Low-noise meta-mirrors in optical cavities - current status and prospects

The precision of many applications in high-precision metrology involving optical cavities is limited by the Brownian thermal noise of mirror coatings. Meta-mirrors are promising to overcome current noise limitations. In this contribution, we demonstrate a meta-etalon combining a meta-mirror with a conventional multilayer mirror to enhance the maximum reflectivity of the meta-mirror while maintaining low thermal noise. By this, we achieve a cavity finesse of 11.500, more than a factor of 10 larger than the maximum achieved with standalone meta-mirrors.