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 nonlinear 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.

中文翻译：

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使用腔衰荡技术精确测量超高反射率

由于缺乏“已知”校准样品和合格且有效的交叉验证方法，使用腔衰荡 (CRD) 技术精确测量绝对高，尤其是超高反射率 (R>99.999%) 的高反射镜具有挑战性. 本文通过滤除开路衰荡腔内光路中大粒子干涉引起的随机光损耗波动，大大提高了超高反射率的测量精度。超高反射率的绝对测量是通过对固定腔长和可变腔长CRD测量的反射率结果以及线性和非线性数据处理方法进行交叉检查来实现的。使用开放路径 CRD 实验设置，