The Autler-Townes doublet in a pulse driven three-level system

When a two-level system is strongly driven on resonance by an incident field, its emission spectrum displays the well known Mollow triplet[1]. If on the hand the absorption from the excited state of this two-level system to a third, higher energy level, is probed, the resulting absorption spectrum features the Autler-Townes doublet[2]. It has been shown that when the two-level system is instead driven by a periodic pulse sequence, the emission spectrum obtained has strong similarities with the Mollow triplet[3]. It is then natural to ask: What is, in this case, the faith of the Autler-Townes doublet? We find that, for a three-level system in the "ladder" configuration, the absorption from the intermediate energy level to the upper level while the transition between the bottom and intermediate energy levels is driven by a periodic pulse sequence has a structure that is dictated by the pulse sequence. This is the case even when the pulse field is moderately detuned from the transition frequency. We discuss the model describing this system and present results for various system parameters.

[1] B. R. Mollow, Phys. Rev. 188, 1969 (1969).

[2] S. H. Autler and C. H. Townes, Phys. Rev. 100, 703 (1955).

[2] H. F. Fotso et al, Phys. Rev. Lett. 116, 033603 (2016).