Segment Reporting - Information for Each Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 28, 2020	Mar. 30, 2019
Segment Reporting Information [Line Items]
Total segment net revenues	$ 18,840	$ 24,827
Operating income (loss)	(1,100)	(1,999)
Interest income	142	160
Income (loss) before income taxes	(958)	(1,839)
TFE
Segment Reporting Information [Line Items]
Total segment net revenues	7,962	18,945
Photonics
Segment Reporting Information [Line Items]
Total segment net revenues	10,878	5,882
Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	381	(1,243)
Operating Segments | TFE
Segment Reporting Information [Line Items]
Operating income (loss)	(2,531)	(603)
Operating Segments | Photonics
Segment Reporting Information [Line Items]
Operating income (loss)	2,912	(640)
Unallocated Amount to Segment
Segment Reporting Information [Line Items]
Unallocated costs	$ (1,481)	$ (756)