Decay time in a cavity in slow or fast light regime

The authors present measurements of the decay time of the cavity for different group delays in the cell inside the cavity. The authors show that the group velocity rules the decay time of the cavity in case of positive dispersion: the authors obtained, for example, a decay time of 6.3 μs while the time response of the set-up (measured with the empty cavity) is only 0.4 μs. It is also possible with the set-up to go from a slow-light to a fast-light regime and even to a negative group velocity.