KDP晶体折射率不均匀性对三倍频转换效率的影响

 采用正交偏振干涉测量法获得了典型的快速(RG)和传统(CG)生长的KDP晶体折射率空间分布，数值模拟了倍频晶体固定失谐角分别为0和220 mrad时晶体折射率不均匀性对高功率三倍频光转换效率的影响。结果表明：快速生长晶体的折射率不均匀性的均方根约为传统生长晶体的6倍；三倍频转换效率在低功率密度下对折射率不均匀性不敏感，在高功率密度下尤其是转换效率较高时很敏感；当混频过程中的二倍频光不过剩时，在晶体折射率变化对三倍频效率的影响方面，倍频晶体比混频晶体严重；目前国产的传统生长晶体可以满足高功率三倍频实验要求。

Influence of KDP crystals' refractive-index non-uniformities on 3ω conversion efficiency

The spatial refractive index distribution of typical rapid-growth(RG) crystals and conventional-growth(CG) crystals were obtained with orthogonal polarization interferometry. By numerical simulation, the influence of crystal refractive-index non-uniformities on 3w conversion efficiency was also conducted for a fixed doubler detuning angle of 0 and 220 mrad respectively. The results show that the RMS refractive index uniformities error of RG crystals is about sixfold compared with that of CG crystals, and 3w conversion efficiency is insensitive to refractive-index non-uniformities when 1w irradiance was low, however, it is sensitive around the inflexion point. The refractive index variation of a doubler contributes more to the degrading of 3w conversion efficiency than that of a tripler, on