Twofold light-pulse regeneration under conditions of electromagnetically induced transparency

This paper shows that it is theoretically possible for a medium to generate two copies of an incoming probe pulse as a result of the successive action of two control pulses under conditions of electromagnetically induced transparency. The medium is treated in the model of two-level atoms with threefold degeneration of the lower level (tripod configuration). The three laser-radiation pulses differ in polarization, and the propagation directions of the probe pulse and the two control pulses are orthogonal. The calculation uses a semiclassical approach, the slow-amplitude approximation, and the fixed-field approximation of the control pulses.