波前场曲对激光诱导液晶远场衍射环的影响

摘要

为了明确入射激光参量对激光诱导衍射环的影响及其机理,利用菲涅耳-基尔霍夫衍射积分公式,数值模拟研究了高斯光束波前场曲对于高斯光束通过自散焦液晶介质后远场衍射图样的影响.结果表明,当波前场曲为无穷大时,随着光强的逐渐增大,远场衍射光斑中心明暗交替变化;当波前场曲为正时,随着波前场曲的减小,远场衍射光斑中心强度逐渐变暗并且平滑;当波前场曲为负时,随着波前场曲绝对值的减小,远场衍射光斑中心光强逐渐变强,且中心衍射亮斑较细锐.利用基尔霍夫衍射积分公式中的振幅因子和相位因子对这种现象进行了阐述,这对理解波前场曲与非线性相位因子的相互作用机制是有帮助的.%To elucidate the effect of field curvature on laser-induced far-field diffraction and its mechanism, the effect of field curvature on the far-field diffraction ring pattern after Gaussian beam propngating through self-defocusing liquid crystal was simulated based on Kirchhoff diffraction integral.Without considering the filed curvature effect, the central spot of the far-field diffraction ring will turn out to be bright and dark alternatively with the incident laser intensity increasing.With divergent beam traversing thin self-defocusing medium, the central spot will turn out to be darkened, while brightened with the convergent case.Finally the phenomena were explained based on the amplitude and phase factors in the integral expression of Kirchhoff diffraction.The phenomena are attributed to the interaction between the wave-curvature and the nonlinear phase factor.