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以脉宽为50fs、波长为800nm、重复频率为1kHz的飞秒激光作为激发光源,利用Z扫描技术研究了CdSeS量子点(QDs)/聚苯乙烯(PS)复合薄膜在非共振区的三阶非线性光学特性。实验结果表明,CdSeS QDs/PS复合薄膜在800nm光的激发下具有较大的非线性吸收效应;观察到随着激光强度的增加,复合薄膜从饱和吸收(SA)向反饱和吸收(RSA)转变。该反饱和吸收效应主要源于CdSeS量子点的双光子吸收(TPA)。并且,双光子吸收系数β随着激光强度的增加而增加。当激光强度为4.2GW/cm2和16.8GW/cm2时,β分别为1.6×10-8 cm/W和2.8×10-8 cm/W,与已报道的量子点相比较高出1个数量级;非线性折射率n2分别为-6.2×10-11 cm2/W和2.7×10-12 cm2/W,与已报道的量子点相比较高出2个数量级。结果表明,CdSeS QDs/PS复合薄膜在光开关和光限幅等方面具有较大的潜在应用价值。
Using the femtosecond laser with a pulse width of 50fs, a wavelength of 800nm and a repetition frequency of 1kHz as the excitation light source, the QSecondary quantum dots (QDs) / polystyrene (PS) Nonlinear optical properties. The experimental results show that the CdSeS QDs / PS composite film has a large non-linear absorption effect under the excitation of 800 nm light. The change of the composite film from the saturated absorption (SA) to the reverse saturation absorption (RSA) with the increase of the laser intensity . The reverse saturating absorption effect is mainly due to the two-photon absorption (TPA) of CdSeS quantum dots. Also, the two-photon absorption coefficient β increases as the laser intensity increases. Β were 1.6 × 10-8 cm / W and 2.8 × 10-8 cm / W, respectively, when the laser intensity was 4.2GW / cm2 and 16.8GW / cm2, which was one order of magnitude higher than the reported quantum dots. The nonlinear refractive indices n2 are -6.2 × 10-11 cm2 / W and 2.7 × 10-12 cm2 / W, respectively, which are two orders of magnitude higher than the reported quantum dots. The results show that CdSeS QDs / PS composite films have great potential applications in optical switching and optical limiting.