Effects of Temperature of Laser Shell on Background Signals for Trace Gas Detection in TDLAS
CHEN Hao1,2，JU Yu1，HAN Li1，LIU Jun-biao1
1. Institute of Electrical Engineering, Chinese Academy of Sciences, 100190 Beijing, China
2. University of Chinese Academy of Sciences, 100049 Beijing, China
Abstract：As the technique of tunable diode laser absorptionscopy (TDLAS) is employed for trace gas detection, the second-harmonic background signal drifts with the changeof the temperature of semiconductor laser shells. It results in unstability of the second-harmonic signal. Its drifting can cause measurement errors. Based on the principle of TDLAS, the cause of the second harmonic of the background signal is explained. Then the causes of the background signal and its drifting influence on measurement results are analyzed. In addition, the standard second-harmonic signal is obtained after the rejection of background signal. Finally a high-accuracy temperature control systemis designed and it is equipped with air cooling and water cooling modules for auxiliary temperature control. The control precision is between ±0.1 ℃. Moreover, 1 796 and 1 653 nm wavelength distrubuted feedback lasers are selected. By controlling the temperature of the two laser shells from 20 to 44 ℃ reversally, the temperature interval is 2 ℃, the experimental results of the second-harmonic background signal are studied. The test results indicate that: As the temperature of semiconductor laser shells rises, the background signal red-shifts; otherwise it blue-shifts. While testing the background signals of the 1 796 and 1 653 nm DFB lasers drift about 3.2 and 2.67 pm respectively at each temperature change of 2 degrees cenigrade. With the constant temperature control of semiconductor laser shells, it can effectively eliminate the influence of the background signal drifting when room temperature changes and enhance the stability of measurement system. The accuracy of trace gas detection is improved.
Key words：Gas detection; TDLAS; Background signal drift; Temperature characteristic
陈 昊，鞠 昱，韩 立，刘俊标. TDLAS痕量气体检测中激光器管壳温度对背景信号的影响[J]. 光谱学与光谱分析, 2018, 38(06): 1670-1674.
CHEN Hao，JU Yu，HAN Li，LIU Jun-biao. Effects of Temperature of Laser Shell on Background Signals for Trace Gas Detection in TDLAS. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2018, 38(06): 1670-1674.
