Quasi-monolithic heterodyne laser interferometer for inertial sensing

Abstract

We present a compact heterodyne laser interferometer developed for high-sensitivity displacement sensing applications. This interferometer consists of customized prisms and waveplates assembled as a quasi-monolithic unit to realize a miniaturized system. The interferometer design adopts a common-mode rejection scheme to provide a high rejection ratio to common environmental noise. Experimental tests in vacuum show a displacement sensitivity level of 11 pm/ √ Hz at 100 mHz, and as low as 0.6 pm/ √ Hz above 1 Hz. The prototype unit has the size of 20 mm × 20 mm × 10 mm and weighs 4.5 g, which allows subsequent integration into compact systems.