激发态分子内质子转移有机分子HBT的三阶非线性光学特性

Optical nonlinearities of excited state intramolecular proton transfer molecule HBT

以532nm皮秒脉冲作抽运光,采用单光束Z-扫描技术对具有激发态分子内质子转移效应的有机分子2-(2′-羟基苯基)苯并噻唑(HBT)在其双光子吸收区的非线性光学特性进行了研究.实验结果表明,对532nm波长的光,HBT分子存在明显的双光子吸收.通过拟合开孔Z-扫描实验数据,求解了HBT分子在其双光子吸收区的非线性吸收系数,并探讨了抽运光强度对介质双光子吸收效应的影响.采用高斯分解法,通过拟合闭孔Z-扫描除以开孔Z-扫描数据,理论推导并计算了在介质对抽运光存在非线性吸收的情况下HBT分子的非线性折射率,以及不同入射光强度时HBT分子的三阶非线性极化率实部和虚部的值.计算结果表明,理论分析与实验结果较好地符合,这些结果为进一步研究和开发此类材料的应用提供了理论与实验依据.

The optical nonlinearity,including the nonlinear absorption,the nonlinear refraction and the third-order nonlinear polarizability of 2-（2＇-hydroxyphenyl）benzothiazole（HBT） in cyclohexane,has been investigated using a single-beam Z-scan technique.The experiment and calculations show that HBT molecules have obvious two-photon absorption（TPA） effect under the 532 nm picosecond pulsed laser irradiation.The values of the TPA coefficient β0 for different pulse irradiance and the corresponding imaginary part χI（3）of the third-order nonlinear polarizability were determined according to the open-aperture Z-scan results.Then we measured the nonlinear refractive index γ and the real part χ（R3）of the third-order nonlinear polarizability of HBT,and calculated these two nonlinear parameters with ＂Gaussian decomposition＂ method according to the close-aperture Z-scan and open-aperture Z-scan results,when the nonlinear refraction was accompanied by nonlinear absorption.The theoretical results agree very well with the experimental results.This work provides a theoretical as well as a experimental basis for further research and development of the application of the material.