Experimental evidence of the bulk photovoltaic effect in photorefractive K1-xLixTa1-xNbyO3 (KLTN) crystals is shown. The dependence of the bulk photovoltaic effect on the pbotorefractive impurities type is presented. The current voltage characteristic is presented for different temperatures. It was found that, in Fe-doped KLTN crystals at low temperature, the bulk photovoltaic effect is the dominant transport mechanism contributing to the photorefractive process.
We report here on the fabrication and optimization of composites of conjugated polymer in Sol-Gel and PVA matrices. FTIR spectroscopy as well as other observations show that efficient phase and absorption holograms can be created in the material upon illumination, via the photochromic effect. The main contribution to the absorption change is chain scission and photo-oxidation mechanism. Optimized holographic composites with diffraction efficiencies as high as 26% are shown. Beam interaction between the writing beams is observed for these composites, while the diffraction efficiencies was improved by an order of magnitude.
We report the first observation of self-modified optical diffraction, beam ellipticity recovery and conservation, and intensity independent self-focusing in an anisotropic diffusion-type nonlinearity realized in ferroelectrics heated above the centrosymmetric transition. The interaction, a photorefractive diffusion-driven quadratic nonlinearity, constitutes the first known natural realization of a higher-order logarithmic nonlinearity and allows an analytical description of the observed phenomena and the prediction of a class of noncircular solitons with no characteristic length scale.
We report on the observation of a new mechanism for self-trapping of optical beams: self-trapping that stems from spontaneous creation of ferroelectric crystalline clusters, seeded by a weak photorefractive diffusion field. This is an evident observation of the highly nonlinear aspects of propagation in a thermodynamically metastable system, including optically driven crystalline ordering in a medium undergoing a phase transition.
