A Trace C2H2 Detection Based on Near-Infrared Dual-Comb Spectroscopy

To achieve low-concentration measurement using near-infrared dual-comb spectroscopy (DCS), this study presents a trace C₂H₂ detection using near-infrared DCS. A multi-pass gas cell is employed to extend the optical path length, improving the sensor's sensitivity. Signal post-processing via interpolation method is applied to reduce noise and achieve a flatter dual-comb. The sensor's sensitivity and transient characteristics are evaluated by selecting absorption lines at 6526.53, 6529.17, and 6531.78 cm⁻¹, with the experimental profile being well-fitted by a Voigt function. The stability of the system is confirmed with a C₂H₂ concentration of 200 ppm over a 2.5 h observation period, showing a stability better than 2.305 × 10⁻². Allan variance analysis indicates an optimal integration time of 597 s, yielding a minimum detection limit of 6.15 × 10⁻⁴ for absorbance and 350 ppb for concentration. Additionally, the detection of nine absorption lines demonstrates the multi-peak measurement capability, with deviations ranging from 0.059% to 12.496%.