Enhancement of microcavity lifetimes using highly dispersive materials
  We show analytically, and numerically that highly-dispersive media can be used to drastically increase lifetimes of high-Q microresonators. In such a resonator, lifetime is limited either by undesired coupling to radiation, or by intrinsic absorption of the constituent materials. The presence of dispersion weakens coupling to the undesired radiation modes and also effectively reduces the material absorption. 
Marin Soljacic, Elefterios Lidorikis, Lene Vestergaard Hau, J.D.   Joannopoulos