Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Apr. 03, 2021	Jan. 02, 2021	Apr. 04, 2020	Dec. 28, 2019	Apr. 03, 2021	Apr. 04, 2020
Restructuring Reserve [Roll Forward]
Starting balance	$ 3,879	$ 2,841	$ 7,895	$ 8,494	$ 2,841	$ 8,494
Provision	3,658	5,383	1,079	933
Payments and other	(3,213)	(4,345)	(4,717)	(1,532)
Ending balance	4,324	3,879	4,257	7,895	4,324	4,257
Restructuring cost incurred				100
Restructuring charges relating to accelerated depreciation and consulting			500	600
Santa Clara facility combine project related restructuring charge	100		600	200
Industrial Lasers & Systems
Restructuring Reserve [Roll Forward]
Restructuring cost incurred		3,600		600	8,900	1,300
OEM Laser Sources
Restructuring Reserve [Roll Forward]
Restructuring cost incurred	100			500	100	700
Severance Related
Restructuring Reserve [Roll Forward]
Starting balance	2,875	2,611	7,675	8,279	2,611	8,279
Provision	2,775	819	85	54
Payments and other	(2,032)	(555)	(3,715)	(658)
Ending balance	3,618	2,875	4,045	7,675	3,618	4,045
Severance Related | Other current liabilities
Restructuring Reserve [Roll Forward]
Ending balance	4,300				4,300
Asset Write-Offs
Restructuring Reserve [Roll Forward]
Starting balance	0	0	0	0	0	0
Provision	558	3,509	915	599
Payments and other	(558)	(3,509)	(915)	(599)
Ending balance	0	0	0	0	0	0
Other
Restructuring Reserve [Roll Forward]
Starting balance	1,004	230	220	215	230	215
Provision	325	1,055	79	280
Payments and other	(623)	(281)	(87)	(275)
Ending balance	706	1,004	$ 212	$ 220	$ 706	$ 212
Write-offs of Excess Inventory and Accruals for Vendor Commitments
Restructuring Reserve [Roll Forward]
Restructuring cost incurred	$ 3,600	$ 5,400