CdSe/ZnS核-壳结构量子点的非线性光学吸收

利用开孔Z扫描技术研究了吸收峰分别为553 nm和503 nm的两种尺寸CdSe/ZnS核-壳结构量子点溶液的非线性吸收性质.对于532 nm,6 ns激光脉冲,两种材料均表现出饱和吸收向反饱和吸收转化的现象.数值模拟结果表明：当吸收峰波长大于激光波长时,饱和吸收过程由快、慢两种机制组成,分别对应基态载流子被激发至不同的激发态,而强光下的反饱和吸收与快过程相关；当吸收峰波长小于激光波长时,饱和吸收主要由快过程机制引起,强光下的反饱和吸收源自激发态吸收和双光子吸收.我们的研究结果表明半导体量子点是研制光开关和光限制器件的理想候选材料.

Nonlinear Absorption of CdSe/ZnS Core-Shell Quantum Dots with Nanosecond Laser Pulse

The nonlinear optical absorption of CdSe/ZnS quantum dots in toluene with two different sizes are investigated using open aperture Z-scan with 6ns laser pulse at 532 nm. Nonlinear optical absorption of two samples display a switch over from saturation absorption (SA) to reverse saturation absorption (RSA) with increasing input laser intensity. When laser wavelength (532 nm) is smaller than the absorption peak (553 nm), it behaves two different SA processes which are related to different excited states at low intensity and RSA caused by excited state absorption (ESA) at high intensity. When laser wavelength is larger than the absorption peak (503 nm), it behaves SA related to one excited states at lower intensity and RSA caused by excited state absorption (ESA) and two photon absorption (TPA) at high intensity. Our results show that quantum dots are good candidate materials for the fabrication of optical switching and optical limiting device.