Liquid-crystal modulator operating at 10.6 μ

Tunable retarder made of pentaprisms and liquid crystal

“…Even refractive index spectra of materials are difficult to evaluate because of this inconvenience, although birefringence ǻn can be measured with a relatively simple optical setup [121][122][123][124][125][126]. In spite of these difficulties some LC devices have been developed for the mid-infrared region; e.g., infrared modulators that use the scattering-to-transparent phase transition [39][40][41]127], a polarization switch that uses anisotropic total reflection [28], a retardation plate for CO 2 laser [75], and a phased-array for laser beam steering [79].…”

“…If a dimension of an index distribution is smaller than optical wavelength, strong scattering takes place (Rayleigh or Mie scattering). Index distributions can be created in either LC layers, e.g., the cholesteric phase or the dynamic scattering mode [39][40][41], or guest-host composites in which refractive-index mismatch takes place between a guest LC and a host material [42][43][44][45]. When LC molecules are directed suitably by electric-field application, the index distribution disappears and consequently, the LC layer or the composite becomes transparent.…”