Tenfold reduction of Brownian noise in high-reflectivity optical coatings

Abstract

Thermally induced fluctuations impose a fundamental limit on precision measurement. In optical interferometry, the current bounds of stability and sensitivity are dictated by the excess mechanical damping of the high-reflectivity coatings that comprise the cavity end mirrors. Over the last decade, the dissipation of these amorphous multilayer reflectors has at best been reduced by a factor of two. Here, we demonstrate a new paradigm in optical coating technology based on directbonded monocrystalline multilayers, which exhibit both intrinsically low mechanical loss and high optical quality.