security. (2) The principal market in which we execute our foreign currency contracts is the institutional market in an over-the-counter environment with a relatively high level of price transparency. The market participants usually are large commercial banks. Our foreign currency contracts’ valuation inputs are based on quoted prices and quoted pricing intervals from public data sources and do not involve management judgment. See Note 7, "Derivative Instruments and Hedging Activities." (3) The fair value of mutual funds is determined based on quoted market prices. Securities traded on a national exchange are stated at the last reported sales price on the day of valuation; other securities traded in over-the-counter markets and listed securities for which no sale was reported on that date are stated as the last quoted bid price.

Short-Term Investments

Short-Term Investments	3 Months Ended
	Dec. 29, 2018
Cash, Cash Equivalents, and Short-term Investments [Abstract]
Short-Term Investments	SHORT-TERM INVESTMENTS We consider all highly liquid investments with maturities of three months or less at the time of purchase to be cash equivalents. Investments classified as available-for-sale are reported at fair value with unrealized gains and losses, net of related income taxes, recorded as a separate component of other comprehensive income ("OCI") in stockholders’ equity until realized. Interest and amortization of premiums and discounts for debt securities are included in interest income. Gains and losses on securities sold are determined based on the specific identification method and are included in other income (expense). Cash, cash equivalents and short-term investments consist of the following (in thousands): December 29, 2018 Cost Basis Unrealized Gains Unrealized Losses Fair Value Cash and cash equivalents $ 314,996 $ 1 $ — $ 314,997 Short-term investments: Available-for-sale securities: U.S. Treasury and agency obligations 5,000 19 — 5,019 Total short-term investments $ 5,000 $ 19 $ — $ 5,019 September 29, 2018 Cost Basis Unrealized Gains Unrealized Losses Fair Value Cash and cash equivalents $ 310,495 $ — $ — $ 310,495 Short-term investments: Available-for-sale securities: U.S. Treasury and agency obligations 120 — — 120 Total short-term investments $ 120 $ — $ — $ 120 There were no unrealized losses at December 29, 2018 . There were no unrealized gains or losses at September 29, 2018 . The amortized cost and estimated fair value of available-for-sale investments in debt securities as of December 29, 2018 and September 29, 2018 classified as short-term investments on our condensed consolidated balance sheet were as follows (in thousands): December 29, 2018 September 29, 2018 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Investments in available-for-sale debt securities due in less than one year $ 5,000 $ 5,019 $ 120 $ 120 During the three months ended December 29, 2018 , we received no proceeds from the sale of available-for-sale securities and realized no gross gains or losses. During the three months ended December 30, 2017 , we received proceeds totaling $2.4 million from the sale of available-for-sale securities and realized no gross gains or losses.

Derivative Instruments and Hedg

Derivative Instruments and Hedging Activities	3 Months Ended
	Dec. 29, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments and Hedging Activities	DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES We maintain operations in various countries outside of the United States and have foreign subsidiaries that manufacture and sell our products in various global markets. The majority of our sales are transacted in U.S. dollars. However, we do generate revenues in other currencies, primarily the Euro, Japanese Yen, South Korean Won and Chinese Renminbi (RMB). As a result, our earnings, cash flows and cash balances are exposed to fluctuations in foreign currency exchange rates. We attempt to limit these exposures through financial market instruments. We utilize derivative instruments, primarily forward contracts with maturities of two months or less, to manage our exposure associated with anticipated cash flows and net asset and liability positions denominated in foreign currencies. Gains and losses on the forward contracts are mitigated by gains and losses on the underlying instruments. We do not use derivative financial instruments for speculative or trading purposes. The credit risk amounts represent the Company’s gross exposure to potential accounting loss on derivative instruments that are outstanding or unsettled if all counterparties failed to perform according to the terms of the contract, based on then-current currency rates at each respective date. Non-Designated Derivatives The outstanding notional contract and fair value asset (liability) amounts of non-designated hedge contracts, with maximum maturity of two months, are as follows (in thousands): U.S. Notional Contract Value U.S. Fair Value December 29, 2018 September 29, 2018 December 29, 2018 September 29, 2018 Euro currency hedge contracts Purchase $ 135,736 $ 126,589 $ 611 $ (1,554 ) Sell $ (7,134 ) $ (8,701 ) $ (31 ) 43 Japanese Yen currency hedge contracts Purchase $ 2,288 $ — $ 36 $ — Sell $ (41,210 ) $ (27,473 ) $ (809 ) $ 637 South Korean Won currency hedge contracts Purchase $ 1,660 $ 2,778 $ (16 ) $ 27 Sell $ (39,665 ) $ (31,920 ) $ (147 ) $ (109 ) Chinese RMB currency hedge contracts Purchase $ 2,191 $ 5,852 $ (16 ) $ (33 ) Sell $ (37,938 ) $ (51,137 ) $ (331 ) $ 300 Singapore Dollar currency hedge contracts Purchase $ 34,687 $ 30,127 $ 69 $ (131 ) Other foreign currency hedge contracts Purchase $ 5,682 $ 4,091 $ 21 $ (13 ) Sell $ (7,387 ) $ (5,934 ) $ 41 $ (39 ) The fair value of our derivative instruments is included in prepaid expenses and other assets and in other current liabilities in our Condensed Consolidated Balance Sheets. See Note 5, "Fair Values." During the three months ended December 29, 2018 and December 30, 2017 , we recognized losses of $3.7 million and $2.6 million , respectively, in other income (expense) for derivative instruments not designated as hedging instruments. Master Netting Arrangements To mitigate credit risk in derivative transactions, we enter into master netting arrangements that allow each counterparty in the arrangements to net settle amounts of multiple and separate derivative transactions under certain conditions. We present the fair value of derivative assets and liabilities within our condensed consolidated balance sheet on a gross basis even when derivative transactions are subject to master netting arrangements and may otherwise qualify for net presentation. The impact of netting derivative assets and liabilities is not material to our financial position for any of the periods presented. Our derivative contracts do not contain any credit risk related contingent features and do not require collateral or other security to be furnished by us or the counterparties.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Dec. 29, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	GOODWILL AND INTANGIBLE ASSETS During the three months ended December 29, 2018 , we noted no indications of impairment or triggering events to cause us to review goodwill for potential impairment. We will conduct our annual goodwill testing during the fourth fiscal quarter. The changes in the carrying amount of goodwill by segment for the period from September 29, 2018 to December 29, 2018 are as follows (in thousands): OEM Laser Sources Industrial Lasers & Systems Total Balance as of September 29, 2018 $ 100,732 $ 342,208 $ 442,940 Additions (see Note 4) — 3,556 3,556 Translation adjustments and other (1,106 ) (3,154 ) (4,260 ) Balance as of December 29, 2018 $ 99,626 $ 342,610 $ 442,236 Components of our amortizable intangible assets are as follows (in thousands): December 29, 2018 September 29, 2018 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Existing technology $ 206,454 $ (104,889 ) $ 101,565 $ 201,759 $ (94,376 ) $ 107,383 Customer relationships 49,238 (23,384 ) 25,854 50,359 (22,383 ) 27,976 Trade name 5,788 (4,233 ) 1,555 5,888 (3,818 ) 2,070 Production know-how 2,300 (114 ) 2,186 — — — In-process research & development 4,781 — 4,781 4,864 — 4,864 Total $ 268,561 $ (132,620 ) $ 135,941 $ 262,870 $ (120,577 ) $ 142,293 For accounting purposes, when an intangible asset is fully amortized, it is removed from the disclosure schedule. Amortization expense for intangible assets for the three months ended December 29, 2018 and December 30, 2017 was $15.1 million and $15.1 million , respectively. The change in the accumulated amortization also includes $2.4 million (decrease) and $0.1 million (increase) of foreign exchange impact for the three months ended December 29, 2018 and December 30, 2017 , respectively. At December 29, 2018 , estimated amortization expense for the remainder of fiscal 2019 , the next five succeeding fiscal years and all fiscal years thereafter are as follows (in thousands): Estimated Amortization Expense 2019 (remainder) $ 42,342 2020 49,637 2021 18,328 2022 7,188 2023 4,491 2024 3,108 Thereafter 6,066 Total (excluding IPR&D) $ 131,160

Balance Sheet Details

Balance Sheet Details	3 Months Ended
	Dec. 29, 2018
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Details	BALANCE SHEET DETAILS Inventories consist of the following (in thousands): December 29, September 29, Purchased parts and assemblies $ 148,940 $ 137,566 Work-in-process 178,947 186,240 Finished goods 165,269 162,935 Total inventories $ 493,156 $ 486,741 Prepaid expenses and other assets consist of the following (in thousands): December 29, September 29, Prepaid and refundable income taxes $ 39,165 $ 37,884 Other taxes receivable 15,267 16,930 Prepaid expenses and other assets 29,709 30,266 Total prepaid expenses and other assets $ 84,141 $ 85,080 Other assets consist of the following (in thousands): December 29, September 29, Assets related to deferred compensation arrangements $ 35,465 $ 37,370 Deferred tax assets 65,043 64,858 Other assets (1) 12,448 9,521 Total other assets $ 112,956 $ 111,749 (1) In the first quarter of fiscal 2019, we invested 3.0 million Euro ( $3.4 million ) in 3D-Micromac AG, a company that specializes in laser micromachining. The investment is included in other assets and is being carried on a cost basis and will be adjusted, as necessary, for impairment. Other current liabilities consist of the following (in thousands): December 29, September 29, Accrued payroll and benefits $ 45,044 $ 55,704 Deferred revenue 21,997 30,613 Warranty reserve 40,489 40,220 Accrued expenses and other 35,725 36,859 Customer deposits 18,146 19,933 Total other current liabilities $ 161,401 $ 183,329 Components of the reserve for warranty costs during the first three months of fiscal 2019 and 2018 were as follows (in thousands): Three Months Ended December 29, December 30, Beginning balance $ 40,220 $ 36,149 Additions related to current period sales 17,081 14,140 Warranty costs incurred in the current period (16,376 ) (12,404 ) Accruals resulting from acquisitions 21 — Adjustments to accruals related to foreign exchange and other (457 ) (76 ) Ending balance $ 40,489 $ 37,809 Other long-term liabilities consist of the following (in thousands): December 29, September 29, Long-term taxes payable $ 35,709 $ 36,336 Deferred compensation 39,021 40,895 Defined benefit plan liabilities 37,873 37,528 Deferred tax liabilities 21,615 26,339 Deferred revenue 5,509 5,091 Asset retirement obligations liability 4,551 4,529 Other long-term liabilities 1,235 1,238 Total other long-term liabilities $ 145,513 $ 151,956

