Study on the nonlinear optical properties of Ag/CdS nanocomposite films

Using physical vapor deposition, cadmium sulfide (CdS) films, Ag nanoparticle films, and Ag/CdS composite films were successfully fabricated on substrates. The surface morphology, crystal structure, and optical bandgap of the samples were systematically characterized using scanning electron microscopy, x-ray diffraction, and ultraviolet–visible spectrophotometry, respectively. Using femtosecond Z-scanning technology, the nonlinear optical properties of composite materials were investigated at a wavelength of 800 nm. By adjusting the laser energy, the evolution of their nonlinear optical response with excitation intensity was systematically examined. The results indicate that, in comparison to single-component thin films, the Ag/CdS composite demonstrates significant characteristics of nonlinear absorption and nonlinear refraction. These characteristics are specifically manifested as saturated absorption behavior and self-defocusing effects. Notably, the incorporation of Ag nanoparticles effectively enhances the nonlinear optical response of the composite system, with this enhancement becoming increasingly pronounced as the Ag deposition power rises. Furthermore, the saturation absorption effect of the composite material gradually intensifies with rising laser energy. These outstanding nonlinear properties indicate that Ag/CdS composites hold significant application potential for integrated optoelectronic functional devices.