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 11p m/H z at 100m H z and as low as 0.6p m/H z above 1p m. The prototype unit is 20m m×20m m×10m m in size and weighs 4.5g, allowing subsequent integration in compact systems.