Study On High Reflectivity Measurement Method Based On Coupled Cavity Ring-down Technology

High reflectance measurement technology is the key technology of a variety of laser systems where a large number of high reflectance optical components are used.In order to obtain new breakthroughs in high reflectance coating technology,higher precision measurement technology is indispensable.Cavity ring-down technology is the only known method that can precisely measure reflectance greater than 99.9%.To solve the problem of introducing additional errors due to the conversion of the cavity structure during the application of the coupled cavity ring-down technology in the high reflectance measurement application,this thesis focuses on the cavity adjustment standard during the high reflectance measurement experiment based on this technology.Existing experimental results of coupled cavity ring-down technology in a straight cavity structure is introduced in this thesis.Considering the convenience of experiments and the need for intracavity mode analysis,V-cavity structure is proposed based on coupled cavity ring-down technology.By deriving the coupling efficiency theory of the V-cavity structure and establishing a simulation model,the factors affecting the coupling efficiency of this technology are obtained.By establishing a simulation model for high reflectance measurement,it is theoretically determined that the technology can improve the precision of high reflectance measurement based on traditional cavity ringdown technology.Based on the existing experimental conditions,the method of cavity adjustment combining "mode and formant" is introduced in detail.Through simulation analysis based on the intra-cavity mode,the factors affecting the morphology of the superimposed light spot in the coupled cavity are obtained.Then,through specific experimental analysis,the cavity adjustment method applied to the coupled cavity ringdown technology is finally determined,which provided a basis for cavity adjustment for the subsequent application of this technology to high reflectance measurement.The cavity loss relationship between the coupled cavity ring-down technology and the traditional cavity ring-down technology is analyzed,and the "fine tuning" standard for high reflectance measurements is obtained.Finally,the high-reflectance measurement experiment was carried out by combining the obtained cavity adjustment method and the "fine adjustment" standard.The experimental results show that the coupled cavity ring-down technology can achieve a relative improvement in measurement precision from 10.0% to 27.1% compared with the traditional cavity ringdown technology.This thesis mainly solves some problems in the application of coupled cavity ringdown technology in high reflectance measurement.For the application of coupled cavity ring-down technology in other fields,the research results of this thesis can also provide some reference.