Segment Reporting - Information for Each Reportable Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 03, 2021	Jun. 27, 2020	Jul. 03, 2021	Jun. 27, 2020
Segment Reporting Information [Line Items]
Total segment net revenues	$ 13,813	$ 28,842	$ 30,054	$ 47,682
Income (loss) from operations	(6,311)	2,104	(12,812)	1,005
Interest income and other income (expense), net	20	62	50	204
Income (loss) before provision for (benefit from) income taxes	(6,291)	2,166	(12,762)	1,209
TFE
Segment Reporting Information [Line Items]
Total segment net revenues	5,369	16,595	14,607	24,557
Photonics
Segment Reporting Information [Line Items]
Total segment net revenues	8,444	12,247	15,447	23,125
Operating Segments
Segment Reporting Information [Line Items]
Income (loss) from operations	(4,560)	3,362	(9,707)	3,743
Operating Segments | TFE
Segment Reporting Information [Line Items]
Income (loss) from operations	(4,305)	(174)	(8,306)	(2,705)
Operating Segments | Photonics
Segment Reporting Information [Line Items]
Income (loss) from operations	(255)	3,536	(1,401)	6,448
Unallocated Amount to Segment
Segment Reporting Information [Line Items]
Unallocated costs	$ (1,751)	$ (1,258)	$ (3,105)	$ (2,738)