The second order nonlinear optical properties of sandwich thulium bisphthalocyanine (TmPc2) molecule Langmuir-Blodgett (LB) films were investigated using the second harmonic generation (SHG) method. The dependence of the second harmonic intensity on the incident angle of the fundamental beam was measured and the mechanisms of nonlinearity were discussed briefly. The experimental results indicated that the second harmonic signal intensity was very strong and its maximum was obtained at an incident angle of 45°. The second order nonlinear optical susceptibility X(2) was about 1.152×10-8 esu and the hyperpolarizability p was about 1.905×10-30 esu. By measuring the polarization properties of the second harmonic signal for the LB film and comparing this with the theoretical analysis, we found that the origin of the second harmonic generation was attributed to the electric quadrupole mechanism for the TmPc2 molecule.%利用二次谐波产生(SHG)方法研究了中心对称分子稀土夹心双酞菁铥(TmPc2) Langmuir-Blodgett(LB)膜二阶非线性光学特性,测量了二次谐波强度随入射基频光入射角的关系,并对其二阶非线性产生机制进行了讨论.实验结果表明,TmPc2分子LB膜具有较好的二次谐波信号,二次谐波信号强度的最大值在基频光入射角为45°的地方,其二阶非线性极化率X(2)和分子超极化率β分别为1.152×10-8和1.905× 10-30esu.通过测量样品二次谐波信号的偏振特性,并与理论分析相比较,得出其二阶非线性起源于电四极子作用机制.
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