Information for Each Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 30, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Total segment net revenues	$ 24,827	$ 17,974
Loss from operations	(1,999)	(5,121)
Interest income and other income (expense), net	160	145
Loss before income taxes	(1,839)	(4,976)
TFE
Segment Reporting Information [Line Items]
Total segment net revenues	18,945	12,789
Photonics
Segment Reporting Information [Line Items]
Total segment net revenues	5,882	5,185
Operating Segments
Segment Reporting Information [Line Items]
Loss from operations	(1,243)	(3,719)
Operating Segments | TFE
Segment Reporting Information [Line Items]
Loss from operations	(603)	(2,509)
Operating Segments | Photonics
Segment Reporting Information [Line Items]
Loss from operations	(640)	(1,210)
Unallocated Amount to Segment
Segment Reporting Information [Line Items]
Unallocated costs	$ (756)	$ (1,402)