For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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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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Segment and Geographic Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Oct. 03, 2020	Jul. 04, 2020	Apr. 04, 2020	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 29, 2018	Oct. 03, 2020	Sep. 28, 2019	Sep. 29, 2018
Segment Reporting Information [Line Items]
Net sales	$ 316,751	$ 298,330	$ 293,147	$ 320,771	$ 335,464	$ 339,170	$ 372,860	$ 383,146	$ 1,228,999	$ 1,430,640	$ 1,902,573
Income (loss) from continuing operations:									(430,180)	83,095	393,017
Total other expense, net									(12,543)	(23,047)	(31,462)
Income (loss) from continuing operations before income taxes									$ (442,723)	$ 60,048	$ 361,555
Sales \| Customer concentration risk \| Customer one
Segment Reporting Information [Line Items]
Concentration risk, percentage									17.20%	16.80%	25.80%
Accounts receivable \| Customer one
Segment Reporting Information [Line Items]
Concentration risk, percentage									23.90%	28.60%
OEM Laser Sources
Segment Reporting Information [Line Items]
Net sales									$ 758,929	$ 886,676	$ 1,259,477
Industrial Lasers & Systems
Segment Reporting Information [Line Items]
Net sales									470,070	543,964	643,096
Operating Segments \| OEM Laser Sources
Segment Reporting Information [Line Items]
Net sales									758,929	886,676	1,259,477
Income (loss) from continuing operations:									169,883	239,073	469,835
Operating Segments \| Industrial Lasers & Systems
Segment Reporting Information [Line Items]
Net sales									470,070	543,964	643,096
Income (loss) from continuing operations:									(518,186)	(93,133)	(3,687)
Corporate
Segment Reporting Information [Line Items]
Income (loss) from continuing operations:									$ (81,877)	$ (62,845)	$ (73,131)