Double-pass polarization diversified birefringent filter

摘要

A double-pass birefringent filter apparatus comprises an external-interface apparatus (illustratively including of a beam-displacer element and a waveplate element); a birefringent filter comprised of a series of several birefringent waveplates; and a wrap-around unit (illustratively comprised of a beam-displacer element and a retro-reflector). In response to an input beam received at the external-interface apparatus, the double-pass birefringent filter forms two output beams having complimentary intensities which vary periodically with frequency.