Goodwill and Intangible Assets - Goodwill (Details) $ in Thousands	3 Months Ended
	Dec. 30, 2017 USD ($)
Goodwill [Roll Forward]
Goodwill, beginning of period	$ 417,694
Translation adjustments and other	386
Goodwill, end of period	418,080
OEM Laser Sources
Goodwill [Roll Forward]
Goodwill, beginning of period	102,178
Translation adjustments and other	235
Goodwill, end of period	102,413
Industrial Lasers & Systems
Goodwill [Roll Forward]
Goodwill, beginning of period	315,516
Translation adjustments and other	151
Goodwill, end of period	$ 315,667