Design and fabrication of ultrahigh Q chip-based silica WGM micro-resonators for single-atom cavity-QED

Of the many applications of whispering-gallery-mode (WGM) micro-resonators, single-atom cavity quantum electrodynamics (cavity-QED) poses the most extreme demands on mode volume, dimensions, and quality factor ( Q ). Here we present the procedure for the fabrication of chip-based, small mode-volume, ultrahigh- Q silica WGM micro-resonators, designed for single-emitter cavity-QED. We demonstrate micro-resonators at varying geometries, from toroidal to micro-spheres, yielding ultrahigh-qualities as high as 1.7 × 10 8 at 780nm. We present a comprehensive theoretical model that allows tailoring the fabrication process to attain the desired micro-resonator geometry.