Non-stationary vectorial two-wave interaction in a cubic gyrotropic photorefractive crystal with an applied electric field

An exact analytical description of non-stationary vectorial two-wave interaction in a cubic gyrotropic photorefractive crystal with an applied constant or square-wave electric field is presented for the case of small modulation index of the interference light pattern in the quasi-static approximation with respect to electrons photoexcited from a single donor level. The influence of the self-diffraction of light waves on the temporal dynamics of the space-charge field is analyzed in the wide frequency range of an external square-wave electric field. Increasing attention is being focused on the comparison of two-wave coupling at two opposite interaction orientations, which are obtained from each other by the rotation of a crystal through 180° about the normal to the entrance face. The non-mutuality of amplification and attenuation of the intensity of a weak light wave is demonstrated during two-wave interaction in a Bi12TiO20 crystal with an applied square-wave electric field of approximately 10 kV/cm. The possibility of non-unidirectional energy exchange on the local component of the photorefractive grating is shown for high applied-field frequencies, when the interaction is steady state during the entire temporal period, and for the steady state at low frequencies.