Systems using polarization-manipulating retroreflectors

Measurement systems that separate polarization components can use retroreflectors to preserve or transform polarization and avoid unwanted mixing of the polarization components. A suitable retroreflector can include a coated cube corner reflector with retardation plates having a slow axis set at a non-zero angle away from 45° with the directions of linearly polarized component beam. The non-zero angle can be set in situ to minimize polarization mixing in a measurement system. Alternatively, a cube corner reflector with one or more polarization manipulating elements controls the polarization of a reflected beam to preserve or transform the polarization of an incident beam.