Photorefractive effect in annealed proton-exchanged LiNbO₃ waveguides

We compare the photorefractive effect in proton-exchanged (PE) and annealed proton-exchanged (APE) LiNbO₃ optical waveguides at the irradiation wavelength of 488 nm. We measure the intensity dependence of the saturated index change, the build-up time constant, and the photorefractive sensitivity in PE and APE waveguides. In APE waveguides the photorefractive sensitivity is about three times that of PE waveguides up to an irradiation intensity of 100 W/cm². The contribution of the dark conductivity to the photorefractive effect in PE and APE waveguides is found to be dominant in the intensity range used in our experiments.