Thermal dephasing of quasi-phase-matched second-harmonic generation in periodically poled stoichiometric LiTaO3 at high input power

Abstract

Thermal dephasing was observed in a periodically poled stoichiometric LiTaO3 crystal during second-harmonic generation at high input power. The dephasing was computationally analyzed using a thermo-optical model consisting of a coupled second harmonic process with absorption and a related temperature distribution. The computational results show a coupled spatio-temporal nanosecond pulse evolution of the fundamental and the second harmonic energy with associated temperature fields, leading to thermal dephasing and inhibition of second-harmonic generation at 1064 rim. The onset of strong non-uniform heat generation and a temperature distribution along the direction of propagation of laser beam take place, depending on the input power, due to linear and nonlinear absorption. A practical temperature adjustment is suggested to compensate the non-uniform thermal distribution and to enhance the conversion efficiency at high input powers.