This technique mainly uses the characteristics of narrow linewidth and wavelength of tunable semiconductor lasers varying with injection current to measure single or several absorption lines of molecules which are very close to each other and are difficult to distinguish.

Tunable semiconductor lasers, commonly used in TDLAS technology, include Fabry-Perot lasers, Distributed Feedback lasers, Distributed Bragg reflector lasers, Vertical-cavity surface-emitting lasers and external-cavity tunable semiconductor lasers. Light apparatus.

TDLAS usually scans an independent gas absorption line with a single narrowband laser frequency. In order to achieve the highest selectivity, the analysis is usually carried out at low pressure, at which time the absorption line will not be broadened due to pressure. This method was proposed by Hinkley and Reid, and has now developed into a very sensitive and commonly used monitoring technology for trace gases in the atmosphere.

(1) High selectivity and high resolution spectroscopy is not interfered by other gases because of the "fingerprint" feature of molecular spectroscopy. This characteristic has obvious advantages over other methods.

(2) It is a general technology that is effective for all the active molecules absorbed in infrared. The same instrument can be easily changed into an instrument for measuring other components, only changing the laser and standard gas. Because of this characteristic, it is easy to change it into a simultaneous multi-component measuring instrument.

(3) It has the advantages of fast speed and high sensitivity. Without losing its sensitivity, its time resolution can be in MS magnitude. The main application fields of this technology include: molecular spectroscopy, industrial process monitoring and control, combustion process diagnosis and analysis, engine efficiency and motor vehicle exhaust measurement, explosion detection, trace pollution gas monitoring in the atmosphere, etc.

(1) Obtaining information about molecular structure;

(2) Studying the dynamic process;

(3) Gas monitoring and analysis.