Tunable reflectance of a two-defect-layer cholesteric liquid crystal

In the present paper we consider reflection spectra peculiarities of a cholesteric liquid crystal (CLC) cell with two defect layers. We consider both the isotropic and anisotropic defect cases. The problem is solved by Ambartsumian's modified layer addition and Muller's matrix methods. We investigated the influence of the defect layer thicknesses and location changes in the CLC cell on the defect modes and the photonic band gap. In particular, we considered (in detail) the cases when the defect layers are half-wave or quarter-wave plates. We also investigated the influence of dielectric borders on the reflection spectra. We showed that the subject system possesses the property of structural nonreciprocity, and that the system can work as a tunable filter, a mirror, and a low threshold laser. We also showed that the system can work as a light modulator, or as an optical diode, or as a system for getting linearly polarized light with electrically tunable polarization plane rotation, as well as a device for getting linearly polarized light from nonpolarized light, again with electrically tunable polarization plane rotation.