Photoacoustic methane detection assisted by a H₂-filled anti-resonant hollow-core fiber laser

The anti-resonant hollow-core fiber (ARHCF) lasers in the near-infrared (NIR) and mid-infrared (MIR) spectral domain show a great potential for spectroscopy and high-resolution gas detection. In this work, we demonstrated the generation of a frequency-comb-like Raman laser with high pulse energy spanning from ultraviolet (UV) (328 nm) to NIR (2065 nm wavelength) based on a hydrogen (H₂)-filled 7-ring ARHCF. The H₂-filled ARHCF is pumped with a custom-laser at 1044 nm with ∼ 75 μJ pulse energy and ∼ 3.7 ns pulse duration. Through stimulated Raman scattering process, we employed the sixth-order rotational Raman Stokes located at ∼ 1650 nm as a case example to demonstrate how the developed high-energy and narrow-linewidth laser source can effectively be used to detect CH₄ in the NIR-II region using the photoacoustic modality. We reported the efficient detection of CH₄ with sensitivity as low as ∼ 550 ppb with an integration time of ∼ 40 s. In conclusion, the main goal of this work is to demonstrate and emphasize the potential of the gas-filled ARHCF laser technology for compact next-generation spectroscopy across different spectral regions.