Investigation of optical nonlinearity in surface-enhanced GSS/Ag bilayer thin films

Abstract Chalcogenide glass is widely regarded as an outstanding nonlinear optical amorphous material. The modulation of optical nonlinearity via micro- and nanostructuring has emerged as a novel and promising research direction in the field of chalcogenide glasses. In this study, silver (Ag) islands formed in annealed Ag films were utilized as micro- and nanostructures. As the annealing temperature increased, optimal Ag island-like structures formed at 250 °C. With further increases in annealing temperature, the Ag islands either shrank in size or disappeared. The Ge 28 Sb 12 Se 60 (GSS)/Ag bilayer films consisted of a 20 nm Ag bottom layer, which was either unannealed or annealed, and a 60 nm GSS top layer. The results showed that when the annealing temperature of the Ag film reached 250°C, the nonlinear absorption coefficient of the GSS/Ag bilayer thin film attained a maximum value of 2.16 × 10 −6 m W −1 , resulting from the local field enhancement effect, which is approximately three times that of the 60 nm GSS film. Moreover, the nonlinear refractive index decreased as the annealing temperature increased. The change in nonlinear parameters makes this material a promising candidate for optical limiting and photothermal modulator applications. The findings of this study provide valuable insights into improving the nonlinear properties of chalcogenide glasses and developing high-performance integrated photonic devices.