Etching techniques for realizing optical micro-cavity atom traps on silicon

We have fabricated curved optical micromirrors on silicon. We expect to be able to form open optical cavities between these mirrors and plane mirrors coated on the ends of optical fibres. The curved mirror templates have been prepared with less than 10 nm surface roughness by means of isotropic chemical etching. Two different methods are used for the fabrication of the mirrors: the first method uses a silicon oxide mask, while the second uses dry etching to form an indentation in the silicon surface that is opened out by wet isotropic etching. After coating the silicon substrate with gold, good quality mirrors are obtained with R similar to 98% in the near infra-red. We find that a reflectivity of approximately 98% can be achieved by this method. Cavities formed from these mirrors will be useful for manipulating single atoms.