Irradiance dependence of excitonic nonlinear absorption in Cadmium Sulfide (CdS) nanocrystals has been studied by using Z-scan method with nanosecond laser pulses. The wavelength dependence of nonlinear absorption has also been measured near the excitonic transition of 1S(e)-1S3/2(h). We observe the saturable absorption, which can be described by a third-order and a fifth-order nonlinear process for both 3.0-nm-sized and 2.3-nm-sized CdS nanocrystals. The experimental results show that the excitonic nonlinear absorption of CdS nanocrystals is greatly enhanced with decreasing particle size. A two-level model is utilized to explain both irradiance and wavelength dependence of the excitonic nonlinearity.
@article{arxiv.cond-mat/0507667,
title = {Excitonic nonlinear absorption in CdS nanocrystals studied using Z-scan technique},
author = {J. He and W. Ji and G. H. Ma and S. H. Tang and H. I. Elim and W. X. Sun and Z. H. Zhang and W. S. Chin},
journal= {arXiv preprint arXiv:cond-mat/0507667},
year = {2009}
}