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Fiber‐enhanced Raman spectroscopy is applied actively for gas analysis. Hollow‐core anti‐resonant fibers (HC‐ARFs) with low loss and low spatial overlap between core and cladding modes show the potential of low background. We integrated an HC‐ARF into the Raman system, collected the forward scattering radiation with a lens‐coupled imaging spectrometer, and filtered most of the background through selection of region of interest. The limits of detection (LODs) of this system were determined as 1.2 ppm·bar for CH4, 2.9 ppm·bar for C2H6, 1.6 ppm·bar for C2H4, 2.7 ppm·bar for C2H2, 13.8 ppm·bar for H2, and 16.7 ppm·bar for CO with the excitation laser of 200 mW and the exposure time of 60 s. In addition, the LOD was better than 2.5 ppm·bar for H2S. By the detection of gas samples with the critical detectable concentration, it was proven that the estimated values of LOD from the preceding experimental results are reliable and the system had practical detectability. The gas samples we tested are relevant for multiple fields such as industrial process control and environment monitoring, showing the diversified application prospects of the Raman gas analysis system based on HC‐ARF. [ABSTRACT FROM AUTHOR]

We demonstrated high‐resolution continuous‐wave (CW) coherent anti‐Stokes Raman spectroscopy of gaseous samples in a single ring hollow‐core photonic crystal fiber. Pump beam and Stokes beam were provided by CW single longitudinal mode lasers. These narrow linewidth lasers brought the benefit of a spectral resolution of 99 MHz. The high resolution allowed a measurement of a linewidth 0.3 GHz of the ν1 transition of CO2 in a gas mixture with partial pressure of 0.15 MPa and total pressure of 0.9 MPa. Pump beam from a tunable dye laser and Stokes beam from an external cavity diode laser were coupled into the fiber containing gaseous CO2. Fundamental mode phase matching was achieved by tuning gas pressure. The long interaction length provided by the hollow fiber yielded a 60‐dB increase in the anti‐Stoke signal. The attained signal to noise ratio of the spectrum of ν1 component of 0.6‐MPa CO2 was ~25,000 with 152‐mW pump power and 1.4‐mW Stokes power. [ABSTRACT FROM AUTHOR]