Two Photon Absorption in Nanostructure Wide Band Gap Semiconductor CdS Using Femtosecond Laser

Strong nonlinear absorption in CdS nanoparticles of dimensions in the range 4 - 50 nm when irradiated with a femtosecond pulsed laser at 800 nm is observed. The CdS nanoparticles sizes were controlled by changing the reaction time of aqueous solutions of thiourea and cadmium chloride. The structure of the prepared CdS nanoparticles were tested and their optical properties were investigated and the nonlinear absorption coeffi-cients were measured using a fully computerized z-scan unit. It is found that the formation of the CdS nanos-tructuresfor are responsible for the observation of the strong tow photon absorption.