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Diffraction property of volume grating in Ce:KNSBN with differently polarized reading beam

The diffraction efficiency of volume grating written by two- wave mixing in Ce:KNSBN photorefractive crystal as a function of the writing beam ratio for different polarized reading beam is experimentally studied. It is found that, the polarization and the incident direction of the reading beam strongly affect the diffraction efficiency. In the selected direction, the extraordinarily polarized reading beam obtains enhanced diffraction and achieves nearly fifteen times larger diffraction efficiency than the ordinarily polarized reading beam. The modified coupled-wave theory is used to fit the experimental data and the fitting result are coincident with the experimental result. We also theoretically examined the realization between the diffraction efficiency and the amplitude coupling constant k of the reading beam and its diffracted beam. As k < 6cm-1, the diffraction efficiency has single maximum and the maximum diffraction efficiency increases as k increases. As k > 6cm-1, the diffraction efficiency curves exhibit two peaks. But the central position of the curves does not change with the variation of k.