High-Sensitivity Dual-Cavity UV-LED Photoacoustic Gas Sensor for Sulfur Dioxide Detection

An ultraviolet light-emitting diode (UV-LED)-based photoacoustic spectroscopy (PAS) sensor is developed for trace sulfur dioxide (SO₂) detection. Different from the conventional photoacoustic (PA) system, this system incorporates a gas absorption cell between the LED and photoacoustic cell (PAC) to pass the target gas. The PAC filled with stationary 50 ppm SO₂ is used as the detection module, so it can avoid the interference of gas flow. Meanwhile, the differential Helmholtz resonance structure serves as the PAC to match the divergent LED light source, suppress environmental noise, and enhance the PA signal. The experimental results demonstrate a long-term noise standard deviation of 0.278 mV, a signal-to-noise ratio (SNR) of 71.94, and a minimum detection limit (MDL) of 69.5 ppb achieved at 1 s integration time. This gas detecting system has the characteristic of high sensitivity, and it has potential for open-path trace gas detection applications in hazardous environments.