Borrowings

Borrowings	3 Months Ended
	Dec. 29, 2018
Debt Disclosure [Abstract]
Borrowings	BORROWINGS On November 7, 2016 (the "Closing Date"), we entered into a Credit Agreement by and among us, Coherent Holding BV & Co. K.G. (formerly Coherent Holding GmbH), as borrower (the "Borrower"), and certain of our direct and indirect subsidiaries from time to time party thereto, as guarantors, the lenders from time to time party thereto, Barclays Bank PLC, as administrative agent and an L/C Issuer, Bank of America, N.A., as an L/C Issuer, and MUFG Union Bank, N.A., as an L/C Issuer (the "Initial Credit Agreement" and, as amended by the Amendments (defined below), the "Credit Agreement"). The Initial Credit Agreement provided for a 670.0 million Euro senior secured term loan facility (the "Euro Term Loan") and a $100.0 million senior secured revolving credit facility (the "Revolving Credit Facility") with a $30.0 million letter of credit sublimit and a $10.0 million swing line sublimit, in each case, which may be increased from time to time pursuant to an incremental feature set forth in the Credit Agreement. On November 7, 2016, the Borrower borrowed the full 670.0 million Euros under the Euro Term Loan and its proceeds were used to finance the acquisition of Rofin and pay related fees and expenses. On November 7, 2016, we also used 10.0 million Euros of the capacity under the Revolving Credit Facility for the issuance of a letter of credit. On November 20, 2018, we borrowed an additional $40.0 million under the Revolving Credit Facility. The Initial Credit Agreement was amended on May 8, 2017 (the "First Amendment") to reduce the interest rate margins applicable to the Euro Term Loan and was amended again on July 5, 2017 (the "Second Amendment" and, together with the First Amendment, the "Amendments") to make certain technical changes in connection with the conversion of the Borrower from a German company with limited liability to a German limited partnership. The Credit Agreement contains customary mandatory prepayment provisions. The Borrower has the right to prepay loans under the Credit Agreement in whole or in part at any time without premium or penalty, subject to customary breakage costs. Revolving loans may be borrowed, repaid and reborrowed until the fifth anniversary of the Closing Date, at which time all outstanding revolving loans must be repaid. The Euro Term Loan matures on the seventh anniversary of the Closing Date, at which time all outstanding principal and accrued and unpaid interest on the Euro Term Loan must be repaid. As of December 29, 2018 , the outstanding principal amount of the Euro Term Loan was 369.9 million Euros. As of December 29, 2018 , the outstanding amount of the Revolving Credit Facility was $40.0 million plus a 10.0 million Euro letter of credit. Loans under the Credit Agreement bear interest, at the Borrower’s option, at a rate equal to either (i)(x) in the case of calculations with respect to U.S. Dollars or certain other alternative currencies, the London interbank offered rate (the "LIBOR") or (y) in the case of calculations with respect to the Euro, the euro interbank offered rate ("EURIBOR" and, together with LIBOR), the "Eurocurrency Rate") or (ii) a base rate (the "Base Rate") equal to the highest of (x) the federal funds rate, plus 0.50% , (y) the prime rate then in effect and (z) the Eurocurrency Rate for loans denominated in U.S. dollars applicable to a one-month interest period, plus 1.0% , in each case, plus an applicable margin that is subject to adjustment pursuant to a pricing grid based on consolidated total gross leverage ratio. At December 29, 2018 , the applicable margin for Euro Term Loans borrowed as Eurocurrency Rate loans was 2.00% per annum and as Base Rate loans was 1.00% and the applicable margin for revolving loans borrowed as Eurocurrency Rate loans was 3.75% per annum and as Base Rate loans was 2.75% per annum. Interest on Base Rate Loans is payable quarterly in arrears. Interest on Eurocurrency Rate loans is payable at the end of the applicable interest period (or at three month intervals if the interest period exceeds three months). The Credit Agreement requires the Borrower to make scheduled quarterly payments on the Euro Term Loan of 0.25% of the original principal amount of the Euro Term Loan, with any remaining principal payable at maturity. A commitment fee accrues on any unused portion of the revolving loan commitments under the Credit Agreement at a rate of 0.375% or 0.5% depending on the consolidated total gross leverage ratio at any time of determination. The Borrower is also obligated to pay other customary fees for a credit facility of this size and type. On the Closing Date, we and certain of our direct and indirect subsidiaries, as guarantors, provided an unconditional guaranty of all obligations of the Borrower and the other loan parties arising under the Credit Agreement, the other loan documents and under swap contracts and treasury management agreements with the lenders or their affiliates (with certain limited exceptions). The Borrower and the guarantors have also granted security interests in substantially all of their assets to secure such obligations. The Credit Agreement contains customary affirmative and negative covenants, including covenants limiting the ability of us and our subsidiaries to, among other things, incur debt, grant liens, make investments, make certain restricted payments, transact with affiliates, and sell assets. The Credit Agreement also requires us and our subsidiaries to maintain a senior secured net leverage ratio as of the last day of each fiscal quarter of less of than or equal to 3.50 to 1.00. We were in compliance with all covenants at December 29, 2018 . We incurred $28.5 million of debt issuance costs related to the Euro Term Loan and $0.5 million of debt issuance costs to the original lenders related to the First Amendment, which are included in short-term borrowings and current portion of long-term obligations and long-term obligations in the condensed consolidated balance sheets and will be amortized to interest expense over the seven year life of the Euro Term Loan using the effective interest method, adjusted to accelerate amortization related to voluntary repayments. We incurred $2.3 million of debt issuance costs in connection with the Revolving Credit Facility which were capitalized and included in prepaid expenses and other assets and other assets in the condensed consolidated balance sheets and will be amortized to interest expense using the straight-line method over the contractual term of five years of the Revolving Credit Facility. Additional sources of cash available to us were international currency lines of credit and bank credit facilities totaling $26.4 million as of December 29, 2018 , of which $18.0 million was unused and available. These unsecured international credit facilities were used in Europe and Japan during the first three months of fiscal 2019 . As of December 29, 2018 , we had utilized $7.4 million of the international credit facilities as guarantees in Europe and $1.0 million of the international credit facilities as borrowings in Japan. Short-term borrowings and current portion of long-term obligations consist of the following (in thousands): December 29, September 29, Current portion of Euro Term Loan (1) $ 3,065 $ 3,092 1.3% Term loan due 2024 1,783 1,448 1.0% State of Connecticut term loan due 2023 375 374 OR Laser loans 158 158 Capital lease obligations 270 — Line of credit borrowings 41,019 — Total short-term borrowings and current portion of long-term obligations $ 46,670 $ 5,072 (1) Net of debt issuance costs of $4.6 million and $4.7 million at December 29, 2018 and September 29, 2018 , respectively. Long-term obligations consist of the following (in thousands): December 29, September 29, Euro Term Loan due 2024 (1) $ 404,562 $ 411,661 1.3% Term loan due 2024 6,775 7,242 1.0% State of Connecticut term loan due 2023 1,312 1,406 OR Laser loans 364 402 Capital lease obligations 492 — Total long-term obligations $ 413,505 $ 420,711 (1) Net of debt issuance costs of $9.9 million and $11.2 million at December 29, 2018 and September 29, 2018 , respectively. Contractual maturities of our debt obligations as of December 29, 2018 are as follows (in thousands): Amount 2019 (remainder) $ 7,766 2020 9,823 2021 9,808 2022 9,555 2023 9,461 2024 387,199 Total $ 433,612

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Dec. 29, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION Fair Value of Stock Compensation We recognize compensation expense for all share based payment awards based on the fair value of such awards. The expense is recognized on a straight-line basis per tranche over the respective requisite service period of the awards. Determining Fair Value The fair values of shares purchased under the Employee Stock Purchase Plan ("ESPP") for the three months ended December 29, 2018 and December 30, 2017 , respectively, were estimated using the following weighted-average assumptions: Employee Stock Purchase Plan Three Months Ended December 29, December 30, Expected life in years 0.5 0.5 Expected volatility 48.3 % 47.9 % Risk-free interest rate 2.35 % 1.21 % Expected dividend yield — % — % Weighted average fair value per share $ 42.80 $ 70.75 We grant performance restricted stock units to officers and certain employees. The performance restricted stock unit agreements provide for the award of performance stock units with each unit representing the right to receive one share of our common stock to be issued after the applicable award vesting period. The final number of units awarded, if any, for these performance grants will be determined as of the vesting dates, based upon our total shareholder return over the performance period compared to the applicable Russell Index and could range from no units to a maximum of twice the initial award units. The weighted average fair value for these performance units was determined using a Monte Carlo simulation model incorporating the following weighted average assumptions: Three Months Ended December 29, 2018 December 30, 2017 Risk-free interest rate 2.9 % 1.7 % Volatility 43.7 % 37.0 % Weighted average fair value per share $ 117.43 $ 315.05 We recognize the estimated cost of these awards, as determined under the simulation model, over the related service period of approximately 3 years, with no adjustment in future periods based upon the actual shareholder return over the performance period. Stock Compensation Expense The following table shows total stock-based compensation expense and related tax benefits included in the condensed consolidated statements of operations for the three months ended December 29, 2018 and December 30, 2017 (in thousands): Three Months Ended December 29, December 30, Cost of sales $ 1,237 $ 988 Research and development 650 668 Selling, general and administrative 5,989 5,420 Income tax benefit (1,233 ) (1,609 ) $ 6,643 $ 5,467 During the three months ended December 29, 2018 , $1.2 million of stock-based compensation cost was capitalized as part of inventory for all stock plans, $1.2 million was amortized into cost of sales and $1.4 million remained in inventory at December 29, 2018 . During the three months ended December 30, 2017 , $1.0 million of stock-based compensation was capitalized as part of inventory for all stock plans, $1.0 million was amortized into cost of sales and $1.3 million remained in inventory at December 30, 2017 . At December 29, 2018 , the total compensation cost related to unvested stock-based awards granted to employees under our stock plans but not yet recognized was approximately $51.6 million . We do not estimate forfeitures. This cost will be amortized on a straight-line basis over a weighted-average period of approximately 1.6 years. Stock Awards Activity The following table summarizes the activity of our time-based and performance restricted stock units for the first three months of fiscal 2019 (in thousands, except per share amounts): Time Based Restricted Stock Units Performance Restricted Stock Units Number of Shares Weighted Average Grant Date Fair Value Number of Shares Weighted Nonvested stock at September 29, 2018 279 $ 155.24 159 $ 155.76 Granted 149 123.26 105 117.43 Vested (1) (155 ) 125.08 (131 ) 74.48 Forfeited (1 ) 189.16 — — Nonvested stock at December 29, 2018 272 $ 154.70 133 $ 184.26 __________________________________________ (1) Service-based restricted stock units vested during the fiscal year. Performance-based restricted stock units included at 100% of target goal; under the terms of the awards, the recipient may earn between 0% and 200% of the award.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Dec. 29, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Indemnifications In the normal course of business, we enter into agreements that contain a variety of representations and warranties and provide for general indemnification. Exposure under these agreements is unknown because claims may be made against us in the future and we may record charges in the future as a result of these indemnification obligations. As of December 29, 2018, we did not have any material indemnification claims that were probable or reasonably possible. Contingencies We are subject to legal claims and litigation arising in the ordinary course of business, such as product liability, employment or intellectual property claims. Although we do not expect that such legal claims and litigation will ultimately have a material adverse effect on our consolidated financial position, results of operations or cash flows, an adverse result in one or more matters could negatively affect our results in the period in which they occur. The United States and many foreign governments impose tariffs and duties on the import and export of certain products we sell. From time to time our customs compliance, product classifications, duty calculations and payments are reviewed or audited by government agencies.

Stock Repurchases

Stock Repurchases	3 Months Ended
	Dec. 29, 2018
Stock Repurchase [Abstract]
Stock Repurchases	STOCK REPURCHASES On February 6, 2018, our board of directors authorized a stock repurchase program authorizing the Company to repurchase up to $100.0 million of our common stock from time to time through January 31, 2019. During fiscal 2018, we repurchased and retired 574,946 shares of outstanding common stock under this program at an average price of $173.91 per share for a total of $100.0 million . On October 28, 2018, our board of directors authorized a stock repurchase program authorizing the Company to repurchase up to $250.0 million of our common stock through December 31, 2019, with a limit of no more than $75.0 million per quarter. During the first quarter of fiscal 2019, we repurchased and retired 194,801 shares of outstanding common stock under this program at an average price of $130.91 per share for a total of $25.5 million .

