Mid-infrared supercontinuum generation in chalcogenide fibers with high laser damage threshold

Laser damage thresholds (I-th) at 1.03 mu m, as well as third-order nonlinear refractive indices (n(2)) and two photon absorption coefficients (beta) at 1.55 mu m of a number of Ge-As-S glasses were measured and systematically studied. The glass with the composition Ge0.12As0.24S0.64 showed a high I-th and the maximum figure of merit (f(m) = n(2)/(beta.lambda)), and therefore was selected as the core material for the fabrication of a step-index fiber. A compatible glass with the composition Ge0.18As0.1S0.72 was chosen as the cladding material. Based on the dispersion calculations, the fiber with a core diameter of similar to 7-10 mu m was designed. The designed fiber was fabricated by a multiple step rod-in-tube method. When the fiber with a core diameter of similar to 9 mu m and a length of 13.5 cm was pumped by similar to 170 fs pulses (1 MHz) at 4.5 mu m, the mid-infrared supercontinuum (SC) covering 1.3-8.1 mu m was generated. These results demonstrate the good potential of Ge-As-S chalcogenide fibers for producing high-brightness broadband mid-infrared SC light sources. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement