Goodwill and Intangible Assets - Schedule of changes in carrying amount of goodwill by segment (Details) - USD ($) $ in Thousands		12 Months Ended
		Oct. 03, 2020	Sep. 28, 2019	Sep. 29, 2018
Goodwill [Line Items]
Goodwill		$ 101,317	$ 427,101	$ 442,940
Additions			3,333
Impairment of goodwill		(327,203)
Translation adjustments		1,419	(19,172)
Industrial Lasers & Systems
Goodwill [Line Items]
Goodwill	[1]	0	330,281	342,208
Additions	[1]		3,333
Impairment of goodwill		(327,203)
Translation adjustments	[1]	(3,078)	(15,260)
Goodwill, gross		340,200	343,300
Goodwill, impaired, accumulated impairment loss		340,200
OEM Laser Sources
Goodwill [Line Items]
Goodwill	[2]	101,317	96,820	$ 100,732
Additions	[2]		0
Impairment of goodwill		0
Translation adjustments	[2]	4,497	(3,912)
Goodwill, gross		110,000	$ 105,500
Goodwill, impaired, accumulated impairment loss		$ 8,700

[1] Gross amount of goodwill for our ILS segment was $340.2 million at October 3, 2020 and $343.3 million at September 28, 2019, respectively. At October 3, 2020 and September 28, 2019, the accumulated impairment loss for the ILS reporting unit was $340.2 million and $13.0 million, respectively, reflecting impairment charges in fiscal 2020 and fiscal 2009.

[2] Gross amount of goodwill for our OLS segment was $110.0 million and $105.5 million at October 3, 2020 and September 28, 2019, respectively. At both October 3, 2020 and September 28, 2019, the accumulated impairment loss for the OLS reporting unit was $8.7 million reflecting impairment charges in fiscal 2003 and fiscal 2009.