Achromatic angle-insensitive infrared quarter-wave retarder based on total internal reflection at the Si-SiO2 interface

An achromatic infrared (lambda = 1.2-4 microm), Si-prism quarter-wave retarder (QWR) is described that uses total internal reflection at a buried Si-SiO2 interface at an angle of incidence phi near 33 degrees, where deltaDelta/deltaphi = 0. The retardance delta deviates from 90 degrees by < +/- 2 degrees within a field of view of +/- 10 degrees (in air) over the entire bandwidth. Because the SiO2 layer at the base of the prism is optically thick, this QWR is unaffected by environmental contamination.