多色、多频光谱角色散匀滑技术的参数优化

Parameters Optimization for Multi-color Multi-central Frequency Smoothing by Spectral Dispersion

针对多色、多频光谱角色散束匀滑方案,数值模拟和分析了多色波长差、多频波长差、带宽和色循环数等主要参数对远场光场均匀性的影响,进而对相关参数进行了优化。结果表明,随着多色波长差的增加,远场焦斑均匀性呈先变好后降低的趋势,即存在最佳波长差;当多频波长差和带宽增加时,远场光场均匀性均得到改善,但考虑高效三倍频的影响,多频波长差和带宽均不宜取太大。当光栅色散系数不变时,远场光强对比度随色循环数的增大呈先减小后增大的趋势,即存在最佳色循环数的选择问题,但最佳色循环数并不为1,而是随着光源参数和光栅参数的变化而有所变化。

Focused on the scheme of the multi- color and multi- central frequency smoothing by spectral dispersion, the effects of the main parameters on the target uniformity are numerically simulated and analyzed, including the multi-color wavelength difference, the multi-central frequency wavelength difference, the bandwidth and the number of color cycle. And then, the parameters are further optimized. The results show that the target uniformity is first improved and then degraded with the increase of the multi-color wavelength difference, which means that there is an optimized multi-color wavelength difference. When the multi-central frequency wavelength difference and the bandwidth increase, the target uniformity is improved. However, neither of these two parameters could be too large since they are limited by the high efficiency of the third harmonic generation. For the given grating dispersion, the contrast of far field first decreases and then increases with the increase of the color cycle number. Therefore, the optimization is required under further analysis. The preliminary analysis indicates that the best color cycle number is not just to be one any more and changes with the parameters of the laser source and the grating.