Compact Heterodyne Interferometer for High Precision Displacement Measurements

Abstract

The Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Laser Interferometer Space Antenna (LISA) both utilize displacement measuring interferometers to obtain high precision measurements of linear motion. Displacement measuring interferometers are among the most sensitive devices for tracking linear motion. High precision measurements are primarily limited by periodic errors, also known as nonlinear errors, which arise from frequency mixing, polarization mixing, and ghost reflections. These errors can be mitigated by spatially separating the beams in the interferometer and through purposeful misalignment of the optics. It was determined that the compact heterodyne interferometer designed and built through this research shows achievable picometer level displacement sensitivity in air, has no detectable periodic errors, and was found to be twice as thermally stable as other highly stable commercial interferometers, enabling high precision displacement measurements over long distances.