A scheme for trace gas detection using infrared optical feedback cavity enhanced spectroscopy

Cavity enhanced absorption spectroscopy (CEAS) technology is one of the new types laser absorption spectroscopy technique with high sensitivity and relatively simple detection principle, which is developing rapidly and becoming more and more popular in the field of trace gas detection. A scheme of high sensitivity infrared optical feedback cavity enhanced absorption spectroscopy system is established, based on the high quality optical passive resonator made of ultralow expansion coefficient glass-ceramics, combined with the optical feedback effect of semiconductor laser which can narrow the output laser linewidth and stabilize the laser frequency. The spectral scanning of the system is realized by simultaneously scanning the cavity length of the resonator and tuning the laser current, and the spectral resolution of 0.003 cm-1 and the noise equivalent absorption sensitivity are better than 2×10-9 cm-1Hz-1/2. The system is expected to be applied to real-time analysis of respiratory gas and realize the application of the technology in human breath diagnosis.