Third-order nonlinear optical properties of Ge-As-Te chalcogenide glasses in mid-infrared
Qiuli Li, Rongping Wang, Fu Xu, Xunsi Wang, Zhiyong Yang, Xin Gai
Abstract
Third-order nonlinear optical properties of Ge 10 As x Te 90-x chalcogenide glasses were investigated utilizing the Z-scan method at the mid-infrared wavelengths of 2.5 and 3.0 µm. The compositional dependence of the third-order nonlinearity was analyzed, and their correlation with the refractive index and the optical bandgap was discussed. The results show that nonlinear refractive index n 2 can be significantly enhanced by the addition of tellurium, and larger n 2 values are observed at 3.0 µm rather than 2.5 µm due to the two-photon resonance effect, and the maximum of n 2 is 4.96 × 10 −13 cm 2 /W at the composition of Ge 10 As 20 Te 70. In addition, the experimental results are in good agreement with the semi-empirical Miller’s rule whilst the variation of dispersive n 2 values are in relatively good coincidence with the theoretical model by Sheik-Bahae et.al. for direct bandgap semiconductors.