Modulation role of spontaneously generated coherence in the light fields propagating

By using the numerical calculation results of the density matrix equations of motion of a closed A-type inversionless lasing system, the effects of the propagation of light fields on the gain of lasing without inversion (LWI), Rabi frequencies of the probe and driving fields, and the modulation role of spontaneously generated coherence (SGC) on the effects were investigated when the Doppler broadening presents. It was shown that, with the distance increasing, LWI gain first increases and then decreases, Rabi frequency of the probe field (the driving field) increases monotonously (decreases); at a specific propagation distance, LWI gain first increases and then decreases with increasing of the Rabi frequency of the driving field at the entrance of the medium, and LWI gain decreases monotonously with increasing of the Doppler broadening width; SGC has a remarkable manipulation role on the effect of propagation of the light fields, the LWI gain with SGC is much larger than that without SGC.