Tunable diode laser absorption spectroscopy for sensing CO and CO2 of vehicle emissions based on temperature tuning

As the main species of vehicle emissions which are thought to be the most important reason of air pollutions in urban areas, CO and CO₂ have been detected by tunable diode laser absorption spectroscopy widely in recent years. In the method of current tuning, contiguous absorption peaks of CO and CO₂ are usually selected to detect their concentrations simultaneously which may lead to the mutual interference of their second harmonic signals by influence of the laser emission linewidth. As changing the temperature setting of the laser diode to detect target gas in a certain wavelength, the long adjustment process and the complex operating do not meet the requirement of fast real-time detection. According to this problems, a temperature tuning method of broad spectrum was proposed in this paper by controlling the thermoelectric cooler in laser, a 4nm tuning range of 1580nm DFB laser including multiple absorption peaks of CO and CO₂ was obtained for gas sensing and elimination of the inteference cuased by system and environment reasons. The method of temperature tuning shows its advantages by more detecting information, fast response speed, and low devices demands. It is suitable for situ sensing of vehicle emissions such as CO and CO₂.