Determination of Material Parameters of Photorefractive Crystals Using Adaptive Holographic Interferometry

Optics and Spectroscopy - Holographic interferometry methods, based on mixing of a stationary reference light beam and a phase-modulated signal beam at the related perturbations of the dielectric...     

Observation of the Photoinduced Conductivity in a Regular Domain Structure with Tilted Walls in MgO:LiNbO3 at a Wavelength of 632.8 nm at Bragg Diffraction

A 632.8-nm radiation-induced change in the conductivity of a regular domain structure (RDS) formed in a 5% MgO:LiNbO₃ crystal has been detected for the first time. As a result, the relaxation rate for the Bragg diffraction efficiency on the RDS, which is observed after the application of an external electric field, increases with the intensity of a probe beam. This dependence is linear in the initial stage of relaxation caused by the screening of the external field because of the redistribution of charges over tilted conductive domain walls of the RDS. For the probe beam with an intensity of 49 mW/mm², the induced effective conductivity of the RDS, which is estimated as σ_eff = 3.5×10⁻⁹Ω⁻¹m⁻¹, is more than four orders of magnitude higher than the dark conductivity of the single-domain MgO:LiNbO₃ sample.

     

Effect of incoherent illumination on two-beam interaction of light waves in a bismuth titanate crystal

Experimental investigations and theoretical analysis of the effect of external illumination on the dynamics of formation of photorefractive reflection gratings in a (100)-cut bismuth titanate crystal showed that, in the case of counter interaction of laser beams with a wavelength of 633 nm, incoherent green light may cause a change in the sign of the two-beam gain.     

Structure of elastic and electric fields induced near the boundary of a LiNbO3 crystal in the course of recording of photorefractive gratings through the photovoltaic mechanism

This paper reports on the results of the investigation into the structure of elastic and electric fields induced near the boundary of the X cut of a lithium niobate crystal during the formation of a photorefractive grating with a wave vector K parallel to the threefold symmetry axis due to the photovoltaic effect. The elastic and electric fields induced by the photorefractive grating and the changes in the components of the dielectric impermeability tensor of the lithium niobate crystal at the frequency of the light wave are calculated using numerical analysis. It is demonstrated that light waves with orthogonal polarizations can effectively interact at a photorefractive grating formed near the electrically short-circuited boundary of a lithium niobate crystal.     

Periodic domain structures formed under electron-beam irradiation in LiNbO3 plates and Ti:LiNbO3 planar waveguides of the Y cut

Regular domain structures on the Y cuts of the LiNbO₃ substrates and Ti:LiNbO₃ waveguide structures based on these substrates have been fabricated under electron-beam irradiation. It has been revealed that the domains in undoped and titanium-doped LiNbO₃ crystals are formed as a result of different processes. It has been demonstrated using chemical etching and waveguide second-harmonic generation that regular domain structures in the Ti:LiNbO₃ waveguides are formed at a depth of approximately 8 μm from the surface, where the titanium concentration does not exceed 2 mol %. The quasi-synchronous waveguide optical second harmonic generation with an efficiency of 8.8% has been obtained using the fabricated structures.     

Two-wave mixing on reflection dynamic gratings in sillenite crystals under phase modulation of signal beam

The counter mixing of a strong circularly polarized wave of optical pump with a weak phase-modulated signal wave on the reflection grating formed by them in (111)-, (110)-, and (100)-cut Bi₁₂TiO₂₀ and Bi₁₂SiO₂₀ phototrefractive crystals was theoretically and experimentally studied.     

Structure of the photorefraction lattice near the face of a crystal with 3m symmetry

This article examines the structure of nonuniform elastic and electric fields created near free and electrically shorted faces of a crystal with 3m symmetry during the recording of photorefraction lattices. It is shown that a change in the electrical boundary conditions leads to a significant transformation of the fields of the lattice near the faces. Tomsk State Academy of Control Systems and Electronics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 75–79, September, 1997.     

Electric and magnetic field structures of transverse piezoactive surface acoustic waves in crystal symmetry classes\bar 43m, 23

Institute of Automated Control Systems and Radioelectronics, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 3, pp. 362–368, March, 1989.     

Polarization effects at two-beam interaction on reflection holographic gratings in sillenite crystals

The polarization structure of the signal wave that interacts with a circularly polarized pump wave on the reflection holographic gratings in the (112)-, (111)-, and (110)-cut Bi₁₂TiO₂₀ (BTO) crystals is experimentally and theoretically analyzed. An analytical expression for the vector field of the signal wave that is valid for an arbitrary orientation of the cubic refractive crystal is derived using approximation of the nondepleting circularly polarized pump wave. The contribution of the absorption component of the reflection hologram into the counter interaction is estimated for the crystals under study using the approximation of the experimental data with theoretical curves. Based on the experiments with incoherent quasi-monochromatic radiation, it is demonstrated that the real BTO crystals exhibit weak induced linear birefringence.