Diffraction reflection of light in a cholesteric liquid crystal in the presence of wave irreversibility and bragg formula for media with nonidentical forward and return wavelengths

An analysis is made of the diffraction reflection of light in a cholesteric liquid crystal in the presence of magnetooptic activity which leads to wave irreversibility and in particular to nonidentical forward and return wavelengths. It is shown that in this particular case, the Bragg formula containing a single wavelength which is the same for the forward and return waves should be written to include two wavelengths. Relations are put forward which generalize the Bragg formula for media with nonidentical forward and return wavelengths and examples of using these relations are considered. A boundary-value problem is solved for a layer of cholesteric liquid crystal. (C) 2000 MAIK "Nauka/Interperiodica".