Segment and Revenue Information - Revenue by Category (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 158,444	$ 110,128	$ 87,265
Navigation and Inertial Sensing | Aerospace and Defense
Disaggregation of Revenue [Line Items]
Revenue	36,539	38,983	23,203
Defense Optoelectronics | Aerospace and Defense
Disaggregation of Revenue [Line Items]
Revenue	14,299	16,257	9,883
CATV Lasers and Transmitters | Broadband
Disaggregation of Revenue [Line Items]
Revenue	95,255	44,457	41,150
Chip Devices | Broadband
Disaggregation of Revenue [Line Items]
Revenue	3,106	4,873	10,828
Other Optical Products | Broadband
Disaggregation of Revenue [Line Items]
Revenue	$ 9,245	$ 5,558	$ 2,201