研究目的
Developing a stando? laser spectroscopy sensor for simultaneous detection of multiple chemicals using a broadband tunable external cavity quantum cascade laser (ECQCL) and a piezoelectric effect-based detector.
研究成果
The ECQCL gas sensor based on a new type of photodetector has been demonstrated as a versatile and powerful approach for stando? detection of vapor chemicals. The QCTF detector shows slightly better performance compared to the commercial infrared MCT detector. Future work will aim at extending measurements to longer ranges in outdoor environments and optimizing QCTF selection and the signal processing method.
研究不足
The detectivity was mainly limited by the noise of the preamplifier circuit. The influence of air turbulence caused by atmospheric winds and the evaporation process of VOCs requires the monitoring system to have high spectral acquisition rates.
1：Experimental Design and Method Selection:
A custom quartz crystal tuning fork (QCTF) with a high resonant frequency was used as a light detector. The impact of the position of incident light beam excitation with respect to the QCTF on the signal amplitude, resonant frequency, and Q-factor was observed. The influence of incident light intensity and pressure on the intrinsic property of the QCTF was investigated.
2：Sample Selection and Data Sources:
Three volatile organic compounds (VOCs) (i.e., alcohol, acetone, and ether) were used for stando? detection at a distance of 40 m.
3：List of Experimental Equipment and Materials:
A broadband tunable external cavity quantum cascade laser (ECQCL), custom QCTF, and a homemade low-noise transimpedance preamplifier circuit were used.
4：Experimental Procedures and Operational Workflow:
The ECQCL laser beam was collimated and launched onto a distant object, with the reflected light collected and focused onto the QCTF detector. The QCTF detector signal was analyzed using a notebook-based Labview program.
5：Data Analysis Methods:
The vibration intensity signal of the QCTF was directly extracted by fast Fourier transform (FFT) analysis.
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