水溶性CdTe量子点的三阶光学非线性极化特性

The property of third-order optical nonlinear susceptibility ofwater soluble CdTe quantum dots

利用超短脉冲Z扫描技术和光学Kerr效应研究了以巯基丙酸为稳定剂的CdTe量子点水溶液的三阶光学非线性极化特性.在532nm,30ps和800nm,130fs脉冲激光激发下,发现分别具有正负相反取值的三阶光学非线性折射率,自由载流子吸收和双光子吸收分别是这两种脉冲激光激发下三阶光学非线性吸收的起因.测量得到CdTe量子点的三阶光学非线性极化率约为CS2的3·2倍,在520—700nm光谱区的CdTe量子点的光学响应时间小于400fs.

The property of optical nonlinear susceptibility of the CdTe quantum dots （QDs） has been studied by using Z-scan and optical Kerr effect technique. Laser-induced sign reversal of the nonlinear refractive index of CdTe quantum dots appears under femtosecond and picosecond pulse excitation. Two-phonon absorption and free carrier absorption in the nanometer-sized CdTe are the possible origins of the nonlinear absorption. This material has the ultrafast response time of less than 400 fs in optical switching operation, and the peak Kerr transmittance is found to be 3.2 times greater than that of the standard CS2 liquid Kerr medium.