Composite optical microcavity of diamond nanopillar and silica microsphere

A composite optical microcavity, in which nitrogen vacancy (NV) centers in a diamond nanopillar are coupled to whispering gallery modes in a silica microsphere, is demonstrated. Nanopillars with a diameter as small as 200 nm are fabricated from a bulk diamond crystal by reactive ion etching and are positioned with nanometer precision near the equator of a silica microsphere. The composite nanopillar-microsphere system overcomes the poor controllability of a nanocrystal-based microcavity system and takes full advantage of the exceptional spin properties of NV centers and the ultrahigh quality factor of silica microspheres.