Hysteresis of the temperature phase-matching curve in second harmonic generation

Theoretical and experimental investigations were made of the effect of self-heating of a nonlinear crystal by radiation on second harmonic generation in crystals characterized by dispersion of the linear absorption and by nonlinear (two-stage or two-photon) absorption. It was found that, when the average power of the fundamental-frequency radiation reaches a certain threshold value, hysteresis is observed in the dependence of the second-harmonic power on the temperature of the nonlinear crystal.