Time-dependent aspects of the Autler-Townes effect in a four-level system

Time-dependent optical Autler-Townes spectra are calculated for a four-level system in which the ground state is a doublet with frequency separation much larger than any of the Rabi frequencies. The finite linewidths of the lasers are taken into account in the phase-diffusion model. Optical-pumping effects cause a transfer of population with a resulting significant change in the spectra with time. Numerically evaluated spectra are presented, and it is found that the nature of the asymmetry can change drastically with time.