Efficiency of non-phase-matched second-harmonic generation by Gaussian pulses

Conversion efficiency contour plots for second-harmonic generation by optical pulses exhibiting Gaussian temporal and spatial profiles are calculated numerically based on the monochromatic plane-wave theory. Comparison with a similar plot for pump pulses constant in time and space shows that Gaussian pulses convert less efficiently at low nonlinear drives and more efficiently in a specific range of high drives. This effect is due to the intensity-dependent period of conversion. We calculated the harmonic pulse shapes using the suggested computational routine and found them to depend on the magnitude of drive as well. The pulse shape is nearly Gaussian at low drives, but it becomes severely distorted at intermediate and high drives. It is shown that the conversion efficiency contour plots provide a convenient tool for evaluating the trade-off between the desirable efficiency and other parameters of the conversion process in the case of Gaussian pulses. (C) 1997 Optical Society of America.