Structure and Third-order Optical Nonlinearity Performance of Ge-Sn-Se Doped TiO_2 Glass-ceramics at 1550 nm

Ti O2 manifested as nucleating agent was introduced in Ge-Sn-Se ternary chalcogenide glass by heat-melt method. Then the samples were heat-treated for different time. The experiment results indicated that heat treatment process can lead to the precipitation of Ge Se2 monoclinic crystals and Sn Se2 hexagonal crystals in the Ti O2 doped Ge-Sn-Se glass with the heat treatment time increasing. The variety of UV cut-off wavelength, optical band gap and Urbach energy revealed that the number of defect units in glass-ceramic samples increased with the increment of heat treatment time. The third-order optical nonlinearity of all samples was measured by Z-scan technology at 1550 nm. The results showed that the formation of nano-crystals in glass-ceramic samples can improve the third-order nonlinear refraction index significantly due to the strong local field effect. The largest value of nonlinear refraction index reached 5.75×10-16 m2/W, and the sample heat-treated for 3 h was considered as a high-quality nonlinear optical material for its high nonlinear refraction index as well as high figure of merit.