Iterative Refinement of Arbitrary Micro-Optical Surfaces*

Optical cavities are highly sensitive, versatile, and well-suited for use in ultra-fine metrology.  Micro Fabry-Perot cavities can be realized using mirrors formed into the ends of optical fibers, which can then be integrated into atom-chip based magnetic traps to enable enhanced atom-photon coupling for nondestructive detection and in-situ optical manipulations of magnetically trapped atoms. We present our current advancements in custom milling of fiber surfaces with high precision.  We have demonstrated an agile iterative milling technique which integrates phase-shifting optical profilometry, a six-axis precision motion control stage, and a high-powered CO2 laser to ablate near arbitrary surface geometries on a variety of materials with dramatically reduced optimization time and resources.  To date, we have successfully formed concave mirrors with 1-3 nm root mean square error as compared to an exact spherical surface for a radius of curvature of 1mm on both fused silica and GRIN fibers, as well as modeled planar arrays of closely positioned cavities on a fused silica optical flat.