Revenue - Primary Geography Markets (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 03, 2021	Jun. 27, 2020	Jul. 03, 2021	Jun. 27, 2020
Disaggregation of Revenue [Line Items]
Total net revenues	$ 13,813	$ 28,842	$ 30,054	$ 47,682
Products Transferred at a Point in Time
Disaggregation of Revenue [Line Items]
Total net revenues	5,643	17,240	15,252	25,632
Products and Services Transferred Over Time
Disaggregation of Revenue [Line Items]
Total net revenues	8,170	11,602	14,802	22,050
United States
Disaggregation of Revenue [Line Items]
Total net revenues	10,492	12,438	17,819	23,813
Asia
Disaggregation of Revenue [Line Items]
Total net revenues	3,248	16,282	8,269	23,725
Europe
Disaggregation of Revenue [Line Items]
Total net revenues	73	122	3,966	144
TFE
Disaggregation of Revenue [Line Items]
Total net revenues	5,369	16,595	14,607	24,557
TFE | Products Transferred at a Point in Time
Disaggregation of Revenue [Line Items]
Total net revenues	5,369	16,595	14,607	24,557
TFE | Products and Services Transferred Over Time
Disaggregation of Revenue [Line Items]
Total net revenues	0	0	0	0
TFE | United States
Disaggregation of Revenue [Line Items]
Total net revenues	2,121	313	2,488	832
TFE | Asia
Disaggregation of Revenue [Line Items]
Total net revenues	3,248	16,282	8,269	23,725
TFE | Europe
Disaggregation of Revenue [Line Items]
Total net revenues	0	0	3,850	0
Photonics
Disaggregation of Revenue [Line Items]
Total net revenues	8,444	12,247	15,447	23,125
Photonics | Products Transferred at a Point in Time
Disaggregation of Revenue [Line Items]
Total net revenues	274	645	645	1,075
Photonics | Products and Services Transferred Over Time
Disaggregation of Revenue [Line Items]
Total net revenues	8,170	11,602	14,802	22,050
Photonics | United States
Disaggregation of Revenue [Line Items]
Total net revenues	8,371	12,125	15,331	22,981
Photonics | Asia
Disaggregation of Revenue [Line Items]
Total net revenues	0	0	0	0
Photonics | Europe
Disaggregation of Revenue [Line Items]
Total net revenues	$ 73	$ 122	$ 116	$ 144