Influence of phase mismatching on temporal waveform of pulse in the process of frequency conversion

Abstract

The influence of phase mismatching on output pulse temporal waveform in the process of second and third harmonic generation at various power densities with different detuning angles is studied based on nonlinear coupled-wave equations. The rules of different frequencies pulse width vary with the detuning angle have been analyzed quantitatively in potassium dihydrogen phosphate (KDP) crystals. The results of numerical simulation show that in high power laser frequency conversion system, the changes of fundamental pulse width are more sensitive to the detuning angle than second harmonic in the process of doubling, and the maximum variation of the full-width at half-maximum (FWHM) of fundamental at different detuning angles is about 19.0%. For tripling, the output pulse width changes of fundamental and second harmonic are sensitive to the detuning angle at high power density, and the maximum variation of their FWHM at different detuning angles are about 19.0% and 19.2%, respectively. However, the SH pulse width almost unchanged at low power density. The results of this study may provide a promising route to determine the best angle for phase matching in the angle adjusting process of experiment.