Earnings Per Share

Earnings Per Share	3 Months Ended
	Dec. 29, 2018
Earnings Per Share [Abstract]
Earnings Per Share	EARNINGS PER SHARE Basic earnings per share is computed based on the weighted average number of shares outstanding during the period, excluding unvested restricted stock. Diluted earnings per share is computed based on the weighted average number of shares outstanding during the period increased by the effect of dilutive employee stock awards, including stock options, restricted stock awards and stock purchase plan contracts, using the treasury stock method. The following table presents information necessary to calculate basic and diluted earnings per share (in thousands, except per share data): Three Months Ended December 29, December 30, Weighted average shares outstanding—basic 24,268 24,635 Dilutive effect of employee stock awards 204 390 Weighted average shares outstanding—diluted 24,472 25,025 Net income from continuing operations $ 35,550 $ 41,903 Loss from discontinued operations, net of income taxes — (2 ) Net income $ 35,550 $ 41,901 A total of 100,520 and 19,375 potentially dilutive securities have been excluded from the diluted share calculation for the three months ended December 29, 2018 and December 30, 2017 , respectively, as their effect was anti-dilutive.

Other Income (Expense)

Other Income (Expense)	3 Months Ended
	Dec. 29, 2018
Other Income and Expenses [Abstract]
Other Income (Expense)	OTHER INCOME (EXPENSE) Other income (expense) is as follows (in thousands): Three Months Ended December 29, December 30, Foreign exchange loss $ (2,177 ) $ (2,235 ) Gain (loss) on deferred compensation investments, net (2,125 ) 1,855 Other (176 ) 156 Other—net $ (4,478 ) $ (224 )

Income Taxes

Income Taxes	3 Months Ended
	Dec. 29, 2018
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXES Income tax expense includes a provision for federal, state and foreign taxes based on the annual estimated effective tax rate applicable to us and our subsidiaries, adjusted for items which are considered discrete to the period. On December 22, 2017, the Tax Cuts and Jobs Act (the "Tax Act") was enacted. The Tax Act contains significant changes to U.S. tax law, including lowering the U.S. corporate income tax rate to 21.0% and implementing a territorial tax system. The Securities Exchange Commission issued guidance under Staff Accounting Bulletin No. 118 ("SAB 118") directing taxpayers to record the impact of the Tax Act as "provisional" when they do not have all the necessary information to complete the accounting under ASC 740. The guidance allows for a measurement period of up to one year after the enactment date of the Tax Act to finalize the recording of the related tax impact. In accordance with SAB 118, we recorded provisional estimates to our consolidated financial statements in fiscal 2018 based on the Tax Act. During the first quarter of fiscal 2019, we further analyzed the income tax effects of the Tax Act and there were no material changes to the provisional amounts disclosed in our fiscal 2018 financial statements. Although our accounting for the effects of the Tax Act is complete under SAB 118, there may be future adjustments based on changes in interpretations of the Tax Act, any legislative updates or final regulations under the Tax Act, any changes in accounting standards for income taxes or related interpretations or any updates or changes in estimates we have utilized to calculate the transitional impact. The Tax Act also made other significant changes to U.S. federal income tax laws, including a global intangible low-taxed income tax (GILTI) and a base erosion anti-abuse tax (BEAT) which became effective for us beginning on September 30, 2018. There is no material impact of GILTI and BEAT expected. Our effective tax rate on income from continuing operations before income taxes for the three months ended December 29, 2018 was 18.6% . Our effective tax rate for the three months ended December 29, 2018 was lower than the U.S. federal tax rate of 21.0% primarily due to the excess tax benefits from restricted stock unit vesting, the benefit of federal research and development tax credits and our Singapore tax exemption. This amount is partially offset by the impact of income subject to foreign tax rates that are higher than the U.S. tax rates, stock-based compensation not deductible for tax purposes and limitations on the deductibility of compensation under IRC Section 162(m). Our effective tax rate on income from continuing operations before income taxes for the three months ended December 30, 2017 was 58.4% . Our effective tax rate for the three months ended December 30, 2017 was higher than the U.S. federal blended tax rate of 24.5% primarily due to the Tax Act's one-time mandatory deemed repatriation transition tax, the impact of income subject to foreign tax rates that are higher than U.S. tax rates, the remeasurement of deferred tax assets and liabilities based on the newly enacted U.S. Federal tax rate of 21.0% , stock-based compensation not deductible for tax purposes and limitations on the deductibility of compensation under IRC Section 162(m). These amounts are partially offset by the excess tax benefits from stock award exercises and restricted stock unit vesting, the benefit of foreign tax credits, the benefit of federal research and development tax credits, the benefit of a domestic manufacturing deduction under IRC Section 199 and our Singapore tax exemption.

Defined Benefit Plans

Defined Benefit Plans	3 Months Ended
	Dec. 29, 2018
Postemployment Benefits [Abstract]
Defined Benefits Plans	DEFINED BENEFIT PLANS For the three months ended December 29, 2018 and December 30, 2017 , net periodic cost under our defined benefit plans was $0.6 million and $0.5 million , respectively.

Segment Information

Segment Information	3 Months Ended
	Dec. 29, 2018
Segment Reporting [Abstract]
Segment Information	SEGMENT AND GEOGRAPHIC INFORMATION At December 29, 2018 , we were organized into two reporting segments, OEM Laser Sources ("OLS") and Industrial Lasers & Systems ("ILS"), based upon our organizational structure and how the chief operating decision maker ("CODM") receives and utilizes information provided to allocate resources and make decisions. This segmentation reflects the go-to-market strategies and synergies for our broad portfolio of laser technologies and products. While both segments deliver cost-effective, highly reliable photonics solutions, the OLS business segment is focused on high performance laser sources and complex optical sub-systems, typically used in microelectronics manufacturing, medical diagnostics and therapeutic medical applications, as well as in scientific research. Our ILS business segment delivers high performance laser sources, sub-systems and tools primarily used for industrial laser materials processing, serving important end markets like automotive, machine tool, consumer goods and medical device manufacturing. Ondax’s and OR Laser's operating results have been included in our ILS segment. We have identified OLS and ILS as operating segments for which discrete financial information is available. Both units have dedicated engineering, manufacturing, product business management and product line management functions. A small portion of our outside revenue is attributable to projects and recently developed products for which a segment has not yet been determined. The associated direct and indirect costs are presented in the category of Corporate and other, along with other corporate costs as described below. Our Chief Executive Officer has been identified as the CODM, as he assesses the performance of the segments and decides how to allocate resources to the segments. Income from continuing operations is the measure of profit and loss that our CODM uses to assess performance and make decisions. As assets are not a measure used to assess the performance of the company by the CODM, asset information is not tracked or compiled by segment and is not available to be reported in our disclosures. Income from continuing operations represents the net sales less the cost of sales and direct operating expenses incurred within the operating segments as well as allocated expenses such as shared sales and manufacturing costs. We do not allocate to our operating segments certain operating expenses which we manage separately at the corporate level. These unallocated costs include stock-based compensation and corporate functions (certain research and development, management, finance, legal and human resources) and are included in the results below under Corporate and other in the reconciliation of operating results. Management does not consider unallocated Corporate and other costs in its measurement of segment performance. The following table provides net sales and income from continuing operations for our operating segments and a reconciliation of our total income from continuing operations to income from continuing operations before income taxes (in thousands): Three Months Ended December 29, December 30, Net sales: OEM Laser Sources $ 242,348 $ 325,657 Industrial Lasers & Systems 140,798 151,908 Total net sales $ 383,146 $ 477,565 Income (loss) from continuing operations: OEM Laser Sources $ 78,858 $ 127,717 Industrial Lasers & Systems (13,704 ) 1,213 Corporate and other (12,343 ) (19,607 ) Total income from continuing operations 52,811 109,323 Total other income (expense), net (9,151 ) (8,500 ) Income from continuing operations before income taxes $ 43,660 $ 100,823 Geographic Information Our foreign operations consist primarily of manufacturing facilities and sales offices in Europe and Asia-Pacific. Sales, marketing and customer service activities are conducted through sales subsidiaries throughout the world. Geographic sales information for first quarter of fiscal 2019 and 2018 is based on the location of the end customer. Sales to unaffiliated customers are as follows (in thousands): Three months ended SALES December 29, December 30, United States $ 84,030 $ 71,944 Foreign countries: South Korea 106,526 178,367 China 47,544 77,504 Europe, other 36,289 40,505 Japan 29,837 29,620 Germany 37,885 35,995 Asia-Pacific, other 27,228 29,982 Rest of World 13,807 13,648 Total foreign countries sales 299,116 405,621 Total sales $ 383,146 $ 477,565 Major Customers We had one customer during the three months ended December 29, 2018 and December 30, 2017 that accounted for 18.5% and 32.8% of net sales, respectively. The customer purchased primarily from our OLS segment. We had one customer that accounted for 22.0% and 16.4% of accounts receivable at December 29, 2018 and September 29, 2018 , respectively. We had another customer that accounted for 12.5% and 16.7% of accounts receivable at December 29, 2018 and September 29, 2018 , respectively. The customers purchased primarily from our OLS segment.

Restructuring charges

Restructuring charges	3 Months Ended
	Dec. 29, 2018
Restructuring and Related Activities [Abstract]
Restructuring charges	RESTRUCTURING CHARGES In the first quarter of fiscal 2017, we began the implementation of planned restructuring activities in connection with the acquisition of Rofin. These activities primarily relate to exiting our legacy high power fiber laser product line, change of control payments to Rofin officers, the exiting of two product lines acquired in the acquisition of Rofin, realignment of our supply chain due to segment reorganization and consolidation of sales and distribution offices as well as certain manufacturing sites. These activities resulted in charges primarily for employee termination, other exit related costs associated with the write-off of property and equipment and inventory and early lease termination costs. The following table presents our current liability as accrued on our balance sheets for restructuring charges. The table sets forth an analysis of the components of the restructuring charges and payments and other deductions made against the accrual for the first three months of fiscal 2019 and 2018 (in thousands): Severance Related Asset Write-Offs Other Total Balances, September 29, 2018 $ 836 $ — $ 286 $ 1,122 Provision 212 76 188 476 Payments and other (447 ) (76 ) (244 ) (767 ) Balances, December 29, 2018 $ 601 $ — $ 230 $ 831 Severance Related Asset Write-Offs Other Total Balances, September 30, 2017 $ 1,301 $ — $ — $ 1,301 Provision 629 430 105 1,164 Payments and other (755 ) (430 ) (105 ) (1,290 ) Balances, December 30, 2017 $ 1,175 $ — $ — $ 1,175 At December 29, 2018 , $0.8 million of accrued severance related costs were included in other current liabilities. The current year severance related, asset write-offs of equipment and other costs are related to the consolidation of certain manufacturing sites. The severance related costs in the first three months of fiscal 2018 are primarily comprised of severance pay for employees being terminated due to the consolidation of certain manufacturing sites. The asset write-offs in the first three months of fiscal 2018 are primarily comprised of write-offs of inventory and equipment due to the consolidation of certain manufacturing sites. By segment, $0.5 million of restructuring costs were incurred in the ILS segment and $0.0 million were incurred in the OLS segment in the three months ended December 29, 2018 , respectively. $0.4 million of restructuring costs were incurred in the ILS segment and $0.8 million were incurred in the OLS segment in the three months ended December 30, 2017 , respectively. Restructuring charges are recorded in cost of sales, research and development and selling, general and administrative expenses in our condensed consolidated statements of operations.

