Influence of atomic densities on propagation property for ultrashort pulses in a two-level medium

The influence of atomic densities on the propagation property for ultrashort pulses in a two-level atom (TLA) medium is investigated. With higher atomic densities, the self-induced transparency (SIT) cannot be recovered even for 2πultrashort pulses. New features such as pulse splitting, red-shift and blue-shift of the corresponding spectra arise, and the component of central frequency gradually disappears.     

Spectral Effects for an Ultrashort Pulse Train Propagating in a Two-Level Atom Medium

We investigate the spectra of a femtosecond pulse train propagating in a resonant two-level atom (TLA) medium.It is found that higher spectral components can be produced even for a 2π femtosecond pulse train. Furthermore,the spectral effects depend crucially on both the relative shift Ф and the delay time τ between the successive pulses of the femtosecond pulse train.