末端基团对芴类衍生物分子非线性光学性质的影响

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―NO2与F1分子的末端基团―N(CH3)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。

Influence of Terminal Group on Nonlinear Optical Properties of Fluorene Derivatives

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 ―NO₂, 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(CH₃)₂.