【作者】 孙亚玫；

【导师】 过振；

【作者基本信息】 西安电子科技大学 ， 光学工程， 2010， 硕士

【摘要】 本论文以倍频理论作为理论基础,以高斯光束为光束模型,研究了在倍频激光器中,倍频过程对基频光的模式分布,基频光以及倍频光的光束质量的影响。假定在圆形镜共焦腔中,初始时刻基频光为基模高斯光束,在倍频晶体的二阶非线性效应的影响下,通过倍频晶体的基频光不再是原来的基模高斯光束,为了描述这种过程,引入模式分解的概念:将通过倍频晶体后的基频光在拉盖尔高斯函数空间里展开,并表示为展开系数与基函数的点积和形式。模式的权重为展开系数的归一化形式。在此基础上,研究了腔外倍频,腔内倍频均匀增益,腔内倍频非均匀增益的情况下,前三阶模式的权重。以初始时刻基频光为基模高斯光束为前提,在腔内倍频情况下,基频光来回通过倍频晶体,且基频光受到激光晶体的增益作用,高阶模式权重可以与基模相比较。更多还原

【Abstract】 Based on the frequent-doubling theory of light, Gaussian beam as a beam model, the beam quality affected by the process of frequent-doubling effecting is studied.Assumed that the beam in confocal resonator at initial time is fundamental-mode Gaussian beam, due to the second-order nonlinear effect of frequency doubling crystal, the beam getting through the frequency doubling crystal is not the fundamental-mode Gaussian beam. To describe the process, the modelling method is introduced. It means that make the beam through the frequency doubling crystal expanding in Laguerre-Gauss function space. The weights of modes are the coefficients by normalizing the coefficient of the expansion. The weights of three modes in the events that frequency doubling crystal is outside the resonator, inside the resonator with well-distributed gain, and inside the resonator with nonequilibrium gain distribution are put forward.In the situation of frequency doubling crystal inside the resonator, the fundamental laser beam get though the frequency doubling crystal back and forth, and it would be magnified by laser crystal. In that case, high modes build-up quickly, and the weight of fundamental-mode Gaussian beam can’t dominate over the beam.更多还原