聚芳香杂环甲烯的三阶非线性光学效应与时间分辨光克尔效应

合成了一系列聚芳香杂环甲烯,包括聚吡咯甲烯和聚噻吩甲烯.采用四波混频法研究材料的共振三阶非线性光学效应(λ＝532nm),其共振二阶超分子极化率γ三阶非线性光学系数分别达到10^-30esu和10^-8esu.选择具有良好溶解性、成膜性的聚吡咯对二甲氨基苯甲烯(PPDMAB),采用飞秒时间分辨光克尔效应方法研究材料的非共振三阶非线性光学效应(λ=790nm).实验表明,翠绿亚胺碱溶液的光克尔信号仅表现一超快响应的成分,归功于π电子云扭转产生的非共振激发.PPDMAB的非共振二阶超分子极化率γ三阶非线性光学系数分别达到γ=5.78×10^-32esu和χ⁽³⁾=1.26×10^-10esu.

Third-order Optical Nonlinearity and the Time-resolved Optical Kerr Effect of Poly(heteroarylene methines)

A series of poly(heteroarylene methines) containing one pyrrole or thiophene ring alternating with a carbon atom in the main chain were synthesized. The resonant third-order optical nonlinearity at 532 nm was studied by using degenerate four-wave mixing (DFWM) techique. The resonant second-order hyperpolarizabilities γ and third-order nonlinear optical susceptibility χ(3) were up to 10-30esu and 10-8esu respectively. Poly{pyrrole-2,5-diyl(p-N,N-dimethlamino)benzylidene]} (PPDMAB) was chosen to be further studied mainly due to its good solubility and film forming performance.Time-resolved Optical Kerr effect (OKE) of PPDMAB was investigated with femtosecond laser pulses at 790 nm. Only an ultrafast component of OKE of PPDMAB was observed and its dephasing time was 84.7 fs, which is attributed to π-electron-cloud distortion occurring upon the non-resonant excitation. The off-resonant second-order hyperpolarizabilities γ and third-order nonlinear optical susceptibility χ(3) of PPDMAB were also determined by transient OKE. The results show that PPDMAB exhibit large off-resonant nonlinearities γ as large as γ=5.78×10-32esu, for each structural units and χ(3) as large as χ(3)=1.26×10-10esu for the material have been obtained.