Multi-crystal Achromatic Quarter Wave Retarder for the Air-Multiangle Spectropolarimetric Imager (AirMSPI) in SWIR region

Air Multiangle Spectro-Polarimetric Imager (MSPI) is an instrument for multi-angle polarization imagery which is used for the Aerosol-Cloud-Ecosystem (ACE) mission introduced by NASA. It was installed in ER-2 aircraft. The main component of the instrument is an achromatic quarterwave retarder with two photo elastic modulator. In this present communication we propose a four-element multi-crystal (Calcite; Quartz; KDP; Rutile) quarter wave retarder for SWIR range extending from 1000-2300 nm with retardance variation of 90°±1.25°. It is optimized for 1000, 1500, 2000 and 2300 nm.