PHOTOREFRACTIVE AND OPTICAL-PROPERTIES OF CERIUM-DOPED (SRCA)2NANB5O15

The photorefractive effect is demonstrated in a single crystal of ferroelectric Ba-modified Ce-doped (SrCa)2NaNb5O15, for the first time to our knowledge. From two-beam coupling the gain and the time response were found. The maximum intensity gain with ordinary light at a 488-nm wavelength was GAMMA - 10 cm-1, while the photorefractive time response was determined to be 1.85 s at an incident intensity of I = 1 W/cm2. The phase shift of the index gratings from the intensity grating was found to vary with angle from approximately 28-degrees at a 79-degrees crossing angle to 55-degrees at a 13-degrees crossing angle. The dark decay was measured, and the two-beam coupling intensity gain was found to oscillate with time. The oscillation period and the dc component were found to depend on the crossing angle. Beam fanning was observed with a transmitted beam reduction of 1.61 optical density and a time response of tau approximately 5.6 s at I = 230 mW/cm2. Finally, anisotropic conical diffraction was observed in the form of a partial ring pattern about the transmitted (extraordinary-polarized) incident beam in a direction opposite the beam fan. When the dependence of the angle between the ring and the transmitted beam is fitted to the change in the incident angle, it is possible to measure the birefringence, which was n(e) - n(o) = -0.051.