Segment and Geographic Information - Sales and Income (Loss) from Operations (Details) $ in Thousands		3 Months Ended	9 Months Ended
Apr. 04, 2020 segments	Jul. 04, 2020 USD ($)	Jun. 29, 2019 USD ($)	Jul. 04, 2020 USD ($)	Jun. 29, 2019 USD ($)
Segment Reporting [Abstract]
Number of reporting segments \| segments	2
Segment Reporting Information [Line Items]
Net sales		$ 298,330	$ 339,170	$ 912,248	$ 1,095,176
Total income (loss) from operations		(1,174)	(7,157)	(439,895)	74,521
Total other expense, net		(4,282)	(4,386)	(12,979)	(17,789)
Income (loss) before income taxes		(5,456)	(11,543)	(452,874)	56,732
OEM Laser Sources
Segment Reporting Information [Line Items]
Net sales		184,694	206,285	559,364	680,230
Income (loss) from operations:		42,853	48,310	126,030	190,003
Industrial Lasers & Systems
Segment Reporting Information [Line Items]
Net sales		113,636	132,885	352,884	414,946
Income (loss) from operations:		(20,571)	(39,569)	(512,716)	(70,925)
Corporate and other
Segment Reporting Information [Line Items]
Income (loss) from operations:		$ (23,456)	$ (15,898)	$ (53,209)	$ (44,557)

Income from operations before other income, income taxes and loss from discontinued operations

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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The net result for the period of deducting operating expenses from operating revenues.

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The net amount of other operating income and expenses, the components of which are not separately disclosed on the income statement, from items that are associated with the entity's normal revenue producing operations.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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