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Polarization Optics

There are several designs of polarization scramblers (depolarizers) – divided into two main groups:

 

  • Spatial scrambling
  • Temporal scrambling.

 

The temporal scrambling is usually provided by an electro-optic phase modulator suitable for very fast temporal change of beam polarization state. The spatial polarization scrambler is based upon the polarization state variations across the light beam diameter with no temporal change. BBT design concentrates on the spatial polarization scramblers. The simplest version of spatial scrambler is a single wedge scrambler and a double wedge scrambler, where identical wedges are applied. The function is based upon the variable thickness of the wedge across the beam diameter – it varies continuously from the quarter-wave plate to half-wave plate and so on. The polarization state varies across the beam in the sequence: linear – elliptical – circular – elliptical – linear perpendicular to the previous one – and so on. Calomel wedge scrambler converts a polarized beam into a pseudo-random polarized light beam. The term pseudo-random refers to the transmitted beam which doesn’t become unpolarized but the polarization of the beam is randomized instead.