研究目的
Investigating the highly sensitive detection of trace hydrogen sulfide (H2S) gas using near-infrared all-optical photoacoustic spectroscopy.
研究成果
The demonstrated near-infrared all-optical photoacoustic spectroscopy system achieves a highly sensitive detection limit of 33 ppb for H2S with a 10 s measurement time. The system's advantages include remote detection capability and immunity to electromagnetic interference, making it suitable for environmental monitoring and industrial applications.
研究不足
The study is limited by the relatively small absorption coefficient of H2S in the near-infrared region and potential interferences from H2O and CO2 in the air. The detection sensitivity could be further improved with mid-infrared lasers, albeit at higher costs.
1：Experimental Design and Method Selection:
The study employs a high-power erbium-doped fiber amplified near-infrared laser for acoustic excitation and a fiber-optic cantilever microphone with a white-light interferometric readout for detecting the second-harmonic photoacoustic signal. A virtual lock-in amplifier is used for sensitivity improvement.
2：Sample Selection and Data Sources:
The PA cell is filled with H2S/N2 gas mixtures of varying concentrations for calibration and detection limit determination.
3：List of Experimental Equipment and Materials:
Includes a high-power erbium-doped fiber amplified near-infrared laser, fiber-optic Fabry-Perot cantilever microphone, white-light interferometric readout system, and gas mass flow controllers.
4：Experimental Procedures and Operational Workflow:
The laser wavelength is locked to 1576.292 nm, and a sinusoidal modulation current is applied. The PA signal is measured using wavelength modulation spectrum and second-harmonic detection methods.
5：292 nm, and a sinusoidal modulation current is applied. The PA signal is measured using wavelength modulation spectrum and second-harmonic detection methods.
Data Analysis Methods:
5. Data Analysis Methods: The demodulated digital photoacoustic signal is processed by a virtual lock-in amplifier, and the detection limit is estimated based on the responsivity of the PA system.
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