Compression and collisions of chirped pulses in a dense two-level medium

摘要

Using numerical simulations, we study propagation of linearly-chirped opticalpulses in a homogeneously broadened two-level medium. We pay attention to thethree main topics -- validity of the rotating-wave approximation (RWA), pulsecompression, and collisions of counter-propagating pulses. The cases of longand single-cycle pulses are considered and compared with each other. We showthat the RWA does not give a correct description of chirped pulse interactionwith the medium. The compression of the chirp-free single-cycle pulse isstronger than of the chirped one, while the opposite is true for long pulses.We demonstrate that the influence of chirp on the collisions of the long pulsesallows to control the state of the transmitted radiation: the transmission ofthe chirp-free pulse can be dramatically changed under collision with thechirped counter-propagating one, in sharp contrast to the case when both pulsesare chirped. On the other hand, the collisions of the chirped single-cyclepulses can be used for precise control of medium excitation in a narrow spatialregion.