Discontinued Operations and Sal

Discontinued Operations and Sale of Assets Held for sale	3 Months Ended
	Dec. 29, 2018
Discontinued Operations and Disposal Groups [Abstract]
Discontinued Operations and Sale of Assets Held for sale	DISCONTINUED OPERATIONS AND SALE OF ASSETS HELD FOR SALE Discontinued Operations Discontinued operations are from the Hull Business that we acquired as part of our acquisition of Rofin. As a condition of the acquisition, we were required to divest and hold separate the Hull Business and reported this business separately as a discontinued operation until its divestiture. We completed the divestiture of the Hull Business on October 11, 2017, after receiving approval for the terms of the sale from the European Commission. As a result of the divestiture, we recorded a loss in discontinued operations of $2,000 in the first quarter of fiscal 2018. For financial statement purposes, the results of operations for this discontinued business have been segregated from those of the continuing operations and are presented in our condensed consolidated financial statements as discontinued operations. The results from discontinued operations in the first quarter of fiscal 2018 to the date of divestiture (October 11, 2017) were immaterial and were not included in our condensed consolidated results of operations. Sale of Assets Held for Sale In the fourth quarter of fiscal 2017, management decided to sell several entities that we acquired in the Rofin acquisition. Although the sale was not completed as of the end of fiscal 2017, we recorded a non-cash impairment charge of $2.9 million to operating expense in our results of operations in the fourth quarter of fiscal 2017 to reduce our carrying value in these entities to fair value. In the first and second quarters of fiscal 2018, we recorded additional non-cash impairment charges (recoveries) of $0.3 million and $(0.5) million , respectively, to operating expense in our results of operations to reduce our carrying value in these entities to fair value. On April 27, 2018, we completed the sale of these entities acquired in the Rofin acquisition in exchange for cash of $6.3 million and we recognized an additional loss on the sale of $0.5 million in the third quarter of fiscal 2018, for a net loss of $0.3 million in fiscal 2018 related to the sale and impairment of these entities.

Recent Accounting Standards (Po

Recent Accounting Standards (Policies)	3 Months Ended
	Dec. 29, 2018
Accounting Policies [Abstract]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	Adoption of New Accounting Pronouncement In May 2014, the Financial Accounting Standards Board ("the FASB") issued ASC 606, which outlines a single, comprehensive model for entities to use in accounting for revenue arising from contracts with customers. The core principle of ASC 606 is to recognize revenue when promised goods or services are transferred to customers in an amount that reflects the consideration that is expected to be received for those goods or services. ASC 606 defines a five-step process to achieve this core principle and, accordingly, we expect more judgment and estimates may be required within the revenue recognition process than were required under the previous revenue recognition standard, including identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. ASC 606 permits two methods of adoption: retrospectively to each prior reporting period presented (the full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the modified retrospective method). We adopted ASC 606 and all related amendments as of September 30, 2018 using the modified retrospective transition method applied to contracts that were not completed as of September 29, 2018 and all new contracts entered into by us subsequent to September 29, 2018. All prior period financial statements and disclosures are presented in accordance with ASC 605. We concluded that the adoption of the new standard did not have a material impact on the timing or amount of revenue recognized as the majority of our sales are not bundled. Therefore, revenue will be recorded at the point-in-time when control transfers, which is consistent with the timing of revenue recognition under ASC 605. See Note 1, "Basis of Presentation" and Note 3, "Revenue Recognition" to the Notes to Condensed Consolidated Financial Statements for more information. There was no impact on the opening accumulated retained earnings, revenues, costs, deferred income, customer deposits or other balances as of September 30, 2018 or the quarter ended December 29, 2018 due to the adoption of ASC 606. In August 2018, the Securities and Exchange Commission ("SEC") adopted amendments to certain disclosure requirements in Securities Act Release No. 33-10532, Disclosure Update and Simplification. The amendments became effective on November 5, 2018. The SEC staff subsequently indicated that it would not object if a filer’s first presentation of changes in shareholders’ equity is included in its Form 10-Q for the quarter that begins after the final rule’s effective date. Among the amendments is the requirement to present the changes in shareholders’ equity in the interim financial statements (either in a separate statement or footnote) in quarterly reports on Form 10-Q. The analysis should present a reconciliation of the beginning balance to the ending balance of each period for which a consolidated statement of operations is required to be filed. We adopted this amendment and have included the first presentation of changes in stockholders’ equity in this quarterly report on Form 10-Q for our first quarter of fiscal 2019.
Recent Accounting Standards	Recently Issued Accounting Pronouncements In February 2016, the FASB issued accounting guidance that modifies lease accounting for lessees to increase transparency and comparability by recording lease assets and liabilities for operating leases and disclosing key information about leasing arrangements. The new standard will become effective for our fiscal year 2020, which begins on September 29, 2019. We will adopt the new guidance utilizing the modified retrospective transition method. We have reviewed the requirements of this standard and have formulated a plan for implementation. We continue to implement internal controls and key system functionality to enable the preparation of financial information. We expect the standard will have a material impact on our consolidated balance sheets, but will not have a material impact on our consolidated income statements. The most significant impact will be the recognition of Right-Of-Use assets and lease liabilities for operating leases, while our accounting for capital leases will remain substantially unchanged. We will continue to assess and disclose the impact that this new guidance will have on our consolidated financial statements, disclosures and related controls, when known.

Revenue Recogition (Tables)

Revenue Recogition (Tables)	3 Months Ended
	Dec. 29, 2018
Revenue from Contract with Customer [Abstract]
Summary of Revenue from Contracts with Customers	The following tables summarize revenue from contracts with customers (in thousands): Sales by revenue type and segment Three months ended December 29, 2018 December 30, 2017 OEM Laser Sources Industrial Lasers & Systems OEM Laser Sources Industrial Lasers & Systems Net sales: Products (1) $ 152,742 $ 111,975 $ 230,768 $ 118,260 Other product and service revenues (2) 89,606 28,823 94,889 33,648 Total net sales $ 242,348 $ 140,798 $ 325,657 $ 151,908 (1) Net sales primarily recognized at a point in time. (2) Includes sales of spare parts, related accessories and other consumable parts as well as revenues from service agreements, of which $12.6 million for the three months ended December 29, 2018 was recognized over time. Sales by market application and segment Three months ended December 29, 2018 December 30, 2017 OEM Laser Sources Industrial Lasers & Systems OEM Laser Sources Industrial Lasers & Systems Net sales: Microelectronics $ 162,203 $ 16,206 $ 250,237 $ 17,939 Materials processing 8,802 95,841 10,453 117,008 OEM components and instrumentation 39,219 27,134 32,997 15,859 Scientific and government programs 32,124 1,617 31,970 1,102 Total net sales $ 242,348 $ 140,798 $ 325,657 $ 151,908
Summary of Customer Deposits and Deferred Revenue	A rollforward of our customer deposits and deferred revenue is as follows (in thousands): Beginning balance, September 30, 2018 (1) $ 55,637 Amount of customer deposits and deferred revenue recognized in income (50,916 ) Additions to customer deposits and deferred revenue 41,270 Translation adjustments (339 ) Ending balance, December 29, 2018 (2) $ 45,652 (1) Beginning customer deposits and deferred revenue as of September 30, 2018 includes $50,546 of current portion and $5,091 of long-term portion. (2) Ending customer deposits and deferred revenue as of December 29, 2018 includes $40,143 of current portion and $5,509 of long-term portion.
Summary of Estimated Revenue Expected to be Recognized in the Future	The following table includes estimated revenue expected to be recognized in the future related to performance obligations for sales of maintenance agreements, extended warranties, installation, and contracts with customer acceptance provisions included in customer deposits and deferred revenue as of December 29, 2018 (in thousands): Remainder of fiscal 2019 Fiscal 2020 Fiscal 2021 and after Total Performance Obligations $ 37,626 $ 5,177 $ 2,849 $ 45,652

Business Combinations (Tables)

Business Combinations (Tables)	3 Months Ended
	Dec. 29, 2018
Business Combinations [Abstract]
Schedule of Business Acquisitions, by Acquisition	Our allocation of the purchase price is as follows (in thousands): Tangible assets: Cash $ 1,936 Accounts receivable 3,973 Inventories 2,360 Prepaid expenses and other assets 630 Property and equipment 1,515 Liabilities assumed (5,119 ) Deferred tax liabilities (4,517 ) Intangible assets: Existing technology 14,100 Non-competition 200 Backlog 100 Customer relationships 700 Trademarks 50 Goodwill 31,456 Total $ 47,384 Our preliminary allocation of the purchase price is as follows (in thousands): Tangible assets: Property and equipment $ 2,770 Intangible assets: Existing technology 1,600 Customer relationships 230 Production know-how 2,300 Backlog 100 Total $ 7,000 Our preliminary allocation of the purchase price is as follows (in thousands): Tangible assets: Cash $ 103 Accounts receivable 534 Inventories 1,793 Prepaid expenses and other assets 17 Deferred tax assets 458 Property and equipment 122 Liabilities assumed (499 ) Intangible assets: Existing technology 5,600 Customer relationships 300 Goodwill 3,556 Total $ 11,984

Fair Values (Tables)

Fair Values (Tables)	3 Months Ended
	Dec. 29, 2018
Fair Value Disclosures [Abstract]
Schedule of financial assets and liabilities measured at fair value	Financial assets and liabilities measured at fair value as of December 29, 2018 and September 29, 2018 are summarized below (in thousands): Aggregate Fair Value Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs Aggregate Fair Value Quoted Prices in Active Markets for Identical Assets Significant Other Observable Inputs December 29, 2018 September 29, 2018 (Level 1) (Level 2) (Level 1) (Level 2) Assets: Cash equivalents: Money market fund deposits $ 42,679 $ 42,679 $ — $ 56,285 $ 56,285 $ — U.S. Treasury and agency obligations (1) 121 — 121 — — — Commercial paper (1) 1,197 — 1,197 — — — Short-term investments: U.S. Treasury and agency obligations (1) 5,019 — 5,019 120 — 120 Prepaid and other assets: Foreign currency contracts (2) 789 — 789 1,007 — 1,007 Money market fund deposits — Deferred comp and supplemental plan (3) 808 808 — 522 522 — Mutual funds — Deferred comp and supplemental plan (3) 20,467 20,467 — 21,862 21,862 — Total $ 71,080 $ 63,954 $ 7,126 $ 79,796 $ 78,669 $ 1,127 Liabilities: Other current liabilities: Foreign currency contracts (2) (1,361 ) — (1,361 ) (1,879 ) — (1,879 ) Total $ 69,719 $ 63,954 $ 5,765 $ 77,917 $ 78,669 $ (752 ) ___________________________________________________ (1) Valuations are based upon quoted market prices in active markets involving similar assets. The market inputs used to value these instruments generally consist of market yields, reported trades, broker/dealer quotes or alternative pricing sources with reasonable levels of price transparency. Pricing sources include industry standard data providers, security master files from large financial institutions, and other third party sources which are input into a distribution-curve-based algorithm to determine a daily market value. This creates a "consensus price" or a weighted average price for each security. (2) The principal market in which we execute our foreign currency contracts is the institutional market in an over-the-counter environment with a relatively high level of price transparency. The market participants usually are large commercial banks. Our foreign currency contracts’ valuation inputs are based on quoted prices and quoted pricing intervals from public data sources and do not involve management judgment. See Note 7, "Derivative Instruments and Hedging Activities." (3) The fair value of mutual funds is determined based on quoted market prices. Securities traded on a national exchange are stated at the last reported sales price on the day of valuation; other securities traded in over-the-counter markets and listed securities for which no sale was reported on that date are stated as the last quoted bid price.

