Octave-spanning supercontinuum generation in As2S3 waveguides pumped by a mid-infrared femtosecond-Raman soliton fiber laser

Abstract

For mid-infrared supercontinuum generation in fiber-laser-pumped As₂S₃ waveguides, the selection of pumping wavelengths and coupling mechanisms significantly influences the extent of spectral long-wavelength edge broadening. The Raman soliton self-frequency shift (SSFS) technique enables pulses to be turned to longer wavelengths in fibers; however, it is limited to 2.4 μm in silica-based fibers. GeO₂-doped silica fibers are particularly suitable for efficient mid-infrared soliton generation and lensed structure processing due to their wider low-loss infrared transmission window and enhanced mechanical strength compared to conventional silica or soft-glass fibers. In this work, we demonstrate mid-infrared supercontinuum (SC) generation in an As₂S₃ slab waveguide using femtosecond solitons produced by SSFS in a GeO₂-doped silica fiber as the pump source. By integrating an all-fiber source, a home-built GDF lensed fiber, and a carefully engineered As₂S₃ waveguide, we achieved a 1.8-octave-spanning SC with the long-wavelength edge extending up to 2.93 µm. Simulations of pulse evolution in fibers and waveguides show good agreement with experimental results. This work provides a practical platform for on-chip optical sensing and communication.