High-Intensity Laser Frequency Doubling in KDP with a Temperature Distribution

Research on the high-intensity laser frequency doubling in KDP crystal with a temperature distribution for typeIangle-phase matching has been carried out by the use of a split-step fast Fourier transform algorithm and a fourth-order Runge-Kutta(R-K) integrator method. Special attention has been paid on the influences of the temperature distribution in the crystal owing to laser energy´s absorption upon the conversion. The rules of the output beam´s distribution, the frequency conversion efficiency and M² factor versus the crystal´s temperature distribution have been analyzed quantitatively. Results indicate that the crystal´s temperature distribution-a self-induced thermal effect, behaves in the way that it causes the thermal induced refractive index variation and then the phase mismatching for fundamental wave and harmonic wave, finally it leads to the variation of the output beams, the decrease of the conversion efficiency and the degradation of the harmonic beam quality.