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.
KEYWORDS: Signal attenuation, Signal processing, Signal detection, Time metrology, Data acquisition, Computing systems, Fourier transforms, Signal to noise ratio, Thin films, Spectroscopy
As a parameter of the process of an event, the measurement of decay time constant has been widely used in many fields such as electronic information, economy, chemistry and biology. How to quickly and accurately obtain the decay time constant of various kinds of decay signals has always been a hot issue in the field of testing technology. In this paper, research and carding are carried out on the fast and accurate decay acquisition method of time constant of single exponential decay signal. The main purpose is to comprehensively grasp the main methods adopted in current engineering technology and scientific research, and on this basis, a set of fast and accurate acquisition scheme of attenuation time constant based on ZYNQ system is proposed, It lays a foundation for the development of cavity ring down loss measurement and spectrum measurement system.
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