Superradiance of an extended resonant medium excited by half-cycle attosecond pulses

Here we demonstrate an unusual type of superradiance in an extended layer of a two-level medium excited by a pair of unipolar pulses. It is shown that, due to the interference of secondary waves emitted by the resonant medium, the response of such a layer in reflection represents a pair of half-cycle unipolar pulses of different polarity. They follow with a time delay proportional to the layer thickness. The source of such superradiance is a monopolar half-cycle pulse of the stopped polarization induced by the first excitation pulse and switched off by the second excitation pulse. The predicted effect can be used to control the shape of few- and subcycle pulses in resonant media.