Effects of Doppler broadening on Autler-Townes splitting in six-wave mixing

Abstract

The effects of Doppler broadening on Autler-Townes (AT) splitting in six-wave mixing (SWM) are investigated by the dressed-state model. We analyze the velocities at which the atoms are in resonance with the dressed states through Doppler frequency shifting and find that, depending on the wave-number ratio, there may be two resonant velocities which can originate from resonance with one of the dressed states or from resonance with two different dressed states. Based on this model, we discuss a novel type of AT doublet in the SWM spectrum, where macroscopic effects play an important role. Specifically, the existence of resonant peaks requires polarization interference between atoms of different velocities in addition to a change in the number of resonant atoms involved. Our model can also be employed to analyze electromagnetically induced transparency resonance and other types of Doppler-free high-resolution AT spectroscopy.

Macroscopic effects in electromagnetically-induced transparency in a Doppler-broadened system

“…3 in Ref. [27], when ζ 2 < 1, the velocities v + and v − originate from the resonances of the dressed states |+ and |− , respectively. By contrast, we have both v + and v − from the same dressed states when ζ 2 > 1.…”

“…In Ref. [27], we have analyzed the resonant velocities v ± at which the atoms are in resonance with the dressed states through Doppler frequency shifting. As shown in Fig.…”

“…In contrast to the case of ζ 2 > 1, here the velocities v + and v − originate from the resonances of the dressed states |+ and |− , respectively. [27] Since there are always atoms of velocities v = v + and v = v − which are in resonance with the dressed state and so contribute to the nonlinear polarization, the spectrum exhibits a characteristic of Doppler broadening, as shown in Fig. 4.…”

“…Physically, EIT is closely related to the Autler-Townes (AT) effect, [24] where dressed states are probed through a transition to or from a third level as a doublet excitation spectrum. Previously, we studied AT splitting in EIT-based six-wave mixing (SWM) in a Doppler-broadened system; [25][26][27] the effects of Doppler broadening on the splitting were explained by a dressed-state model, whereby we analyze the velocities at which the atoms become resonant with the dressed states through Doppler frequency shifting. Based on this dressedstate model, in this paper we shall study the EIT in a Dopplerbroadened cascaded three-level system.…”

Effect of residual Doppler averaging on the probe absorption in cascade type system: A comparative study

“…Effects of the very strong control field as well as its detuning on the probe absorption profile were shown in that article. Niu et al [30] investigated the effect of Doppler broadening on Autler-Towns splitting [26] in six-wave mixing in a cascade four-level system as well as a folded four-level system. Three different resonant fields were applied to the systems concerned.…”