Anomalous resonant nonlinear absorption of excitons in CdSe/ZnS quantum dots

Abstract

We have explained the observed anomalous dependence of colloidal CdSe/ZnS quantum dots' (QDs) absorption upon the intensity of input picosecond laser pulses in the case of one‐photon resonant excitation of exciton 1S3/2(h) – 1S (e) transition – the linear absorption at low intensity is replaced by nonlinear decreasing and then increasing of absorption (!) at high intensities – by saturation effect (state filling) of two‐level system with variable lifetime of the excited state (variable saturation intensity). The lifetime decreases at high excitation due to nonradiative Auger recombination. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)