Revenue Recognition Disaggregation of revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Jan. 02, 2021	Dec. 28, 2019
Disaggregation of Revenue [Line Items]
Net sales	$ 326,053	$ 320,771
OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	211,162	200,948
Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	114,891	119,823
Products | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	125,577	109,836
Products | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	89,312	93,903
Other products and services revenues | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	85,585	91,112
Other products and services revenues | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	25,579	25,920
Sales of spare parts
Disaggregation of Revenue [Line Items]
Net sales	16,000	14,400
Microelectronics | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	128,173	114,893
Microelectronics | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	20,675	15,653
Precision manufacturing | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	11,859	10,395
Precision manufacturing | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	69,591	77,977
Instrumentation | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	67,276	68,186
Instrumentation | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	17,951	18,994
Aerospace and defense | OEM Laser Sources
Disaggregation of Revenue [Line Items]
Net sales	3,854	7,474
Aerospace and defense | Industrial Lasers & Systems
Disaggregation of Revenue [Line Items]
Net sales	$ 6,674	$ 7,199