Photorefractive beam coupling between orthogonally polarized light beams by linear dichroism in Cu-doped potassium sodium strontium barium niobate

Abstract

Two-beam coupling between orthogonally polarized waves is demonstrated by use of linear dichroism in Cu-doped potassium sodium strontium barium niobate. A maximum coupling gain coefficient of approximately 4 cm-1 is obtained at a grating spacing of 1 µm and a wavelength of 514.5 nm, where linear dichroism is moderate. The experimental results are compared with a theoretical model that allows a photorefractive grating to have an arbitrary phase shift with respect to an intensity-interference pattern. Fitting results indicate that the grating is not 90°-phase-shifted under open-circuit conditions. The contribution of the bulk photovoltaic field to the photorefractive phase shift is discussed.