末端基团对芴类衍生物分子非线性光学性质的影响

Influence of Terminal Group on Nonlinear Optical Properties of Fluorene Derivatives

通过采用预估矫正的时域有限差分方法数值求解速率方程-光场强度方程,研究了纳秒激光脉冲在具有不同末端基团的对称性芴类衍生物分子2,7-双(4′-(二甲基氨基)苯乙烯基)-9-氢-芴(F1分子)和2,7-双(4′-硝基苯乙烯基)-9-氢-芴(F2分子)中的动力学传播过程以及光限幅效应,分析了两种分子的光限幅特性随传播距离(z)、粒子数密度(N)以及脉冲宽度(τ)的变化情况,并且拟合了两种分子的动态双光子吸收(TPA)截面。计算结果表明,该系列分子具有较大的双光子吸收截面以及较好的光限幅效应。此外,F2分子的末端基团―NO_2与F1分子的末端基团―N(CH_3)_2相比具有更强的得电子能力,因而使得F2分子具有更大的跃迁偶极矩,双光子吸收截面增大,光限幅效应更为明显。

The nanosecond-scale propagations and optical-limiting properties of two fluorene derivatives-2,7-bis（4′-（dimethylamino）-distyryl）-9H-fluorene（F1） and 2,7-bis（4′-（nitro）-distyryl）-9H-fluorene（F2） with different terminal groups are investigated by solving the coupled rate equations and field intensity equation using an iterative predictor-corrector finite-difference time-domain technique.The influence of the propagation distance（z）,particle number density（N）,and pulse width（τ） on the optical-limiting properties and two-photon absorption（TPA） of these molecules is analyzed.The calculations show that both F1 and F2 possess large two-photon absorption cross sections and pronounced optical-limiting properties.In addition,the nonlinear optical properties depend crucially on the terminal groups.F2,with terminal groups of ―NO_2,has much larger dipole moments,an enhanced two-photon absorption cross section,and superior optical-limiting ability compared with F1,which have terminal groups of ―N（CH_3）_2.