Restructuring Charges (Details) - USD ($)	3 Months Ended						9 Months Ended
	Jul. 04, 2020	Apr. 04, 2020	Dec. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 29, 2018	Jul. 04, 2020	Jun. 29, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring cost relating to HPFL products at Germany facility			$ 20,900,000
Restructuring Reserve [Roll Forward]
Starting balance	$ 4,257,000	$ 7,895,000	8,494,000	$ 747,000	$ 831,000	$ 1,122,000	$ 8,494,000	$ 1,122,000
Provision	518,000	1,079,000	933,000	21,273,000	880,000	476,000
Payments and other	(3,721,000)	(4,717,000)	(1,532,000)	(11,813,000)	(964,000)	(767,000)
Ending balance	1,054,000	4,257,000	7,895,000	10,207,000	747,000	831,000	1,054,000	10,207,000
Restructuring cost incurred	100,000
Restructuring charges relating to accelerated depreciation and consulting	100,000	500,000	600,000
Santa Clara facility combine project related restructuring charge	400,000	600,000	200,000
Industrial Lasers & Systems
Restructuring Reserve [Roll Forward]
Restructuring cost incurred	100,000						1,300,000
OEM Laser Sources
Restructuring Reserve [Roll Forward]
Restructuring cost incurred	400,000						1,200,000	0
Severance Related
Restructuring Reserve [Roll Forward]
Starting balance	4,045,000	7,675,000	8,279,000	682,000	601,000	836,000	8,279,000	836,000
Provision	(77,000)	85,000	54,000	9,338,000	282,000	212,000
Payments and other	(3,136,000)	(3,715,000)	(658,000)	19,000	(201,000)	(447,000)
Ending balance	832,000	4,045,000	7,675,000	10,039,000	682,000	601,000	832,000	10,039,000
Severance Related | Other current liabilities
Restructuring Reserve [Roll Forward]
Ending balance	1,100,000						1,100,000
Asset Write-Offs
Restructuring Reserve [Roll Forward]
Starting balance	0	0	0	0	0	0	0	0
Provision	554,000	915,000	599,000	11,798,000	247,000	76,000
Payments and other	(554,000)	(915,000)	(599,000)	(11,798,000)	(247,000)	(76,000)
Ending balance	0	0	0	0	0	0	0	0
Other
Restructuring Reserve [Roll Forward]
Starting balance	212,000	220,000	215,000	65,000	230,000	286,000	215,000	286,000
Provision	41,000	79,000	280,000	137,000	351,000	188,000
Payments and other	(31,000)	(87,000)	(275,000)	(34,000)	(516,000)	(244,000)
Ending balance	$ 222,000	$ 212,000	$ 220,000	$ 168,000	$ 65,000	$ 230,000	$ 222,000	$ 168,000