Abstract

Precise characterization of low loss, high reflectivity dielectric mirrors can be difficult with conventional techniques, such as FTIR and ring-down measurements. Ring-down measurements, ordinarily well suited to the characterization of low loss mirrors, are questionable when the reflectivity loss is smaller than intrinsic cavity losses. We have developed a technique for measuring the reflectivity of low loss dielectric mirrors that uses the intensity of light reflected from the cavity at resonance. Since the measurement is fundamentally an interference measurement between the wave reflected directly from the cavity mirror and the portion of the cavity field transmitted through the mirror, the technique is quite sensitive. Using a 12.7 m cavity and a 3.39 μm He-Ne laser, we have measured mirror losses as small as 0.01 % in a cavity with 0.3% intrinsic losses.

© 1992 Optical Society of America