Storage and retrieval of light pulses in atomic media with "slow" and   "fast" light
  We present experimental evidence that light storage, i.e. the controlled release of a light pulse by an atomic sample dependent on the past presence of a writing pulse, is not restricted to small group velocity media but can also occur in a negative group velocity medium. A simple physical picture applicable to both cases and previous light storage experiments is discussed. 
A. Lezama, A.M. Akulshin, A.I. Sidorov and P. Hannaford