High reflectivity high-Q micromechanical Bragg mirror

The authors report on the fabrication and characterization of a micromechanical oscillator consisting only of a freestanding 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 400 ng, 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.