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