A calibration-free cavity-enhanced absorption spectroscopy method for measuring reflectivity of an optical cavity

By extracting the phase information of reflected light through the detection system, the reflectivity of the optical cavity is directly measured and the gas concentration is inverted, which solves the problem of large reflectivity measurement error in the existing technology and realizes high sensitivity and high efficiency cavity-enhanced absorption spectroscopy measurement.

CN116735513BActive Publication Date: 2025-12-16CHANGCHUN INST OF OPTICS FINE MECHANICS & PHYSICS CHINESE ACAD OF SCI
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Patent Information

Application Number
CN202310960674.5
Authority / Receiving Office
CN · China
Patent Type
Patents(China)
Current Assignee / Owner
Filing Date
2023-08-01
Publication Date
2025-12-16
Estimated Expiration
2043-08-01

AI Technical Summary

Technical Problem

Existing technologies struggle to accurately measure the reflectivity of optical cavity mirrors, especially when the reflectivity is low. Furthermore, the standard gas method is susceptible to inaccurate gas concentration and laser intensity shifts, resulting in significant errors.

Method used

The phase information of the reflected light is extracted by the detection system to obtain the error signal. The reflectivity of the optical cavity is directly measured using the error signal. The concentration of the gas to be measured is obtained by cavity-enhanced absorption spectroscopy inversion, avoiding the standard gas calibration process. The detection system consists of a laser, an electro-optic modulator, a three-terminal circulator, a collimator, a mode-matching lens group, and a photodetector.

Benefits of technology

It enables accurate measurement of optical cavity reflectivity even at low reflectivity, avoiding errors introduced by inaccurate standard gas concentration and laser intensity shift, and features high sensitivity, high efficiency and convenience.

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Abstract

The present application relates to the technical field of optical gas sensing, and particularly relates to a kind of cavity enhanced absorption spectroscopy methods of calibration-free cavity reflectivity, comprising the following steps: S1: the phase information of reflected light is extracted by detection system and error signal is obtained, and the optical cavity reflectivity at the target absorption line of the gas to be measured is obtained by error signal;Detection system includes laser, electro-optic modulator, three-terminal circulator, collimator, mode matching lens group, optical cavity, photodetector one, function generator, frequency mixer, acquisition card and computer;S2: the gas to be measured is introduced into the optical cavity, and the cavity enhanced absorption spectrum of the gas to be measured is obtained;S3: the concentration of the gas to be measured is obtained by inversion using the determined optical cavity reflectivity and cavity enhanced absorption spectrum.The present application does not need additional standard gas, avoids the error introduced by the uncertainty of standard gas concentration, and also makes up for the deficiency that traditional optical cavity ring-down technique is difficult to measure reflectivity when reflectivity is relatively low.
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