Coherent differential absorption laser radar and method for detecting gas concentration

Abstract

The invention provides a coherent differential absorption laser radar comprising a first tunable continuous wave laser, a second tunable continuous wave laser, a beam splitter, an acousto-optic modulator, a laser amplifier, a circulator, a transmitting and receiving telescope, a coupler, a balance detector, an acquisition card and a digital signal processing system. Two required laser wavelengthsare determined by selecting appropriate absorption lines of gas molecules to be tested in intermediate infrared, then local oscillation light and signal light are split by the beam splitter, frequencies are finally combined by the coupler, and the balance detector is used for detection to obtain a concentration of the gas molecules. Due to the larger gas absorption cross-section coefficient and lower background radiation of the intermediate infrared, the detection sensitivity is improved. The use of coherent detection instead of direct detection reduces the influence of low quantum efficiencyon the precision of detection, improves the utilization of echo signals, and improves the performance of the differential absorption laser radar.

Description

Technical field [0001] The present invention relates to the technical field of laser radar, in particular to a coherent differential absorption laser radar and a method for detecting gas concentration. Background technique [0002] Lidar technology has received widespread attention since the birth of lasers, and has been used in military, meteorological and atmospheric monitoring with its strong anti-interference ability and high precision. Lidars with different structures and different uses continue to emerge. Differential absorption radar is an important application of lidar. Currently, differential absorption radar is used in many aspects such as air pollutant monitoring. [0003] Most gas molecules have their own characteristic absorption lines, and the dark lines left in the spectrum due to the selective absorption of gas molecules are absorption lines. Differential absorption lidar detects atmospheric pollution by selecting the wavelength of the characteristic absorption li...

AI Technical Summary

Problems solved by technology

In the infrared band, due to the low quantum efficiency of photodetectors in existing materials, the application of direct detection in the mid-infrared band is limited.

Images