A high-reflectivity high-Q micromechanical Bragg-mirror
  We report on the fabrication and characterization of a micromechanical oscillator consisting only of a free-standing dielectric Bragg mirror with high optical reflectivity and high mechanical quality. The fabrication technique is a hybrid approach involving laser ablation and dry etching. The mirror has a reflectivity of 99.6%, a mass of 400ng, and a mechanical quality factor Q of approximately 10^4. Using this micromirror in a Fabry Perot cavity, a finesse of 500 has been achieved. This is an important step towards designing tunable high-Q high-finesse cavities on chip. 
H.R. Boehm, S. Gigan, G. Langer, J. Hertzberg, F. Blaser, D. Baeuerle,   K. Schwab, A. Zeilinger and M. Aspelmeyer