Photovoltaic laser beam degradation in lithium niobate planar waveguides: two-center model approach

Abstract

Photovoltaic laser beam degradation in lithium niobate (LiNbO 3 ) has been investigated through a finite-differences beam propagation method for nonlinear media. The simulations use a two-center model (Fe 2 ↔Fe 3 , Nb 4Li ↔Nb 5 Li ) that has been recently proved to be necessary to successfully describe the photorefractive effect in nominally pure LiNbO 3 . Refractive index profiles and intensity and phase beam profiles have been calculated for a wide intensity range and several material distances. A good agreement is obtained on comparing simulations and experimental data. This includes self-defocusing for moderate intensities and the complex beam profile structures appearing for high intensities, providing a complete description of this nonlinear optical phenomenon.