Investigation of the third-order optical nonlinear enhancement properties of Ag doped chalcogenide glass films

Chalcogenide glass is widely recognized as an excellent nonlinear optical material. Enhancing its nonlinear optical properties through metal doping has emerged as a prominent research avenue in the field of chalcogenide glass. In this paper, silver (Ag) doped Ge28Sb12Se60 (GSS) chalcogenide glass films with different concentrations were prepared by co-evaporation method. The nonlinear absorption coefficients (β) of different samples were investigated by open-aperture top-hat Z-scan experiments and pump-probe experiments, and the nonlinear refractive index (γ) values were determined using the Tichy-Ticha relation. The results showed that the nonlinear absorption of GSS thin films can be improved by Ag doping. The nonlinear absorption coefficient β exhibits the maximum enhancement of about 2.5 times at 8.3% concentration, with the maximum β reaching 1.83×10-6m/W. The nonlinear absorption mechanism observed in the thin films can be attributed to free carrier absorption, and the free carrier lifetime is positively correlated with the Ag doping concentration. Within the selected Ag concentration range, the nonlinear refractive index (γ) of Ag doped chalcogenide glass films continues to increase, reaching about 3 times at 30.7% concentration, with the maximum γ being 4.643×10-17 m2/W. Additionally, the third-order nonlinear polarizability (χ(3)) values can be increased from 1.014×10-11esu to 3.314×10-11esu with increasing Ag concentration. The research results in present paper are of great significance for further exploration of the optical nonlinear enhancement properties and carrier recombination dynamics in chalcogenide glass.