超高斯光束二次谐波转换中的衍射和离散效应

THE DIFFRACTION AND WALKOFF IN THE SECOND HARMONIC GENERATION OF SUPER-GAUSSIAN BEAM

采用ＫＤＰ晶体Ⅰ类匹配的方案，以超高斯光束的二倍频为例，通过求解包含衍射、离 散的非线性耦合波方程，考虑衍射和离散两种因素对二次谐波转换效率的影响并对其作数值 模拟计算．结果表明，衍射的影响非常小．当入射超高斯光束口径较小时，离散效应的存在将 大大降低倍频转换效率．随着入射光束口径的增大，离散效应的影响相应地减小，甚至可以 忽略．

Using the type I matching scheme and taking the second harmoic generation of superGaussian beam in a KDP crystal for example,we have worked out the effects of diffraction and walkoff to doubling conversion efficiency by solving the coupling wave equations of doubling including diffraction and walkoff. The result indicates that the effect of diffration is very small. When the spot size of the input super-Gaussian beam is small,the walkoff is very deleterious to doubling conversion. At the same time,along with the enlarging of beam spot size, the effect of walkoff is smaller,even ignored.