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-Pérot cavity, a finesse of 500 has been achieved. This is an important step towards designing tunable high- Q high-finesse cavities on chip.