@article{3314, author = {Garrett Cole and W. Zhang and M. Martin and Jun Ye and Markus Aspelmeyer}, title = {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. Employing these ‘crystalline coatings’ as end mirrors in a Fabry–Pe´rot cavity, we obtain a finesse of 150,000. More importantly, at room temperature, we observe a thermally limited noise floor consistent with a tenfold reduction in mechanical damping when compared with the best dielectric multilayers. These results pave the way for the next generation of ultra-sensitive interferometers, as well as for new levels of laser stability.}, year = {2013}, journal = {Nature Photonics}, volume = {7}, pages = {644-650}, month = {2013-07}, issn = {1749-4885}, url = {http://www.nature.com/doifinder/10.1038/nphoton.2013.174}, doi = {10.1038/nphoton.2013.174}, }