Optical Properties of Ag-SiO2 Composite thin films by Sol-Gel method

초록

Glass has long been used as a versatile optical material because of the diverse properties, such as refractive index, dispersion, and selective absorptivity etc. When depends upon its composition and processing conditions. However, to meet the specific optical applications, the modifications of the surface properties of glass are necessary and the modifications increase its value to the optical designer. Embedding small metal particles in glasses have been received good attractions for optical devices. It is known that the third-order optical nonlinearity in the glasses doped with metal particles is strongly enhanced near the surface plasmon resonance frequency. The sol-gel method has been succesfully applied to obtain coatings for optical properties. Coating composition is designed according to the final properties to be obtatined e.g., nonlinear response, metal nanoparticles, light waveguides, photochromism, electrochromism and photoluminescence, etc. Novel metals doped films have been prepared by sol-gel method using different precursors and processes. In this study, thin films containing silver colloids were prepared on commercial soda lime and Bk7 glass substrates by the sol-gel method and applying on the optical devices. The sol was prepared from 1:0.24:3.75:2.2 molar ratios of Si(OC2H5)4 : AgNO3 : H2O : C4H10O2. HNO3 of 0.5N was used as hydrolysis catalyst. The silver doped silica thin film was successfully prepared by the spin-coating method. The optical absorption spectra of films annealed in air at various temperatures and silver molar ratios were measured. The experimental data were compared with simulations of Mie's theory. The diffraction gratings of Ag-SiO2 thin films were prepared by 488nm Ar-ion laser. The characteristics of diffraction gratings were also examined.