On-chip near-infrared multi-gas sensing using chalcogenide anti-resonant hollow-core waveguides

On-chip infrared spectroscopic gas sensing using a hollow-core anti-resonant reflecting optical waveguide (ARROW) with a large external confinement factor (ECF) was rarely reported due to the complex fabrication process and polarization dependence. Alternatively, we proposed ARROW gas sensors using chalcogenide (ChG) anti-resonant layers which require thermal evaporation and epoxy resin bonding for fabrication instead of the complicated wafer bonding process. Polarization characteristics and ethylene (C₂H₂) sensing performance at 1.532 μm were measured for two ARROW sensors with four-side (WG_A) and three-side (WG_B) anti-resonant layers around the hollow-core. Due to a symmetric structure, the 1 cm-long WG_A sensor exhibits polarization-insensitive characteristics, which does not require an additional polarization controller for integrated on-chip sensors and enhances the stability and reliability of the sensor under fluctuating polarization states. A high ECF of 71% and a 1σ limit of detection (LoD) of ∼23 parts-per-million (ppm) for WG_A were achieved at an averaging time of 39.2 s. The broadband multi-gas detection capability of WG_A was verified through C₂H₂ detection at 1.532 μm and CH₄ at 1.654 μm, highlighting the potential of ARROWs for on-chip multi-gas sensing.