Analysis of reflectivity measurement by cavity ring-down spectroscopy

This paper presents the experimental method to measure the high reflectivity of optical mirror by cavity ring-down spectroscopy. The experimental system uses a straight cavity composed of a pair of cavity mirrors with same reflectivity or a folded cavity which is formed from the straight cavity to be folded at 22.5° angle, a reflector is laid at folded point.The reflectivity of the cavity mirrors is measured to be（99.925±0.001）% and the reflector to be (99.992±0.003)％．The metrical precision achieves 10－5.The low loss and high reflectivity mirrors can be measured accurately by this setup．