Determination of Optimal Directions of the Wave Vector of a Phase Holographic Grating in Cubic Photorefractive Crystal V. N. Naunyka Crystallography Reports, 2023 Abstract The dependence of the change in the components of the inverse permittivity tensor of a cubic photorefractive Bi12SiO20 crystal on the direction of the wave vector of holographic grating in the crystal coordinate system has been studied. It is shown that, when recording a phase hologram, the largest change in the refractive index of Bi12SiO20 crystal is attained when the holographic grating wave vector is oriented along symmetrically equivalent 〈111〉 directions. The maximum possible modulation amplitude of the refractive index of a holographic grating with the wave vector oriented along the 〈110〉 directions is found to exceed that in the case of orientation along the 〈100〉 directions. The components of the inverse permittivity tensor of Bi12SiO20 crystal were calculated taking into account that a phase hologram is recorded under linear electro-optic, photoelastic, and inverse piezoelectric effects.
Four-Wave Mixing by Phase-Amplitude Holographic Gratings in the Photorefractive Piezocrystal of Symmetry Class V. N. Naunyka Optics and Spectroscopy, 2023 A system of coupled-wave equations for calculating the vector amplitudes of linearly polarized light waves at four-wave mixing by phase-amplitude holographic gratings in a cubic photorefractive semiconductor of an arbitrary cut belonging to the $$\bar {4}3m$$ symmetry class is presented. The dependencies of the intensities of the polarization components of the reversed light wave on the orientation angle for GaAs crystal of (110)‑cut are calculated on the basis of the numerical solution of the system of coupled wave equations. The obtained dependences are compared with the known theoretical and experimental data. It is shown that the best agreement between the results of theoretical modeling and experimental data at calculating the contra-directional four-wave mixing in GaAs crystal of (110)-cut is achieved if formation of several phase-amplitude holographic gratings is allowed, and the contribution of the photoelastic and inverse piezoelectric effects are taken into account together with absorption of the crystal.
Effect of Optical Activity on Degenerated Four-Wave Mixing in Cubic Photorefractive Crystal V. N. Naunyka Bulletin of the Russian Academy of Sciences Physics, 2022 A system of coupled waves equations for calculation the vector amplitudes of linearly polarized light waves during their degenerate contra-directional four-wave mixing in cubic photorefractive crystals of 23 and $$\bar {4}3m$$ symmetry classes in general spatial orientation was obtained. Linear electrooptic, photoelastic, and inverse piezoelectric effects, as well as natural optical activity, absorption and circular dichroism are taken into consideration at the theoretical modelling. The dependencies of intensity of p- and s-components of the phase-conjugated wave on the crystal orientation angle and the thickness of one at different polarization azimuths of the signal wave for GaAs and Bi12SiO20 crystals of (110)-cut are analyzed. It is shown that these dependencies for Bi12SiO20 crystal exhibiting optical activity differ from the ones derived for optically non-active GaAs crystal. It takes place since under the combined action of the induced anisotropy and optical activity, the conditions of diffraction of the light waves during their four-wave mixing by holographic gratings formed in the Bi12SiO20 crystal will be different with respect to ones in GaAs. It is established that the effect of optical activity on intensity of the phase-conjugated wave considerably depends on the values of the crystal orientation angle, thickness, and polarization azimuths of the signal wave. Optical activity can lead to both decreasing and increasing of intensity of the phase-conjugated wave in dependence on the conditions of holographic experiment.
Counterpropagating Four-Wave Mixing on Amplitude–Phase Holographic Gratings in a Qubic Photorefractive Crystal V. N. Naunyka Bulletin of the Lebedev Physics Institute, 2022 Abstract A system of coupled wave equations that can be used to find the components of the vector amplitudes of linearly polarized light waves on amplitude–phase holographic gratings formed in a cubic photorefractive crystal due to four-wave mixing has been presented. The linear electro-optical, photoelastic, and inverse piezoelectric effects, as well as natural optical activity, circular dichroism, and absorption in the crystal, have been taken into account when deriving the coupling equations. The characteristics of energy exchange in a (111) InP:Fe crystal in the presence of four-wave mixing have been analyzed. It has been shown that the best agreement of the theoretically calculated dependences of the intensities of the p and s polarized components of the conjugate light wave on the orientation angle with the known experimental results is achieved under the assumption that several amplitude–phase holographic gratings are formed in the crystal. The dependence of the intensity of the conjugate wave on the orientation angle and the azimuth of the linear polarization of the pump wave has been theoretically studied. It has been shown that this intensity can be significantly increased by choosing the optimal values of these parameters.
Energy Exchange at Counterpropagating Two-Wave Mixing in a Bi12GeO20 Crystal of (001) Cut V. N. Naunyka, A. V. Makarevich, V. V. Yuditskii, S. M. Shandarov Technical Physics Letters, 2021 Regularities have been analyzed of energy exchange between two linearly polarized light waves upon their counterpropagating mixing at a volume reflection holographic grating formed in a Bi12GeO20 photorefractive crystal of (001) cut. The crystal thickness and azimuths of linear light polarization at which the object wave is amplified are determined. It is demonstrated experimentally that, depending on the crystal thickness, the energy-exchange direction may reverse.
