Preparation of Zinc-Doped CdSe Nanoparticles and Determination of Their Nonlinear Optical Properties using Z-Scan Technique in Thick Media

The present work aims at the synthesis of Zinc-doped CdSe ( Zn : CdSe ) nanoparticles with average size near the Bohr radius by wet chemical method. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), UV-Vis spectrometer is used for the determination of bandgap and crystallite size is estimated using Debye–Scherrer formula and Brus equation. The nonlinear optical property that is excitonic nonlinear absorption and the wavelength dependence of nonlinear absorption has also been measured near the excitonic transitions involving the lowest electron state (1S) and one of the hole states 1S3/2(h). We observe the saturable absorption (SA), which can be described by a third-order and a fifth-order nonlinear process for Zn : CdSe nanocrystals. The irradiance and wavelength dependence of the excitonic nonlinearity are explained by two-level model. The calculations have been performed with the help of Z-scan experimental setup using Handy Compact Q-switched pulsed Nd:YAG laser (HYL-101 Quanta System).