Thermally induced dephasing in periodically poled KTP frequency-doubling crystals

A thermally induced spatial and temporal dephasing model of second-harmonic generation has been developed to describe the conversion efficiency and its degradation of periodically poled potassium titanium phosphate (PPKTP) in a cw, single-pass frequency conversion system. The model confirms the experimental data that show that second-harmonic power greater than 800 mW (15 kW/cm(2)) causes two-photon nonlinear absorption, leading to time-dependent photochromic damage in PPKTP. This added absorption degrades the conversion efficiency from an initial value of 19% to an unrecoverable asymptotic value of similar to8% in 2 h at 145 kW/cm(2) of pump intensity through thermal detuning phase mismatch. (C) 2004 Optical Society of America.