Efficiency of light-frequency conversion in an atomic ensemble
  The efficiency of frequency up and down conversion of light in an atomic ensemble, with a diamond level configuration, is analyzed theoretically. The conditions of pump field intensities and detunings required to maximize the conversion as a function of optical thickness of the ensemble are determined. The influence of the probe pulse duration on the conversion efficiency is investigated by numeric solution of the Maxwell-Bloch equations. 
H. H. Jen and T. A. B. Kennedy
quant-ph