Photo-thermal spectrum trace gas detection device and method based on cavity enhancement

Abstract

The invention discloses a photo-thermal spectrum trace gas detection device and method based on cavity enhancement. Llow-frequency sawtooth waves generated by a signal generator and high-frequency sine waves generated by a lock-in amplifier are sent into a summator, and superposed signals form modulation signals of laser wavelength; a modulation signal is sent into a laser controller, the wavelength of laser output by the tunable semiconductor laser is changed through a temperature module and a current module, the laser enters a gas chamber of gas to be measured after passing through a laser collimation system, and target gas to be measured absorbs part of laser energy; laser is emitted from the gas chamber of the gas to be measured and then is focused to the root position of a quartz tuning fork interdigital through a light spot of a focusing lens, a generated vibration signal is converted into an electric signal due to photoinduced thermoelastic deformation and a piezoelectric effect, and the electric signal is input into a lock-in amplifier for harmonic signal acquisition; the harmonic data are finally input into a computer to be processed, and the gas concentration is inverted. The device has the advantages of high sensitivity, low cost, non-contact measurement and the like.

Description

technical field [0001] The invention relates to a cavity-enhanced photothermal spectrum trace gas detection device and method. Background technique [0002] Quartz-enhanced photothermal spectroscopy technology is a new type of trace gas detection technology proposed by Ma Yufei and others in 2018. In recent years, many research institutes at home and abroad have used this technology to achieve high sensitivity, good selectivity, and fast response. Fast, non-contact gas measurement. The technology takes advantage of the light-absorbing properties of quartz materials and converts the absorbed light energy into heat energy. Due to the thermoelastic effect, the surface of the quartz tuning fork will be mechanically deformed, and the piezoelectric effect of the quartz can be used to detect the electrical signal, thereby reversing the gas concentration. Under the same gas concentration and experimental conditions, the noise value will only fluctuate randomly in a small range, an...

AI Technical Summary

Problems solved by technology

However, if the laser power is too high, the thermal noise amplitude in the tuning fork will rise sharply, which will lead to the deterioration of the signal-to-noise ratio of the sensing system, and ultimately limit the detection performance of the sensor, making this method have great limitations.

Images