New spectral features in an inhomogeneously broadened <i>N</i>-type four-level atomic system are analyzed and discussed. The atomic-level scheme uses an incoherent pumping rate in place of the incoherent recycling pump. We show that the gain profile includes an extra dip that appears only in the Doppler-broadened case. The dependence of this feature on various parameters, as well as consequences for the dispersion, are explored theoretically. For certain combinations of temperature and incoherent pump rate, this gain is shown to be independent of temperature fluctuations.
© 2000 Optical Society of America
W. H. Burkett, Yong-qing Li, and Min Xiao, "Inhomogeneous broadening-dependent spectral features in a four-level atomic system," J. Opt. Soc. Am. B 17, 293-299 (2000)