Observation of simultaneous fast and slow light
  We present a microresonator-based system capable of simultaneously producing time-advanced and time-delayed pulses. The effect is based on the combination of a sharp spectral feature with two orthogonally-polarized propagating waveguide modes. We include an experimental proof-of-concept implementation using a silica microsphere coupled to a tapered optical fiber and use a time-domain picture to interpret the observed delays. We also discuss potential applications for future all-optical networks. 
Pablo Bianucci, Chris R. Fietz, John W. Robertson, Gennady Shvets and   Chih-Kang Shih