Mid-infrared Nonlinear Optical Performances of Ge-Sb-S Chalcogenide Glasses

We report a systematical investigation on the mid-infrared nonlinear performances of Ge-Sb-S glasses. Laser damage threshold (Ith) of Ge-Sb-S glasses was measured under femtosecond pulsed laser incidence ranging between 1.55-3.6 μm. It is found that the Ith has the maximum value at stoichiometric composition. Moreover, the relationship between the refractive index refractive (n0) and nonlinear refractive indices (n2) was obtained, following the semi-empirical Miller’s rule. The n2 shows a nonlinear decay with the increase of wavelength. The multi-photon (up to 7-photon) absorption coefficients of Ge-Sb-S glasses were characterized. The composition Ge25Sb10S65 with high Ith was selected as the core of the designed fiber. A compatible composition Ge25Sb8S67 was chosen as the cladding glass. A 10 μm-diameter-core fiber was made via rod-in-tube method. By pumping a 10-cm-long fiber at 4.8 μm with 170 fs (100 kHz) pulses, we achieved a supercontinuum covering the 3–8 μm spectral range. It indicates that Ge-Sb-S glass family is a type of environment-friendly host materials for mid-infrared nonlinear applications.