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<sup>2</sup>) 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 ∼8% in 2 h at 145 kW/cm<sup>2</sup> of pump intensity through thermal detuning phase mismatch.
© 2004 Optical Society of America
(190.0190) Nonlinear optics : Nonlinear optics
(190.2620) Nonlinear optics : Harmonic generation and mixing
(190.4360) Nonlinear optics : Nonlinear optics, devices
(190.4400) Nonlinear optics : Nonlinear optics, materials
Zhi M. Liao, Stephen A. Payne, Jay Dawson, Alex Drobshoff, Chris Ebbers, Dee Pennington, and Luke Taylor, "Thermally induced dephasing in periodically poled KTP frequency-doubling crystals," J. Opt. Soc. Am. B 21, 2191-2196 (2004)