Tunable Resonant Optical MicroCavities by Self-Assembled Templating
  Micron-scale optical cavities are produced using a combination of template sphere self-assembly and electrochemical growth. Transmission measurements of the tunable microcavities show sharp resonant modes with a Q-factor>300, and 25-fold local enhancement of light intensity. The presence of transverse optical modes confirms the lateral confinement of photons. Calculations show sub-micron mode volumes are feasible. The small mode volume of these microcavities promises to lead to a wide range of applications in microlasers, atom optics, quantum information, biophotonics and single molecule detection. 
G.V. Prakash, L. Besombes, T. Kelf, P.N. Bartlett, M.E. Abdelsalam,   J.J. Baumberg