取代基对卟啉类化合物三阶非线性光学特性的影响

主要采用吸收光谱、荧光光谱和皮秒Z-扫描等实验方法研究了三种不同取代基的卟啉化合物5,10,15,20-四对羟基苯基卟啉T(4-HP)P]、5,10,15,20-四对酯基苯基卟啉T(4-EP)P]和5,10,15,20-四对溴苯基卟啉T(4-BrP)P]的光学及非线性光学性质,并从离域电子共轭结构理论和共振、非共振增强理论进行了分析。结果表明,强给电子基团取代的T(4-HP)P的吸收和荧光发射带比弱给电子基团取代的T(4-EP)P及吸电子基团取代的T(4-BrP)P有明显红移;三种样品均具有正的三阶非线性极化率χ(3),强的给电子能力和共振增强使得T(4-HP)P的三阶极化率比T(4-BrP)P增强了近两个量级,并在532 nm光激发时,χ(3)具有最大值6.81×10-10esu。

Substituent Effect on the Third-Order Nonlinear Optical Properties of Porphyrin Compounds

The linear and nonlinear optical properties of three porphyrin compounds with different substituents, meso-tetra (p-hydroxyphenyl) porphyrin ［T(4-HP)P］, meso-tetra (p-esterphenyl) porphyrin ［T(4-EP)P］ and meso-tetra (p-bromophenyl) porphyrin ［T(4-BrP)P］ have been investigated by using absorption spectroscopy, fluorescence spectroscopy and picosecond Z-scan technique. The optical properties of the three compounds were discussed on the basis of π-electron conjugated structures and resonant/non-resonant enhancement. The experimental results showed that the absorption and fluorescent emission bands of T(4-HP)P substituted by stronger donating electron group shift towards lower photon energy, in comparison of T(4-EP)P substituted by weaker donating electron group and T(4-BrP)P substituted by accepting electron group. All the three compounds had positive third-order nonlinear susceptibilities χ(3). With the resonant excitation at 532 nm, the third-order nonlinear susceptibility χ(3) of T(4-HP)P showed a maximum of 6.81×10-10 esu, which is two orders of magnitude larger than that of T(4-BrP)P.