Arcoptix S.A Switchable Polarization Rotator

Liquid Crystal twisted nematic polarization rotator (TN cell) is very useful when one wants to rotate the orientation of a linear polarization by a fix amount of typically 45° or 90°. When light is traversing LC twisted nematic cell its polarization follows the rotation of the molecules (see figure below). The screens of any laptop computer is based on the same effect (polarization rotator tutorial). In optical systems the polarization is often rotated by quartz retardation plates (l/2 or l/4 plates). Quartz plates shows high quality and good transmission performances especially in the UV region. However such plates present also some disadvantages: They are expensive, functions only for a narrow spectral bandwidth and have a small incidence angle acceptance (field of view less then 2°). The liquid crystal nematic cells have therefore a large acceptance angle, function over a very large spectral range from VIS to NIR (if they are thick enough) and are less expensive. Optionally, by applying a voltage on the TN cell, the polarization rotation can be “switched off”. Also when placing a 90° twisted cell between crossed polarizers it can be used as a shutter. • l/2 plate for a very broadband range of wavelengths • Optionally rotation effect can be electrically switched off • In combination with two crossed polarizers it can be used as an optical shutter