Influence of thermal effect on KTP type-II phase-matching second-harmonic generation

By considering the influence of phase mismatching resulting from the therma l effect of KTiOPO4 (KTP), the type-II phase-matching second-harmonic-wave (SHW) power is calculated under the small-signal and the near-field approxi mations. The influences of thermal effect on the SHW intensity profile and the nonlinear conversion efficiency are analyzed in detail. The calculated results show that the thermal effect can result in a more severe reduction in conversion efficiency at high fundamental-wave (FW) power or/and long KT P length for a fixed FW beam width in comparison with the case where only w alking-off effect is considered. It also shows that it is the combined infl uences of thermal effect and walking-off effect of KTP that result in the d istortion of harmonic intensity distribution. (C) 2001 Published by Elsevie r Science B.V.