Quasi-monolithic heterodyne laser interferometer for inertial sensing.

We present a compact heterodyne laser interferometer developed for high-sensitivity displacement sensing applications. This interferometer consists of customized prisms and wave plates 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 / at 100 and as low as 0.6 / above 1 . The prototype unit is 20 ×20 ×10 in size and weighs 4.5, allowing subsequent integration in compact systems.