Multi-type gas concentration measurement with cavity ring-down

Abstract

Cavity ring-down laser absorption spectroscopy is a sensitive, accurate way to acquire weak optical absorption spectra. The ring-down time is independent of light intensity, as is typical in most other forms of laser spectroscopy. According to the law of Beer-Lambert, the new continuous wave laser gas concentration measurement system based on the cavity ring-down is introduced. The ring-down time-gas absorption coefficient-gas concentration relation and the loop loss-gas absorption coefficient-gas concentration relation are analyzed and the measuring model is established. Avoid the aerosol scatter and Rayleigh scatter affect the measuring results. Accept nonlinear differential tunable laser source to increase the tuning range. Then, the ring-down times of three certain lights in three corresponding gases with the same concentration were obtained, and the gas absorption characteristics in different concentrations are given. The research proofs that the cavity ring-down based on nonlinear difference frequency theory is an effective method for trace gas measurement and analysis.