研究目的
Investigating the use of a new multi-point sensor for C2H2 detection based on photoacoustic spectroscopy and acousto-optic Q-switched fiber laser.
研究成果
The intra-cavity multi-point sensor achieved a good linear response to C2H2 concentration with MDLs of 1.73 ppmv, 7.82 ppmv, and 1.93 ppmv for the three PAS cells. The sensor's performance can be enhanced by optimizing the PAS cell design and laser power.
研究不足
The difference in system constants and photoacoustic conversion efficiency among the PAS cells led to variations in detection limits. The sensor detection limit can be further improved by using a novel PAS cell with a high Q/f0 ratio and increasing the laser power.
1：Experimental Design and Method Selection:
The study employed an acousto-optic Q-switched fiber laser as the excitation source and three transmission-type PAS cells placed inside the laser cavity for simultaneous C2H2 detection.
2：Sample Selection and Data Sources:
C2H2 samples with known concentrations from 200 ppmv to 1400 ppmv were used.
3：List of Experimental Equipment and Materials:
The setup included an erbium doped fiber (EDF), an acousto-optic modulator (AOM), fiber Bragg grating (FBG), and three custom-made transmission-type PAS cells.
4：Experimental Procedures and Operational Workflow:
The laser was modulated at 5 kHz, matching the resonant frequency of the PAS cells. The photoacoustic signals were detected and demodulated using a lock-in amplifier.
5：Data Analysis Methods:
The signal-to-noise ratios (SNR) and minimum detection limits (MDL) were calculated from the experimental results.
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erbium doped fiber
MP980
OFS
Used as the gain medium in the acousto-optic Q-switched fiber laser.
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acousto-optic modulator
T-M200-0.1C2J-3-F2P
Gooch&Housego
Used as a Q-switching element in the fiber laser.
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electret condenser microphone
EK-23029
Knowles
Detected the photoacoustic wave in the PAS cells.
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980 nm pump laser
S26-7602-140
JDSU
Forward pumped the EDF.
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signal generator
FY2300A
Feel Tech
Provided modulation signal for the AOM.
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pre-amplifier
CA3140E
Intersil
Converted the weak current signal generated by the microphone to a voltage signal.
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lock-in amplifier
HF2LI
Zurich Instruments
Demodulated the photoacoustic signals.
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