Design Of A Near Infrared Ammonia Gas Detection System Based On TDLAS Technology With VCSEL Laser

Ammonia?NH₃?is a corrosive,toxic and harmful industrial gas,which has a corrosive and irritating effect on skin tissues.It has great harm to air quality,environmental safety,human health,etc.Therefore,high-precision real-time monitoring of NH₃ concentration has a great promotion effect on maintaining environmental quality and improving living environment.Accurate early warning of disasters,industrial safety in production,and reduction of explosion accidents have important scientific and social significance.At present,the research and development of TDLAS laser gas detection technology generally adopts DFB laser as the detection light source.High power consumption and large volume are the characteristics of this technology solution,and the application of TDLAS detection technology in power sensitive places is limited.High efficiency,low power,and small size are the characteristics of VCSEL-type lasers.For power-sensitive applications,VCSEL lasers can effectively improve the power and volume issues of the entire system of TDLAS detection technology.In this thesis,with the support of the National Science and Technology Research Project of the Funding Committee—"Development of Miniaturized Universal TDLAS Gas Detection Modules Using VCSEL Core Laser Light Sources"?No.61727822?,this thesis analyzes TDLAS with VCSEL lasers as the core light source.The detection technology deduces the change process of the detection signal during the detection process,and provides a theoretical basis for the development of the NH₃ detection system.Based on the spectroscopy theory of gas absorption and VCSEL lasers'emission characteristics,the absorption line of NH₃ was selected.Aiming at the interference caused by the fluctuation of the laser in the single optical path detection system,a time division multiplexing differential modulation technique is proposed,which can further eliminate the interference caused by the laser light intensity fluctuation in the single optical path detection system.Based on the TDLAS gas concentration detection theory and the luminescent characteristics of VCSEL lasers,this thesis carried out a software simulation of the NH₃detection process.A VCSEL laser suitable for this system was selected,a small current drive circuit was developed,and the overall design of the detection system and the construction of the experimental platform were completed in combination with a photodetector and a lock-in amplifier.In this thesis,the detection system developed is used for NH₃ gas concentration detection test.Based on the second harmonic data extracted by the lock-in amplifier,various performance indicators of the system are analyzed and conclusions are drawn.