Submicrometer diameter micropillar cavities with high quality factor and ultrasmall mode volume.

We theoretically demonstrate high quality factor (Q approximately 3x10(6)) micropillar cavities with a record low mode volume [V approximately 0.1(lambda/n)3] based on the TiO2/SiO2 material system. The proposed cavities have Q/V that is 3 orders of magnitude larger than previously reported ones. We show that our cavity embedded with a diamond nanocrystal provides a feasible platform for cavity quantum electrodynamics experiments in the strong coupling limit.