Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended
	Jan. 02, 2021	Dec. 28, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring charges relating to accelerated depreciation and consulting		$ 600
Restructuring Reserve [Roll Forward]
Starting balance	$ 2,841	8,494
Restructuring Reserve, Period Increase (Decrease)	5,383	933
Restructuring related payment and other during the period	(4,345)	(1,532)
Ending balance	3,879	7,895
Restructuring cost incurred		100
Santa Clara facility combine project related restructuring charge		200
Industrial Lasers & Systems
Restructuring Reserve [Roll Forward]
Restructuring cost incurred	5,400	700
OEM Laser Sources
Restructuring Reserve [Roll Forward]
Restructuring cost incurred		200
Severance Related
Restructuring Reserve [Roll Forward]
Starting balance	2,611	8,279
Restructuring Reserve, Period Increase (Decrease)	819	54
Restructuring related payment and other during the period	(555)	(658)
Ending balance	2,875	7,675
Severance Related | Other current liabilities
Restructuring Reserve [Roll Forward]
Ending balance	3,900
Asset Write-Offs
Restructuring Reserve [Roll Forward]
Starting balance	0	0
Restructuring Reserve, Period Increase (Decrease)	3,509	599
Restructuring related payment and other during the period	(3,509)	(599)
Ending balance	0	0
Other
Restructuring Reserve [Roll Forward]
Starting balance	230	215
Restructuring Reserve, Period Increase (Decrease)	1,055	280
Restructuring related payment and other during the period	(281)	(275)
Ending balance	1,004	$ 220
Write-offs of Excess Inventory and Accruals for Vendor Commitments
Restructuring Reserve [Roll Forward]
Restructuring cost incurred	$ 5,400