Short-Term Investments (Tables)

Short-Term Investments (Tables)	3 Months Ended
	Dec. 29, 2018
Cash, Cash Equivalents, and Short-term Investments [Abstract]
Schedule of cash, cash equivalents and short-term investments	Cash, cash equivalents and short-term investments consist of the following (in thousands): December 29, 2018 Cost Basis Unrealized Gains Unrealized Losses Fair Value Cash and cash equivalents $ 314,996 $ 1 $ — $ 314,997 Short-term investments: Available-for-sale securities: U.S. Treasury and agency obligations 5,000 19 — 5,019 Total short-term investments $ 5,000 $ 19 $ — $ 5,019 September 29, 2018 Cost Basis Unrealized Gains Unrealized Losses Fair Value Cash and cash equivalents $ 310,495 $ — $ — $ 310,495 Short-term investments: Available-for-sale securities: U.S. Treasury and agency obligations 120 — — 120 Total short-term investments $ 120 $ — $ — $ 120
Schedule of amortized cost and estimated fair value of available-for-sale investments in debt securities	The amortized cost and estimated fair value of available-for-sale investments in debt securities as of December 29, 2018 and September 29, 2018 classified as short-term investments on our condensed consolidated balance sheet were as follows (in thousands): December 29, 2018 September 29, 2018 Amortized Cost Estimated Fair Value Amortized Cost Estimated Fair Value Investments in available-for-sale debt securities due in less than one year $ 5,000 $ 5,019 $ 120 $ 120

Derivative Instruments and He_2

Derivative Instruments and Hedging Activities (Tables)	3 Months Ended
	Dec. 29, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amounts of Outstanding Derivative Positions	The outstanding notional contract and fair value asset (liability) amounts of non-designated hedge contracts, with maximum maturity of two months, are as follows (in thousands): U.S. Notional Contract Value U.S. Fair Value December 29, 2018 September 29, 2018 December 29, 2018 September 29, 2018 Euro currency hedge contracts Purchase $ 135,736 $ 126,589 $ 611 $ (1,554 ) Sell $ (7,134 ) $ (8,701 ) $ (31 ) 43 Japanese Yen currency hedge contracts Purchase $ 2,288 $ — $ 36 $ — Sell $ (41,210 ) $ (27,473 ) $ (809 ) $ 637 South Korean Won currency hedge contracts Purchase $ 1,660 $ 2,778 $ (16 ) $ 27 Sell $ (39,665 ) $ (31,920 ) $ (147 ) $ (109 ) Chinese RMB currency hedge contracts Purchase $ 2,191 $ 5,852 $ (16 ) $ (33 ) Sell $ (37,938 ) $ (51,137 ) $ (331 ) $ 300 Singapore Dollar currency hedge contracts Purchase $ 34,687 $ 30,127 $ 69 $ (131 ) Other foreign currency hedge contracts Purchase $ 5,682 $ 4,091 $ 21 $ (13 ) Sell $ (7,387 ) $ (5,934 ) $ 41 $ (39 )

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Dec. 29, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of changes in carrying amount of goodwill by segment	The changes in the carrying amount of goodwill by segment for the period from September 29, 2018 to December 29, 2018 are as follows (in thousands): OEM Laser Sources Industrial Lasers & Systems Total Balance as of September 29, 2018 $ 100,732 $ 342,208 $ 442,940 Additions (see Note 4) — 3,556 3,556 Translation adjustments and other (1,106 ) (3,154 ) (4,260 ) Balance as of December 29, 2018 $ 99,626 $ 342,610 $ 442,236
Schedule of components of amortizable intangible assets	Components of our amortizable intangible assets are as follows (in thousands): December 29, 2018 September 29, 2018 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Existing technology $ 206,454 $ (104,889 ) $ 101,565 $ 201,759 $ (94,376 ) $ 107,383 Customer relationships 49,238 (23,384 ) 25,854 50,359 (22,383 ) 27,976 Trade name 5,788 (4,233 ) 1,555 5,888 (3,818 ) 2,070 Production know-how 2,300 (114 ) 2,186 — — — In-process research & development 4,781 — 4,781 4,864 — 4,864 Total $ 268,561 $ (132,620 ) $ 135,941 $ 262,870 $ (120,577 ) $ 142,293
Schedule of estimated amortization expense	At December 29, 2018 , estimated amortization expense for the remainder of fiscal 2019 , the next five succeeding fiscal years and all fiscal years thereafter are as follows (in thousands): Estimated Amortization Expense 2019 (remainder) $ 42,342 2020 49,637 2021 18,328 2022 7,188 2023 4,491 2024 3,108 Thereafter 6,066 Total (excluding IPR&D) $ 131,160

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	3 Months Ended
	Dec. 29, 2018
Balance Sheet Related Disclosures [Abstract]
Schedule of inventories	Inventories consist of the following (in thousands): December 29, September 29, Purchased parts and assemblies $ 148,940 $ 137,566 Work-in-process 178,947 186,240 Finished goods 165,269 162,935 Total inventories $ 493,156 $ 486,741
Schedule of prepaid expenses and other assets	Prepaid expenses and other assets consist of the following (in thousands): December 29, September 29, Prepaid and refundable income taxes $ 39,165 $ 37,884 Other taxes receivable 15,267 16,930 Prepaid expenses and other assets 29,709 30,266 Total prepaid expenses and other assets $ 84,141 $ 85,080
Schedule of other assets	Other assets consist of the following (in thousands): December 29, September 29, Assets related to deferred compensation arrangements $ 35,465 $ 37,370 Deferred tax assets 65,043 64,858 Other assets (1) 12,448 9,521 Total other assets $ 112,956 $ 111,749
Schedule of other current liabilities	Other current liabilities consist of the following (in thousands): December 29, September 29, Accrued payroll and benefits $ 45,044 $ 55,704 Deferred revenue 21,997 30,613 Warranty reserve 40,489 40,220 Accrued expenses and other 35,725 36,859 Customer deposits 18,146 19,933 Total other current liabilities $ 161,401 $ 183,329
Schedule of components of reserve for warranty costs	Components of the reserve for warranty costs during the first three months of fiscal 2019 and 2018 were as follows (in thousands): Three Months Ended December 29, December 30, Beginning balance $ 40,220 $ 36,149 Additions related to current period sales 17,081 14,140 Warranty costs incurred in the current period (16,376 ) (12,404 ) Accruals resulting from acquisitions 21 — Adjustments to accruals related to foreign exchange and other (457 ) (76 ) Ending balance $ 40,489 $ 37,809
Schedule of other long-term liabilities	Other long-term liabilities consist of the following (in thousands): December 29, September 29, Long-term taxes payable $ 35,709 $ 36,336 Deferred compensation 39,021 40,895 Defined benefit plan liabilities 37,873 37,528 Deferred tax liabilities 21,615 26,339 Deferred revenue 5,509 5,091 Asset retirement obligations liability 4,551 4,529 Other long-term liabilities 1,235 1,238 Total other long-term liabilities $ 145,513 $ 151,956

Borrowings (Tables)

Borrowings (Tables)	3 Months Ended
	Dec. 29, 2018
Debt Disclosure [Abstract]
Schedule of Short-term Debt	Short-term borrowings and current portion of long-term obligations consist of the following (in thousands): December 29, September 29, Current portion of Euro Term Loan (1) $ 3,065 $ 3,092 1.3% Term loan due 2024 1,783 1,448 1.0% State of Connecticut term loan due 2023 375 374 OR Laser loans 158 158 Capital lease obligations 270 — Line of credit borrowings 41,019 — Total short-term borrowings and current portion of long-term obligations $ 46,670 $ 5,072 (1) Net of debt issuance costs of $4.6 million and $4.7 million at December 29, 2018 and September 29, 2018 , respectively.
Long-term Debt	Long-term obligations consist of the following (in thousands): December 29, September 29, Euro Term Loan due 2024 (1) $ 404,562 $ 411,661 1.3% Term loan due 2024 6,775 7,242 1.0% State of Connecticut term loan due 2023 1,312 1,406 OR Laser loans 364 402 Capital lease obligations 492 — Total long-term obligations $ 413,505 $ 420,711 (1) Net of debt issuance costs of $9.9 million and $11.2 million at December 29, 2018 and September 29, 2018 , respectively.
Schedule of Maturities of Long-term Debt	Contractual maturities of our debt obligations as of December 29, 2018 are as follows (in thousands): Amount 2019 (remainder) $ 7,766 2020 9,823 2021 9,808 2022 9,555 2023 9,461 2024 387,199 Total $ 433,612

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Dec. 29, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of weighted-average assumptions used to estimate fair value of stock options granted and shares purchased	The fair values of shares purchased under the Employee Stock Purchase Plan ("ESPP") for the three months ended December 29, 2018 and December 30, 2017 , respectively, were estimated using the following weighted-average assumptions: Employee Stock Purchase Plan Three Months Ended December 29, December 30, Expected life in years 0.5 0.5 Expected volatility 48.3 % 47.9 % Risk-free interest rate 2.35 % 1.21 % Expected dividend yield — % — % Weighted average fair value per share $ 42.80 $ 70.75
Schedule of weighted average assumptions of performance units	The weighted average fair value for these performance units was determined using a Monte Carlo simulation model incorporating the following weighted average assumptions: Three Months Ended December 29, 2018 December 30, 2017 Risk-free interest rate 2.9 % 1.7 % Volatility 43.7 % 37.0 % Weighted average fair value per share $ 117.43 $ 315.05
Schedule of stock-based compensation expense	The following table shows total stock-based compensation expense and related tax benefits included in the condensed consolidated statements of operations for the three months ended December 29, 2018 and December 30, 2017 (in thousands): Three Months Ended December 29, December 30, Cost of sales $ 1,237 $ 988 Research and development 650 668 Selling, general and administrative 5,989 5,420 Income tax benefit (1,233 ) (1,609 ) $ 6,643 $ 5,467
Schedule of restricted stock award and restricted stock unit activity	The following table summarizes the activity of our time-based and performance restricted stock units for the first three months of fiscal 2019 (in thousands, except per share amounts): Time Based Restricted Stock Units Performance Restricted Stock Units Number of Shares Weighted Average Grant Date Fair Value Number of Shares Weighted Nonvested stock at September 29, 2018 279 $ 155.24 159 $ 155.76 Granted 149 123.26 105 117.43 Vested (1) (155 ) 125.08 (131 ) 74.48 Forfeited (1 ) 189.16 — — Nonvested stock at December 29, 2018 272 $ 154.70 133 $ 184.26 __________________________________________ (1) Service-based restricted stock units vested during the fiscal year. Performance-based restricted stock units included at 100% of target goal; under the terms of the awards, the recipient may earn between 0% and 200% of the award.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Dec. 29, 2018
Earnings Per Share [Abstract]
Schedule of information necessary to calculate basic and diluted earnings (loss) per share	The following table presents information necessary to calculate basic and diluted earnings per share (in thousands, except per share data): Three Months Ended December 29, December 30, Weighted average shares outstanding—basic 24,268 24,635 Dilutive effect of employee stock awards 204 390 Weighted average shares outstanding—diluted 24,472 25,025 Net income from continuing operations $ 35,550 $ 41,903 Loss from discontinued operations, net of income taxes — (2 ) Net income $ 35,550 $ 41,901

Other Income (Expense) (Tables)

Other Income (Expense) (Tables)	3 Months Ended
	Dec. 29, 2018
Other Income and Expenses [Abstract]
Schedule of other nonoperating income (expense)	Other income (expense) is as follows (in thousands): Three Months Ended December 29, December 30, Foreign exchange loss $ (2,177 ) $ (2,235 ) Gain (loss) on deferred compensation investments, net (2,125 ) 1,855 Other (176 ) 156 Other—net $ (4,478 ) $ (224 )

