飞秒激光脉冲倍频特性的数值模拟

Numerical simulation of frequency doubling of femtosecond pulses

模拟了随着传播长度的增加,基频和倍频激光脉冲的时域波形和光谱特性的演变过程。通过引入走离长度和非线性长度,给出了走离效应、群速度色散和三阶非线性效应对飞秒脉冲倍频的影响。研究了飞秒脉冲倍频的波长调谐特性,发现40 ps基频脉冲波长调谐带宽仅有2.8 nm,而40 fs基频脉冲的倍频波长调谐带宽高达42 nm。这在周期极化倍频晶体工艺中有重要应用价值。

The temporal and spectral evolutions of the fundamental and second harmonic （SH） pulses were simulated in the propagation. By introducing the walk-off length and nonlinear length, the walk-off effect, group-velocity dispersion and cubic nonlinearity were described. The wavelength tuning characteristics of femtosecond-pulse second harmonic generation （SHG） were aaalyzed. It was found that the full width at half maximum （FWHM） of the SHG wavelength tuning curve of 40 fs pump pulses can reach as wide as 42 nm, while that of 40 ps pump pulses is only 2.8 nm.