The Measurement Of Reflectivity Based On Supercontinuum Cavity Ring-down Spectroscopy

In recent years,the rapid development of optical coating technology and the widely application of low loss and high-reflectivity(>99.9%)elements make it more and more urgent to measure the reflectivity of reflective devices accurately.Traditional reflectivity measurement techniques,such as multiple reflection method and the light transmission method,cannot meet the requirements,and cavity ring-down spectroscopy is generally considered to be a good method for accurate measurement of high reflectivity which can be higher than 99.99%.But the traditional CRDS technology has a certain limitation,people launched an investigation by using the supercontinuum light source as its input light source.Based on the principle of cavity ring-down spectroscopy,first,we discussed the advantages and disadvantages of traditional CRDS technique for high reflectivity measurement.Internationally,we first proposed a new scheme for measuring the reflectivity of high-reflectivity mirror by using femtosecond laser generated supercontinuum radiation as the probe source of supercontinuum cavity ring-down spectroscopy technology.The supercontinuum cavity ring-down spectroscopy detection system for 630-730 nm and 750-790 nm was constructed by femtosecond laser,supercontinuum radiation generation system,ring-down cavity and PI spectrometer coupled with ICCD.The 400-450 nm supercontinuum cavity ring-down spectroscopy detection system was constructed by femtosecond laser,BBO crystal and so on.Then,using two kinds of experimental devices: straight cavity type and folded cavity type,the reflectivity of different mirrors was measured.The reflectivity calculation program was compiled by Mathematica,the reflectivity of the cavity mirrors and the high-reflectivity mirrors of different material at different wavelength were obtained.The reflectivity curve of near 100 nm was obtained.Finally,the cause of experimental error was discussed.In this paper,an efficient and accurate method was detail checked by the experiment.The work done in this thesis is a great significance to the development of measuring the reflectivity of high-reflectivity mirror.