Description of Business (Revenue by Product) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 33,426	$ 25,482
Concentration risk percentage	100.00%	100.00%
Navigation And Inertial Sensing
Disaggregation of Revenue [Line Items]
Revenue	$ 9,202	$ 10,267
Concentration risk percentage	28.00%	40.00%
Defense Optoelectronics
Disaggregation of Revenue [Line Items]
Revenue	$ 4,434	$ 3,437
Concentration risk percentage	13.00%	13.00%
CA TV Lasers And Transmitters
Disaggregation of Revenue [Line Items]
Revenue	$ 17,315	$ 9,383
Concentration risk percentage	52.00%	37.00%
Chip Devices
Disaggregation of Revenue [Line Items]
Revenue	$ 743	$ 1,555
Concentration risk percentage	2.00%	6.00%
Other
Disaggregation of Revenue [Line Items]
Revenue	$ 1,732	$ 840
Concentration risk percentage	5.00%	4.00%