Picosecond Z-scan investigations of optical nonlinearity in CdS nanostructure films

Abstract

Materials with large optical nonlinearity and fast response are essential requirements for the development of photonics devices such as optical switches and optical limiters. This paper reports on the linear and nonlinear optical properties of CdS nanoclusters in the size regime of strong quantum confinement synthesized by methods of colloidal chemistry. Stable films of optical quality are obtained by drying the colloidal solution. CdS nanoclusters of 3.5 nm were obtained by changing the concentration of the precursors. The nanocluster films thus prepared are found to be very stable. Large optical nonlinearity is observed in the films in the resonant wavelength region. The nonlinearity appears to originate predominantly from two-photon absorption.