Femtosecond laser fabrication of high reflectivity micromirrors

High-quality freestanding micromirrors consisting of 40 dielectric layers on silicon have been fabricated by ultrashort-pulse laser ablation in combination with laser-assisted wet chemical etching. Backside material removal enables direct access to both faces of the dielectric coating. The amplitude reflectance of the micromirrors has been determined by Fabry-Peacuterot interferometry; a finesse in excess of 8900 +/- 700, corresponding to a reflectivity exceeding 99.95%, has been found. The mechanical quality factor, Q, of the microresonators, measured at 20 K, is determined to be between 5000 and 6000. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3467846]