Segment Information - Summary of Revenue by Product Type (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Product Information [Line Items]
Revenue	$ 8,036	$ 11,115	$ 36,773	$ 29,977
Core [Member]
Product Information [Line Items]
Revenue	4,183	7,111	25,111	14,077
Wafer [Member]
Product Information [Line Items]
Revenue	2,085	2,083	6,093	11,472
Optical [Member]
Product Information [Line Items]
Revenue	1,612	1,039	5,016	3,337
Research & Development [Member]
Product Information [Line Items]
Revenue	$ 156	$ 882	$ 553	$ 1,091