Broadband mid-infrared supercontinuum generation in dispersion-engineered As2S3-silica nanospike waveguides pumped by 2.8 μm femtosecond laser

Broadband mid-infrared (IR) supercontinuum laser sources are essential for spectroscopy in the molecular fingerprint region. Here, we report generation of octave-spanning and coherent mid-IR supercontinua in As2S3-silica nanospike hybrid waveguides pumped by a custom-built 2.8 mu m femtosecond fiber laser. The waveguides are formed by pressure-assisted melt-filling of molten As2S3 into silica capillaries, allowing the dispersion and non-linearity to be precisely tailored. Continuous coherent spectra spanning from 1.1 mu m to 4.8 mu m (30 dB level) are observed when the waveguide is designed so that 2.8 mu m lies in the anomalous dispersion regime. Moreover, linearly tapered millimeter-scale As2S3-silica waveguides are fabricated and investigated for the first time, to the best of our knowledge, showing much broader supercontinua than uniform waveguides, with improved spectral coherence. The waveguides are demonstrated to be long-term stable and water-resistant due to the shielding of the As2S3 by the fused silica sheath. They offer an alternative route to generating broadband mid-IR supercontinua, with applications in frequency metrology and molecular spectroscopy, especially in humid and aqueous environments. (C) 2021 Chinese Laser Press

Automated summary

This paper reports the generation of broadband mid-infrared supercontinuum lasers using As2S3-silica nanospike hybrid waveguides, as well as the fabrication and investigation of linearly tapered millimeter-scale waveguides for the first time. These waveguides exhibit broader spectra, improved spectral coherence, long-term stability, and water resistance, offering an alternative route for generating broadband mid-IR supercontinua with applications in frequency metrology and molecular spectroscopy, especially in humid and aqueous environments.