Revenue - Primary Geography Markets (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Disaggregation of Revenue [Line Items]
Total net revenues	$ 21,565	$ 26,299	$ 69,248	$ 73,441
Products Transferred at a Point in Time
Disaggregation of Revenue [Line Items]
Total net revenues	9,941	17,689	35,574	51,269
Products and Services Transferred Over Time
Disaggregation of Revenue [Line Items]
Total net revenues	11,624	8,610	33,674	22,172
United States
Disaggregation of Revenue [Line Items]
Total net revenues	13,843	9,528	37,656	24,573
Asia
Disaggregation of Revenue [Line Items]
Total net revenues	7,536	16,638	31,262	48,330
Europe
Disaggregation of Revenue [Line Items]
Total net revenues	186	133	330	538
TFE
Disaggregation of Revenue [Line Items]
Total net revenues	9,367	17,116	33,925	49,325
TFE | Products Transferred at a Point in Time
Disaggregation of Revenue [Line Items]
Total net revenues	9,367	17,116	33,925	49,325
TFE | United States
Disaggregation of Revenue [Line Items]
Total net revenues	1,764	478	2,596	995
TFE | Asia
Disaggregation of Revenue [Line Items]
Total net revenues	7,536	16,638	31,262	48,330
TFE | Europe
Disaggregation of Revenue [Line Items]
Total net revenues	67		67
Photonics
Disaggregation of Revenue [Line Items]
Total net revenues	12,198	9,183	35,323	24,116
Photonics | Products Transferred at a Point in Time
Disaggregation of Revenue [Line Items]
Total net revenues	574	573	1,649	1,944
Photonics | Products and Services Transferred Over Time
Disaggregation of Revenue [Line Items]
Total net revenues	11,624	8,610	33,674	22,172
Photonics | United States
Disaggregation of Revenue [Line Items]
Total net revenues	12,079	9,050	35,060	23,578
Photonics | Asia
Disaggregation of Revenue [Line Items]
Total net revenues
Photonics | Europe
Disaggregation of Revenue [Line Items]
Total net revenues	$ 119	$ 133	$ 263	$ 538