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Dec. 29, 2018
Segment Reporting [Abstract]
Schedule of sales and income (loss) from operations	Sales to unaffiliated customers are as follows (in thousands): Three months ended SALES December 29, December 30, United States $ 84,030 $ 71,944 Foreign countries: South Korea 106,526 178,367 China 47,544 77,504 Europe, other 36,289 40,505 Japan 29,837 29,620 Germany 37,885 35,995 Asia-Pacific, other 27,228 29,982 Rest of World 13,807 13,648 Total foreign countries sales 299,116 405,621 Total sales $ 383,146 $ 477,565 The following table provides net sales and income from continuing operations for our operating segments and a reconciliation of our total income from continuing operations to income from continuing operations before income taxes (in thousands): Three Months Ended December 29, December 30, Net sales: OEM Laser Sources $ 242,348 $ 325,657 Industrial Lasers & Systems 140,798 151,908 Total net sales $ 383,146 $ 477,565 Income (loss) from continuing operations: OEM Laser Sources $ 78,858 $ 127,717 Industrial Lasers & Systems (13,704 ) 1,213 Corporate and other (12,343 ) (19,607 ) Total income from continuing operations 52,811 109,323 Total other income (expense), net (9,151 ) (8,500 ) Income from continuing operations before income taxes $ 43,660 $ 100,823

Restructuring charges (Tables)

Restructuring charges (Tables)	3 Months Ended
	Dec. 29, 2018
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs	The table sets forth an analysis of the components of the restructuring charges and payments and other deductions made against the accrual for the first three months of fiscal 2019 and 2018 (in thousands): Severance Related Asset Write-Offs Other Total Balances, September 29, 2018 $ 836 $ — $ 286 $ 1,122 Provision 212 76 188 476 Payments and other (447 ) (76 ) (244 ) (767 ) Balances, December 29, 2018 $ 601 $ — $ 230 $ 831 Severance Related Asset Write-Offs Other Total Balances, September 30, 2017 $ 1,301 $ — $ — $ 1,301 Provision 629 430 105 1,164 Payments and other (755 ) (430 ) (105 ) (1,290 ) Balances, December 30, 2017 $ 1,175 $ — $ — $ 1,175

Revenue Recogition Disaggregati

Revenue Recogition Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Disaggregation of Revenue [Line Items]
Net sales	$ 383,146	$ 477,565
OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	242,348	325,657
Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	140,798	151,908
Products | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	152,742	230,768
Products | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	111,975	118,260
Services
Disaggregation of Revenue [Line Items]
Net sales	12,600
Microelectronics | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	162,203	250,237
Microelectronics | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	16,206	17,939
Materials processing | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	8,802	10,453
Materials processing | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	95,841	117,008
OEM components and instrumentation | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	39,219	32,997
OEM components and instrumentation | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	27,134	15,859
Scientific and government programs | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	32,124	31,970
Scientific and government programs | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	1,617	1,102
Other products and services [Domain] | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	89,606	94,889
Other products and services [Domain] | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	$ 28,823	$ 33,648

Revenue Recogition Contract bal

Revenue Recogition Contract balances (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2018	Sep. 29, 2018
Change in Contract with Customer, Liability [Abstract]
Contract with customer, beginning balance	$ 55,637
Amount of customer deposits and deferred revenue recognized in income	(50,916)
Additions to customer deposits and deferred revenue	41,270
Translation adjustments	(339)
Contract with customer, ending balance	45,652
Contract with Customer, Liability, Current	40,143	$ 50,546
Customer deposits and deferred revenue, noncurrent	$ 5,509	$ 5,091

Revenue Recogition Performance

Revenue Recogition Performance Obligations (Details) $ in Thousands	Dec. 29, 2018USD ($)
Revenue from Contract with Customer [Abstract]
Performance Obligations	$ 45,652
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-12-29
Revenue from Contract with Customer [Abstract]
Performance Obligations	$ 37,626
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-12-30
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation period	9 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-09-28
Revenue from Contract with Customer [Abstract]
Performance Obligations	$ 5,177
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-09-25
Revenue from Contract with Customer [Abstract]
Performance Obligations	$ 2,849
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation period

Business Combinations - Narrati

Business Combinations - Narrative (Details) - USD ($) $ in Millions	Oct. 05, 2018	Mar. 08, 2018
Ondax Inc.
Business Acquisition [Line Items]
Cost investment	$ 12
Ondax Inc. | Minimum
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life	1 year
Ondax Inc. | Maximum
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life	8 years
Quantum Coating, Inc.
Business Acquisition [Line Items]
Cost investment	$ 7
Quantum Coating, Inc. | Minimum
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life	1 year
Quantum Coating, Inc. | Maximum
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life	5 years
O.R. Lasertechnologies GmbH
Business Acquisition [Line Items]
Cost investment		$ 47.4
O.R. Lasertechnologies GmbH | Minimum
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life		1 year
O.R. Lasertechnologies GmbH | Maximum
Business Acquisition [Line Items]
Finite-Lived Intangible Asset, Useful Life		8 years

Business Combinations - Schedul

Business Combinations - Schedule of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Oct. 05, 2018	Sep. 29, 2018	Mar. 08, 2018
Business Acquisition [Line Items]
Goodwill	$ 442,236		$ 442,940
Ondax Inc.
Business Acquisition [Line Items]
Cash, cash equivalents and short-term investments		$ 103
Accounts receivable		534
Inventory		1,793
Prepaid expenses and other assets		17
Deferred tax assets		458
Property and equipment		122
Liabilities assumed		(499)
Goodwill		3,556
Total		11,984
Ondax Inc. | Existing technology
Business Acquisition [Line Items]
Intangible assets:		5,600
Ondax Inc. | Customer relationships
Business Acquisition [Line Items]
Intangible assets:		300
Quantum Coating, Inc.
Business Acquisition [Line Items]
Property and equipment		2,770
Total		7,000
Quantum Coating, Inc. | Existing technology
Business Acquisition [Line Items]
Intangible assets:		1,600
Quantum Coating, Inc. | Customer relationships
Business Acquisition [Line Items]
Intangible assets:		230
Quantum Coating, Inc. | Production know-how
Business Acquisition [Line Items]
Intangible assets:		2,300
Quantum Coating, Inc. | Backlog
Business Acquisition [Line Items]
Intangible assets:		$ 100
O.R. Lasertechnologies GmbH
Business Acquisition [Line Items]
Cash, cash equivalents and short-term investments				$ 1,936
Accounts receivable				3,973
Inventory				2,360
Prepaid expenses and other assets				630
Property and equipment				1,515
Liabilities assumed				(5,119)
Deferred tax liabilities				(4,517)
Goodwill				31,456
Total				47,384
O.R. Lasertechnologies GmbH | Existing technology
Business Acquisition [Line Items]
Intangible assets:				14,100
O.R. Lasertechnologies GmbH | Non-competition
Business Acquisition [Line Items]
Intangible assets:				200
O.R. Lasertechnologies GmbH | Customer relationships
Business Acquisition [Line Items]
Intangible assets:				700
O.R. Lasertechnologies GmbH | Backlog
Business Acquisition [Line Items]
Intangible assets:				100
O.R. Lasertechnologies GmbH | Trademarks
Business Acquisition [Line Items]
Intangible assets:				$ 50

Fair Values (Details)

Fair Values (Details) - USD ($) $ in Thousands		Dec. 29, 2018	Sep. 29, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Current portion of long term obligation, amortized cost		$ 5,700
Noncurrent portion of long term obligation, amortized cost		413,500
Short-term borrowings and current-portion of long-term obligations		46,670	$ 5,072
Long-term obligations		413,505	420,711
Fair Value, Measurements, Recurring | Prepaid and other assets: | Fair Value, Inputs, Level 1 | Mutual funds — Deferred comp and supplemental plan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds - Deferred comp and supplemental plan	[1]	20,467	21,862
Fair Value, Measurements, Recurring | Prepaid and other assets: | Fair Value, Inputs, Level 2 | Mutual funds — Deferred comp and supplemental plan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds - Deferred comp and supplemental plan	[1]	0	0
Fair Value, Measurements, Recurring | Prepaid and other assets: | Estimate of Fair Value Measurement | Mutual funds — Deferred comp and supplemental plan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds - Deferred comp and supplemental plan	[1]	20,467	21,862
Fair Value, Measurements, Recurring | Assets | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities, fair value disclosure		63,954	78,669
Fair Value, Measurements, Recurring | Assets | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities, fair value disclosure		7,126	1,127
Fair Value, Measurements, Recurring | Assets | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities, fair value disclosure		71,080	79,796
Fair Value, Measurements, Recurring | Other current liabilities: | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities, fair value disclosure		63,954	78,669
Fair Value, Measurements, Recurring | Other current liabilities: | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities, fair value disclosure		5,765	(752)
Fair Value, Measurements, Recurring | Other current liabilities: | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets and liabilities, fair value disclosure		69,719	77,917
Fair Value, Measurements, Recurring | Money market fund deposits | Cash equivalents: | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		42,679	56,285
Fair Value, Measurements, Recurring | Money market fund deposits | Cash equivalents: | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		0	0
Fair Value, Measurements, Recurring | Money market fund deposits | Cash equivalents: | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		42,679	56,285
Fair Value, Measurements, Recurring | Money market fund deposits | Prepaid and other assets: | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	808	522
Fair Value, Measurements, Recurring | Money market fund deposits | Prepaid and other assets: | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	0	0
Fair Value, Measurements, Recurring | Money market fund deposits | Prepaid and other assets: | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[1]	808	522
Fair Value, Measurements, Recurring | U.S. Treasury and agency obligations | Cash equivalents: | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[2]	0	0
Fair Value, Measurements, Recurring | U.S. Treasury and agency obligations | Cash equivalents: | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[2]	121	0
Fair Value, Measurements, Recurring | U.S. Treasury and agency obligations | Cash equivalents: | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[2]	121	0
Fair Value, Measurements, Recurring | U.S. Treasury and agency obligations | Short-term investments: | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[2]	0	0
Fair Value, Measurements, Recurring | U.S. Treasury and agency obligations | Short-term investments: | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[2]	5,019	120
Fair Value, Measurements, Recurring | U.S. Treasury and agency obligations | Short-term investments: | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	[2]	5,019	120
Fair Value, Measurements, Recurring | Commercial paper | Cash equivalents: | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[3]	0	0
Fair Value, Measurements, Recurring | Commercial paper | Cash equivalents: | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[3]	1,197	0
Fair Value, Measurements, Recurring | Commercial paper | Cash equivalents: | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	[3]	1,197	0
Fair Value, Measurements, Recurring | Foreign currency contracts | Prepaid and other assets: | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contracts	[3]	0	0
Fair Value, Measurements, Recurring | Foreign currency contracts | Prepaid and other assets: | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contracts	[3]	789	1,007
Fair Value, Measurements, Recurring | Foreign currency contracts | Prepaid and other assets: | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contracts	[3]	789	1,007
Fair Value, Measurements, Recurring | Foreign currency contracts | Other current liabilities: | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contracts	[1]	0	0
Fair Value, Measurements, Recurring | Foreign currency contracts | Other current liabilities: | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contracts	[1]	(1,361)	(1,879)
Fair Value, Measurements, Recurring | Foreign currency contracts | Other current liabilities: | Estimate of Fair Value Measurement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency contracts	[1]	$ (1,361)	$ (1,879)
[1]	The fair value of mutual funds is determined based on quoted market prices. Securities traded on a national exchange are stated at the last reported sales price on the day of valuation; other securities traded in over-the-counter markets and listed securities for which no sale was reported on that date are stated as the last quoted bid price.
[2]	Valuations are based upon quoted market prices in active markets involving similar assets. The market inputs used to value these instruments generally consist of market yields, reported trades, broker/dealer quotes or alternative pricing sources with reasonable levels of price transparency. Pricing sources include industry standard data providers, security master files from large financial institutions, and other third party sources which are input into a distribution-curve-based algorithm to determine a daily market value. This creates a "consensus price" or a weighted average price for each security.
[3]	The principal market in which we execute our foreign currency contracts is the institutional market in an over-the-counter environment with a relatively high level of price transparency. The market participants usually are large commercial banks. Our foreign currency contracts’ valuation inputs are based on quoted prices and quoted pricing intervals from public data sources and do not involve management judgment. See Note 7, "Derivative Instruments and Hedging Activities.

