Investigation of the third-order nonlinear property of Ge-Se-Te glasses at mid-infrared

In this study, a series of Ge₂₀Te_xSe_(80-x) (x = 0, 5, 10, 20, 30, 60, 70) chalcogenide glasses were prepared using conventional melt-quenching technique. Through absorption spectra analysis, the optical Tauc gaps were derived in detail along the increase in the Te content which can be supported by structural changing of glass network shown by Raman spectra. The third-order optical nonlinearity of the glasses at mid-infrared wavelength of 3.1 μm was investigated by traditional Z-scan method. The nonlinear refractive index of the glasses increased with the increase in the Te content, typically the measured nonlinear refractive index of Ge₂₀Se₅₀Te₃₀ glass increased to 8.2 ± 1.2 x 10^-18 m²/W. The relationship between the nonlinear refractive index and the optical band gap was analyzed. (orig.)