Segment and Geographic Information (Details)	3 Months Ended	12 Months Ended
	Apr. 04, 2020 USD ($)	Oct. 02, 2021 USD ($) segment	Oct. 03, 2020 USD ($)	Sep. 28, 2019 USD ($)
Segment Reporting Information [Line Items]
Number of reporting segments | segment		2
Net sales		$ 1,487,468,000	$ 1,228,999,000	$ 1,430,640,000
Income (loss) from operations:		(98,213,000)	(430,180,000)	83,095,000
Total other expense, net		(17,325,000)	(12,543,000)	(23,047,000)
Income (loss) before income taxes		(115,538,000)	(442,723,000)	60,048,000
Impairment of goodwill		0	327,203,000	0
Asset impairment charges	$ 2,500,000
Merger and acquisition costs		236,047,000	$ 0	$ 0
Termination fee		$ 217,600,000
Sales | Customer concentration risk | Customer one
Segment Reporting Information [Line Items]
Concentration risk, percentage		15.90%	17.20%	16.80%
OEM Laser Sources
Segment Reporting Information [Line Items]
Net sales		$ 913,636,000	$ 758,929,000	$ 886,676,000
Impairment of goodwill	0		0
Industrial Lasers & System
Segment Reporting Information [Line Items]
Net sales		573,832,000	470,070,000	543,964,000
Impairment of goodwill	327,200,000		327,203,000
Industrial Lasers & System | Finite-Lived Intangible Assets
Segment Reporting Information [Line Items]
Asset impairment charges	33,900,000
Industrial Lasers & System | Property and equipment
Segment Reporting Information [Line Items]
Asset impairment charges	85,600,000
Industrial Lasers & System | Right-Of-Use Assets
Segment Reporting Information [Line Items]
Asset impairment charges	$ 1,800,000
Operating Segments | OEM Laser Sources
Segment Reporting Information [Line Items]
Net sales		913,636,000	758,929,000	886,676,000
Income (loss) from operations:		214,003,000	169,883,000	239,073,000
Operating Segments | Industrial Lasers & System
Segment Reporting Information [Line Items]
Net sales		573,832,000	470,070,000	543,964,000
Income (loss) from operations:		13,257,000	(518,186,000)	(93,133,000)
Corporate
Segment Reporting Information [Line Items]
Income (loss) from operations:		$ (325,473,000)	$ (81,877,000)	$ (62,845,000)