Short-Term Investments (Details

Short-Term Investments (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Sep. 29, 2018	Dec. 30, 2017
Debt Securities, Available-for-sale [Line Items]
Cash and cash equivalents, Cost Basis	$ 314,996	$ 310,495
Cash and cash equivalent, Unrealized Gains	1	0
Cash and cash equivalent, Unrealized Losses	0	0
Cash and cash equivalents	314,997	310,495	$ 385,735
Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities: Cost Basis	5,000	120
Available-for-sale securities, Unrealized Gains	19	0
Available-for-sale securities, Unrealized Losses	0	0
Available-for-sale securities: Fair Value	5,019	120
Short-term investments: | U.S. Treasury and agency obligations
Debt Securities, Available-for-sale [Line Items]
Available-for-sale securities: Cost Basis	5,000	120
Available-for-sale securities, Unrealized Gains	19	0
Available-for-sale securities, Unrealized Losses	0	0
Available-for-sale securities: Fair Value	$ 5,019	$ 120

Short-Term Investments - Availa

Short-Term Investments - Available-for-sale investments fair value (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 30, 2017	Dec. 29, 2018	Sep. 29, 2018
Cash, Cash Equivalents, and Short-term Investments [Abstract]
Investments in available-for-sale debt securities due in less than one year - Amortized Cost		$ 5,000	$ 120
Investments in available-for-sale debt securities in less than one year - Estimated Fair Value		$ 5,019	$ 120
Proceeds from Sale of Debt Securities, Available-for-sale	$ 2,400

Derivative Instruments and He_3

Derivative Instruments and Hedging Activities - Notional and Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Sep. 29, 2018
Derivatives, Fair Value [Line Items]
Gain (loss) on derivatives	$ (3,700)	$ (2,600)
Not Designated as Hedging Instrument | Purchase | Other Foreign Currency Hedge
Derivatives, Fair Value [Line Items]
Derivative asset, notional amount	5,682		$ 4,091
Derivative asset, Fair Value	21		(13)
Not Designated as Hedging Instrument | Purchase | Euro Member Countries, Euro
Derivatives, Fair Value [Line Items]
Derivative asset, notional amount	135,736		126,589
Derivative asset, Fair Value	611		(1,554)
Not Designated as Hedging Instrument | Purchase | Japan, Yen
Derivatives, Fair Value [Line Items]
Derivative asset, notional amount	2,288		0
Derivative asset, Fair Value	36		0
Not Designated as Hedging Instrument | Purchase | Korea (South), Won
Derivatives, Fair Value [Line Items]
Derivative asset, notional amount	1,660		2,778
Derivative asset, Fair Value	(16)		27
Not Designated as Hedging Instrument | Purchase | China, Yuan Renminbi
Derivatives, Fair Value [Line Items]
Derivative asset, notional amount	2,191		5,852
Derivative asset, Fair Value	(16)		(33)
Not Designated as Hedging Instrument | Purchase | Singapore, Dollars
Derivatives, Fair Value [Line Items]
Derivative asset, notional amount	34,687		30,127
Derivative asset, Fair Value	69		(131)
Not Designated as Hedging Instrument | Sell | Other Foreign Currency Hedge
Derivatives, Fair Value [Line Items]
Derivative liability, notional amount	(7,387)		(5,934)
Derivative liability, Fair Value	41		(39)
Not Designated as Hedging Instrument | Sell | Euro Member Countries, Euro
Derivatives, Fair Value [Line Items]
Derivative liability, notional amount	(7,134)		(8,701)
Derivative liability, Fair Value	(31)		43
Not Designated as Hedging Instrument | Sell | Japan, Yen
Derivatives, Fair Value [Line Items]
Derivative liability, notional amount	(41,210)		(27,473)
Derivative liability, Fair Value	(809)		637
Not Designated as Hedging Instrument | Sell | Korea (South), Won
Derivatives, Fair Value [Line Items]
Derivative liability, notional amount	(39,665)		(31,920)
Derivative liability, Fair Value	(147)		(109)
Not Designated as Hedging Instrument | Sell | China, Yuan Renminbi
Derivatives, Fair Value [Line Items]
Derivative liability, notional amount	(37,938)		(51,137)
Derivative liability, Fair Value	$ (331)		$ 300

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Goodwill (Details) $ in Thousands	3 Months Ended
	Dec. 29, 2018USD ($)
Goodwill [Roll Forward]
Goodwill, beginning of period	$ 442,940
Additions	3,556
Translation adjustments and other	(4,260)
Goodwill, end of period	442,236
OEM Laser Sources
Goodwill [Roll Forward]
Goodwill, beginning of period	100,732
Additions	0
Translation adjustments and other	(1,106)
Goodwill, end of period	99,626
Industrial Lasers & Systems
Goodwill [Roll Forward]
Goodwill, beginning of period	342,208
Additions	3,556
Translation adjustments and other	(3,154)
Goodwill, end of period	$ 342,610

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Sep. 29, 2018
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	$ 268,561		$ 262,870
Accumulated Amortization	(132,620)		(120,577)
Net including IPRD	135,941		142,293
Amortization expense for intangible assets	15,067	$ 15,100
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]
2019 (remainder)	42,342
2,020	49,637
2,021	18,328
2,022	7,188
2,023	4,491
2,024	3,108
Thereafter	6,066
Net excluding IPRD	131,160
Existing technology
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	206,454		201,759
Accumulated Amortization	(104,889)		(94,376)
Net including IPRD	101,565		107,383
Customer relationships
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	49,238		50,359
Accumulated Amortization	(23,384)		(22,383)
Net including IPRD	25,854		27,976
Trade name
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	5,788		5,888
Accumulated Amortization	(4,233)		(3,818)
Net including IPRD	1,555		2,070
Production know-how
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	2,300		0
Accumulated Amortization	(114)		0
Net including IPRD	2,186		0
In-process research & development
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	4,781		4,864
Accumulated Amortization	0		0
Net including IPRD	4,781		$ 4,864
Foreign Exchange
Finite-Lived Intangible Assets, Net [Abstract]
Amortization expense for intangible assets	$ 2,400	$ 100

Balance Sheet Details (Details)

Balance Sheet Details (Details) $ in Thousands, € in Millions	3 Months Ended
	Dec. 29, 2018EUR (€)	Dec. 29, 2018USD ($)	Dec. 30, 2017USD ($)	Sep. 29, 2018USD ($)
Inventory, Net [Abstract]
Purchased parts and assemblies		$ 148,940		$ 137,566
Work-in-process		178,947		186,240
Finished goods		165,269		162,935
Total inventories		493,156		486,741
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid and refundable income taxes		39,165		37,884
Other taxes receivable		15,267		16,930
Prepaid expenses and other assets		29,709		30,266
Total prepaid expenses and other assets		84,141		85,080
Other Assets, Noncurrent Disclosure [Abstract]
Assets related to deferred compensation arrangements		35,465		37,370
Deferred tax assets		65,043		64,858
Other assets (1)		12,448		9,521
Total other assets		112,956		111,749
Payments to acquire investments	€ 3	3,400
Other Liabilities, Current [Abstract]
Accrued payroll and benefits		45,044		55,704
Deferred revenue		21,997		30,613
Warranty reserve		40,489		40,220
Accrued expenses and other		35,725		36,859
Customer deposits		18,146		19,933
Total other current liabilities		161,401		183,329
Movement in Standard and Extended Product Warranty Accrual, Increase (Decrease) [Roll Forward]
Beginning balance		40,220	$ 36,149
Additions related to current period sales		17,081	14,140
Warranty costs incurred in the current period		(16,376)	(12,404)
Accruals resulting from acquisitions		21	0
Adjustments to accruals related to foreign exchange and other		(457)	(76)
Ending balance		40,489	$ 37,809
Other Liabilities, Noncurrent [Abstract]
Long-term taxes payable		35,709		36,336
Deferred compensation		39,021		40,895
Defined benefit plan liabilities		37,873		37,528
Deferred tax liabilities		21,615		26,339
Deferred revenue		5,509		5,091
Asset retirement obligations liability		4,551		4,529
Other long-term liabilities		1,235		1,238
Total other long-term liabilities		$ 145,513		$ 151,956

Borrowings (Details)

Borrowings (Details) € in Millions	May 08, 2018	Jul. 01, 2017USD ($)	Dec. 29, 2018EUR (€)	Dec. 29, 2018USD ($)	Sep. 29, 2018USD ($)	Nov. 07, 2016EUR (€)	Nov. 07, 2016USD ($)
Debt [Line Items]
Total short-term borrowings and current portion of long-term obligations				$ 46,670,000	$ 5,072,000
Debt issuance cost related to repricing		$ 500,000
Additional sources of cash available				26,400,000
Debt Instrument, Unused Borrowing Capacity, Amount				18,000,000
Rofin-Sinar
Debt [Line Items]
Lines of credit, maximum borrowing capacity							$ 30,000,000
Swing line, maximum borrowing capacity							$ 10,000,000
Credit Agreement November 7 2016
Debt [Line Items]
Senior secured net leverage ratio to maintain compliance on the loan each quarter end						3.50	3.50
Euro Member Countries, Euro
Debt [Line Items]
Domestic line of credit drawn | €						€ 10
Euro term loan
Debt [Line Items]
Debt Issuance Costs for revolving credit facility		$ 28,500,000
Amortization period of the debt issuance cost		7 years
Euro term loan | Minimum | Eurodollar
Debt [Line Items]
Debt Instrument, Interest Rate, Stepdown	1.00%
Euro term loan | Maximum | Eurodollar
Debt [Line Items]
Debt Instrument, Interest Rate, Stepdown	2.00%
Euro term loan | Euro Member Countries, Euro
Debt [Line Items]
Forward contract purchased for the term loan | €			€ 369.9			€ 670
Additional Euro currency rate						0.01	0.01
Quarter principal payment requirement for Euro term loan						0.0025	0.0025
Euro term loan | Euro Member Countries, Euro | Minimum
Debt [Line Items]
Applicable margin for Eurocurrency rate loan						0.0375	0.0375
Revolving line of credit
Debt [Line Items]
Revolving facility to finance acquisition of Rofin			€ 10				$ 100,000,000
Revolving facility to finance acquisition of Rofin, outstanding balance				40,000,000
Additional base rate						0.005	0.005
Debt Issuance Costs for revolving credit facility		$ 2,300,000
debt issuance cost amortization period		5 years
Revolving line of credit | Minimum
Debt [Line Items]
Applicable margin for base rate revolving loan						0.0275	0.0275
Commitment fee accrues range on unused portion of revolving loan						0.00375	0.00375
Revolving line of credit | Maximum
Debt [Line Items]
Commitment fee accrues range on unused portion of revolving loan						0.005	0.005
Line of Credit, Foreign | Europe, other
Debt [Line Items]
Amounts drawn upon line of credit				7,400,000
Line of Credit, Foreign | Japan
Debt [Line Items]
Amounts drawn upon line of credit				$ 1,000,000

