以脉冲宽度为35 ps, 基频为1064 nm的Nd∶YAG锁模激光器二倍频532 nm的激光作激发, 利用Z-扫描技术研究了CdSeS量子点的光学非线性特性。实验结果表明CdSeS量子点在532 nm光激发下具有很大的非线性吸收效应, 该吸收效应来自于光学三阶效应引起的双光子吸收。在不同的入射光强下观测了CdSeS量子点的Z-扫描曲线, 实验表明, CdSeS具有大的非线性折射率1.9×10-8 esu和大的双光子吸收截面25283 GM, 比现在使用的ZnS量子点高出近2个数量级。

The optical nonlinear properties of CdSeS quantum dots (QDs) are investigated by Z-scan technique using the model locked Nd∶YAG laser second harmonic radiation (λ wavelength of 532 nm, pulse width of 35 ps). The experimental results show that the quantum dots have large two-photon absorption (TPA) which originates from the third order optical nonlinearity effect. According to the absorption and fluorescence spectra, it is found that this nonlinear absorption originates from the TPA of CdSeS quantum dots. Z-scan curve of CdSeS quantum dots is measured under different incident intensities, and the experimental results show that the quantum dots have nonlinear refractive index of 1.9×10-8 esu and average TPA cross section of 25283 GM, which are two orders higher than values of commonly used ZnS QDs.