Photorefractive inhibition of second harmonic generation in periodically poled MgO doped LiNbO₃ waveguide

The inhibition of high power second-harmonic generation (SHG) in a periodically poled MgO doped LiNbO₃ (PPMgLN) waveguide operating at near the room temperature has been interpreted by systematically investigating the SHG process based on the coupled mode equations in combination with the photorefraction and the temperature nonuniformities. The simulation results show that significant refractive index nonuniformities are induced by the photorefractive effect along the irradiated zone while those induced by the thermal effect are very minor. Therefore, the photorefractive effect instead of the thermal effect is the main factor that inhibits the SHG conversion efficiency. In addition, comparison of PPMgLN waveguides with different transverse dimensions shows that the waveguides with larger transverse dimension is advantageous in high power SHG since the photorefractive effect is weaker.