Borrowings - Borrowings obligat

Borrowings - Borrowings obligation table (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 29, 2018	Sep. 29, 2018
Short-term Debt [Line Items]
Total short-term borrowings and current portion of long-term obligations	$ 46,670	$ 5,072
Euro term loan
Short-term Debt [Line Items]
Debt issuance cost for long term portion of the Euro term loan	9,900	11,200
Euro term loan
Short-term Debt [Line Items]
Debt issuance cost for short term Euro term loan	4,600	4,700
Short-term Debt
Short-term Debt [Line Items]
Euro Term Loan due 2024	3,065	3,092
1.3% Term loan due 2024	1,783	1,448
1.0% State of Connecticut term loan due 2023	375	374
OR Laser loans	158	158
Capital lease obligations	270	0
Line of credit borrowings	41,019	0
Total short-term borrowings and current portion of long-term obligations	46,670	5,072
Long-term Debt
Short-term Debt [Line Items]
Euro Term Loan due 2024	404,562	411,661
1.3% Term loan due 2024	6,775	7,242
1.0% State of Connecticut term loan due 2023	1,312	1,406
OR Laser loans	364	402
Capital lease obligations	492	0
Long-term Debt	$ 413,505	$ 420,711

Borrowings - Debt Maturity Tabl

Borrowings - Debt Maturity Table (Details) $ in Thousands	Dec. 29, 2018USD ($)
Debt Disclosure [Abstract]
2019 (remainder)	$ 7,766
2,020	9,823
2,021	9,808
2,022	9,555
2,023	9,461
2,024	387,199
Total contractual obligation due amount	$ 433,612

Stock-Based Compensation - Fair

Stock-Based Compensation - Fair Value of Stock Compensation (Details) - $ / shares	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Common shares that restricted stock units with each unit representing	1
Requisite service period	3 years
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected life in years	6 months	6 months
Expected volatility	48.30%	47.90%
Risk-free interest rate	2.35%	1.21%
Expected dividend yield	0.00%	0.00%
Weighted average fair value per share	$ 42.80	$ 70.75
Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected volatility	43.70%	37.00%
Risk-free interest rate	2.90%	1.70%
Weighted average fair value per share	$ 117.43	$ 315.05

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated stock-based compensation expense	$ 6,643	$ 5,467
Capitalized share-based compensation costs	1,200	1,000
Amortization of capitalized share-based compensation expenses	1,200	1,000
Total compensation cost, unvested stock-based awards granted but not yet recognized	$ 51,600
Total compensation cost, weighted-average period of amortization (in years)	1 year 7 months 12 days
Period End
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Capitalized share-based compensation remaining	$ 1,400	1,300
Cost of sales
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated stock-based compensation expense	1,237	988
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated stock-based compensation expense	650	668
Selling, general and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated stock-based compensation expense	5,989	5,420
Income tax benefit
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Income tax benefit	$ (1,233)	$ (1,609)

Stock-Based Compensation - St_2

Stock-Based Compensation - Stock Options and Awards Activity (Details) shares in Thousands	3 Months Ended
	Dec. 29, 2018$ / sharesshares
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested stock, beginning of period (in shares) | shares	279
Granted (in shares) | shares	149
Vested (in shares) | shares	(155)	[1]
Forfeited (in shares) | shares	(1)
Nonvested stock, end of period (in shares) | shares	272
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested stock, beginning of period (in dollars per share) | $ / shares	$ 155.24
Granted (in dollars per share) | $ / shares	123.26
Vested (in dollars per share) | $ / shares	125.08	[1]
Forfeited (in dollars per share) | $ / shares	189.16
Nonvested stock, end of period (in dollars per share) | $ / shares	$ 154.70
Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested [Roll Forward]
Nonvested stock, beginning of period (in shares) | shares	159
Granted (in shares) | shares	105
Vested (in shares) | shares	(131)	[1]
Forfeited (in shares) | shares	0
Nonvested stock, end of period (in shares) | shares	133
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested stock, beginning of period (in dollars per share) | $ / shares	$ 155.76
Granted (in dollars per share) | $ / shares	117.43
Vested (in dollars per share) | $ / shares	74.48	[1]
Forfeited (in dollars per share) | $ / shares	0
Nonvested stock, end of period (in dollars per share) | $ / shares	$ 184.26
Restricted Stock Units and Awards [Abstract]
Targeted goal of performance based awards and units	100.00%
Performance Restricted Stock Units | Minimum
Restricted Stock Units and Awards [Abstract]
Percentage of performance-based awards earned by recipient	0.00%
Performance Restricted Stock Units | Maximum
Restricted Stock Units and Awards [Abstract]
Percentage of performance-based awards earned by recipient	200.00%
[1]	Service-based restricted stock units vested during the fiscal year. Performance-based restricted stock units included at 100% of target goal; under the terms of the awards, the recipient may earn between 0% and 200% of the award.

Stock Repurchases (Details)

Stock Repurchases (Details) - USD ($)	3 Months Ended
	Dec. 29, 2018	Oct. 28, 2018	Feb. 06, 2018
Feb 2018 repurchase program
Class of Stock [Line Items]
Stock repurchase program, authorized amount			$ 100,000,000
Stock repurchased and retired during period (in shares)	574,946
Stock repurchase, price paid per share (in dollars per share)	$ 173.91
Total cost of stock repurchased, net	$ 100,000,000
Oct 2018 repurchase program
Class of Stock [Line Items]
Stock repurchase program, authorized amount		$ 250,000,000
Stock repurchased and retired during period (in shares)	194,801
Stock repurchase, price paid per share (in dollars per share)	$ 130.91
Total cost of stock repurchased, net	$ 25,500,000
Repurchase limit per quarter		$ 75,000,000

Earnings Per Share (Details)

Earnings Per Share (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Earnings Per Share, Basic and Diluted [Abstract]
Weighted average shares outstanding—basic (in shares)	24,268,000	24,635,000
Dilutive effect of employee stock awards (in shares)	204,000	390,000
Weighted average shares outstanding—diluted (in shares)	24,472,000	25,025,000
Net income from continuing operations	$ 35,550	$ 41,903
Loss from discontinued operations, net of income taxes	0	(2)
Net income	$ 35,550	$ 41,901
Earnings Per Share, Diluted, Other Disclosures [Abstract]
Dilutive securities excluded from calculation of dilutive shares	100,520	19,375

Other Income (Expense) (Details

Other Income (Expense) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Component of Other Income (Expense), Nonoperating [Line Items]
Other - net	$ (4,478)	$ (224)
Foreign exchange loss
Component of Other Income (Expense), Nonoperating [Line Items]
Foreign exchange loss	(2,177)	(2,235)
Gain (loss) on deferred compensation investments, net
Component of Other Income (Expense), Nonoperating [Line Items]
Gain (loss) on deferred compensation investments, net	(2,125)	1,855
Other
Component of Other Income (Expense), Nonoperating [Line Items]
Other	$ (176)	$ 156

Income Taxes (Details)

Income Taxes (Details)	Dec. 22, 2017	Dec. 29, 2018	Dec. 30, 2017
Income Tax Disclosure [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	24.50%
Effective income tax rate (percent)		18.60%	58.40%

Defined Benefit Plans (Details)

Defined Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Postemployment Benefits [Abstract]
Net periodic pension cost	$ 0.6	$ 0.5

Segment Information - Sales and

Segment Information - Sales and Income (Loss) from Operations (Details) $ in Thousands	3 Months Ended
	Dec. 29, 2018USD ($)segments	Dec. 30, 2017USD ($)
Segment Reporting [Abstract]
Number of reporting segments | segments	2
Segment Reporting Information [Line Items]
Net sales	$ 383,146	$ 477,565
Income from operations before other income, income taxes and loss from discontinued operations	52,811	109,323
Total other income (expense), net	(9,151)	(8,500)
Income from continuing operations before income taxes	43,660	100,823
OEM Laser Sources
Segment Reporting Information [Line Items]
Net sales	242,348	325,657
Income (loss) from continuing operations:	78,858	127,717
Industrial Lasers & Systems
Segment Reporting Information [Line Items]
Net sales	140,798	151,908
Income (loss) from continuing operations:	(13,704)	1,213
Corporate and other
Segment Reporting Information [Line Items]
Income (loss) from continuing operations:	$ (12,343)	$ (19,607)

Segment Information Schedule of

Segment Information Schedule of sales by geographic regions (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Geographic information [Line Items]
Net sales	$ 383,146	$ 477,565
United States
Geographic information [Line Items]
Net sales	84,030	71,944
Total foreign countries sales
Geographic information [Line Items]
Net sales	299,116	405,621
South Korea
Geographic information [Line Items]
Net sales	106,526	178,367
China
Geographic information [Line Items]
Net sales	47,544	77,504
Europe, other
Geographic information [Line Items]
Net sales	36,289	40,505
Japan
Geographic information [Line Items]
Net sales	29,837	29,620
Germany
Geographic information [Line Items]
Net sales	37,885	35,995
Asia-Pacific, other
Geographic information [Line Items]
Net sales	27,228	29,982
Rest of World
Geographic information [Line Items]
Net sales	$ 13,807	$ 13,648

Segment Information - Major Cus

Segment Information - Major Customers (Details) - Customer Concentration Risk	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Sales | Customer 1
Concentration Risk [Line Items]
Concentration Risk, Percentage	18.50%	32.80%
Accounts receivable | Customer 1
Concentration Risk [Line Items]
Concentration Risk, Percentage	22.00%	16.40%
Accounts receivable | Customer 2
Concentration Risk [Line Items]
Concentration Risk, Percentage	12.50%	16.70%

Restructuring charges (Details)

Restructuring charges (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 29, 2018	Dec. 30, 2017
Restructuring Reserve [Roll Forward]
Starting balance	$ 1,122	$ 1,301
Provision	476	1,164
Payments and other	(767)	(1,290)
Ending balance	831	1,175
Severance Related
Restructuring Reserve [Roll Forward]
Starting balance	836	1,301
Provision	212	629
Payments and other	(447)	(755)
Ending balance	601	1,175
Severance Related | Industrial Lasers & Systems
Restructuring Reserve [Roll Forward]
Restructuring cost incurred	500	400
Severance Related | OEM Laser Sources
Restructuring Reserve [Roll Forward]
Restructuring cost incurred	0	800
Severance Related | Other current liabilities:
Restructuring Reserve [Roll Forward]
Ending balance	800
Asset Write-Offs
Restructuring Reserve [Roll Forward]
Starting balance	0	0
Provision	76	430
Payments and other	(76)	(430)
Ending balance	0	0
Other
Restructuring Reserve [Roll Forward]
Starting balance	286	0
Provision	188	105
Payments and other	(244)	(105)
Ending balance	$ 230	$ 0

Discontinued Operations and S_2

Discontinued Operations and Sale of Assets Held for sale - Held for sale current assets and liabilities from discontinued operations (Details) - USD ($) $ in Thousands	Apr. 27, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Sep. 29, 2018
Discontinued Operations and Disposal Groups [Abstract]
Gain (loss) in discontinued operations				$ (2)
Non cash impairment charge to reduce carrying value of the acquired entities to fair value			$ (500)	$ 300	$ 2,900
Sale proceeds from sale of entities acquired in Rofin acquisition	$ 6,300
Loss on sale of Rofin entities		$ 500				$ 300