含时电离对分子动态双光子吸收截面的影响  

Effect of Time-Dependent Ionization on Dynamical Two-Photon Absorption Cross Sections of Molecular Media

作　　者：孙玉萍[1] 刘纪彩[1] 王传奎[1] 

机构地区：[1]山东师范大学物理与电子科学学院,山东济南250014

出　　处：《光学学报》2009年第6期1621-1625,共5页Acta Optica Sinica

基　　金：国家973计划(2006CB806000);山东省自然科学基金(Z2007A02)资助课题

摘　　要：通过采用时域有限差分法和预估矫正法数值求解麦克斯韦-布洛赫方程,研究了含时电离对分子材料4,4-二甲氨基二苯乙烯的动态双光子吸收截面的影响。研究结果表明,对周期量级的飞秒脉冲,介质发生的主要是一步共振双光子吸收,入射光强较高时出现双光子吸收饱和现象,入射光强小于双光子吸收饱和光强时介质的双光子吸收截面随入射光强的增大线性减小。在不同的传播距离处,分子的双光子吸收截而有较大的差别,因此,在对不同的实验条件下测得的双光子吸收截而数值进行比较时,需要考虑样品厚度对实验结果的影响。在同一传播距离处,随光电离截面取值的增大介质的双光子吸收截面减小。利用飞秒脉冲测量分子的双光子吸收截面时,通过数值模拟,讨论了已有解析结果的适用条件。The effect of time-dependent ionization on two-photon absorption （TPA） cross section of 4, 4′-bis （dimethylamino） stilbene molecules is studied, through solving, the Maxwell-Bloch equations using an iterative predictor-corrector and finite-difference time-domain technique. The numerical results show that for a few-cycle femtosecond pulse, the one-step resonant TPA is dominating. The two-photon saturation absorption can be observed. The dynamical TPA cross section is a linearly decreasing function of the input pulse intensity when the input intensity is lower than TPA saturation intensity. TPA cross-section of the medium reduces as the value of photoionization cross section increases at the same propagation distance. The propagation distance has an obvious influence on the TPA cross section. The thickness of the molecular samples thus should be taken into account as measuring the TPA cross section. When the femtosecond pulse is applied to measuring the TPA cross section, conditions for the available analytic expressions are discussed.

关 键 词：非线性光学 含时电离 双光子吸收截面 4  4′-二甲氨基二苯乙烯 麦克斯韦-布洛赫方程 

分 类 号：O437.1[机械工程—光学工程]