Precise measurements of super-high reflectance with cavity ring-down technique

Abstract

The precise measurements of absolute high, especially super-high reflectances (R > 99.999%) of highly reflective mirrors with cavity ring-down (CRD) technique is challenging due to lack of ‘known’ calibration samples and eligible and effective cross-validation method. In this paper, measurement precision of super-high reflectance is greatly improved via filtering out the random optical loss fluctuation caused by large particle intervention in the beam path inside the open-path ring-down cavity. The absolute measurement of super-high reflectance is realized through cross-checking the reflectance results measured with fixed cavity length as well as variable cavity length CRDs together with linear and non-linear data processing approaches. With an open-path CRD experimental setup, the absolute reflectance of a highly reflective mirror for laser gyroscope is determined to be 99.99956% with an uncertainty of only approximately 0.2ppm.