Dynamics of second-harmonic generation in a photovoltaic photorefractive quadratic medium

摘要

We investigate second-harmonic generation (SHG) in a photorefractive photovoltaic medium such as lithiumnniobate. Our numerical model reveals the complex dynamics of the parametric process during the buildup ofnthe index modification due to the photorefractive (PR) nonlinearity. We investigate a condition in which nonexternal field is applied to the crystal, resulting in a defocusing nonlinearity, as well as the case in which annexternal bias is applied, producing a self-focusing effect that can enhance the conversion efficiency of the parametricnprocess. We also find the conditions for the initial phase matching and for the background illuminationnleading to a stable self-confined propagation of the second-harmonic generated light. The developed numericalnmodel shows that as a general case SHG in a self-focusing PR medium results in mode beating inside the generatednwaveguide, as experimentally observed. © 2009 Optical Society of America