Optical, mechanical and electronic design and integration of POMM, a polarimeter for the Observatoire du mont Mégantic

A polarimeter, to observe exoplanets in the visible and infrared, was built for the “Observatoire du Mont Megantic” (OMM) to replace an existing instrument and reach 10 -6 precision, a factor 100 improvement. The optical and mechanical designs are presented, with techniques used to precisely align the optical components and rotation axes to achieve the targeted precision. A photo-elastic modulator (PEM) and a lock-in amplifier are used to measure the polarization. The typical signal is a high DC superimposed to a very faint sinusoidal oscillation. Custom electronics was developed to measure the AC and DC amplitudes, and characterization results are presented.