Study of a four-level system in vee + ladder configuration

Abstract

We present the results of a theoretical study of a four-level atomic system in vee + ladder configuration using a density matrix analysis. The absorption and dispersion profiles are derived for a weak probe field and for varying strengths of the two strong control fields. For specificity, we choose energy levels of 87 Rb, and present results for both stationary atoms and moving atoms in room temperature vapor. An electromagnetically induced absorption (EIA) peak with negative dispersion is observed at zero probe detuning when the control fields have equal strengths, which switches to electromagnetically induced transparency (EIT) with positive dispersion (due to splitting of the EIA peak) when the control fields are unequal. There is significant linewidth narrowing in thermal vapor.

Sub- and super-luminal light propagation using a Rydberg state

“…For an atomic vapor at room temperature, we have to account for thermal velocity distribution by carrying out Doppler averaging, which is the typical condition used for an experimental realization. We consider an atom with velocity v interacting with co-propagating probe and switching fields, and a counter-propagating control field [13,14]. Since the wavelengths of probe and control fields are mismatched, the two photon absorption for the ladder sub-system is non-Doppler free, i.e.…”

All-Optical Switching In A Medium of A Four-Level Vee-Cascade Atomic Medium

“…Although all-optical switching in pulse mode have been studied for several four-level configurations but there still lacks study for the four-level V + Ξ system. As suggested by Bharti et al, [31], the four-level V + Ξ configuration could be actively switched between EIT and EIA modes. From the physics point of view, the medium of such behaviour is favourable to generate all-optical switching.…”

“…In addition to the three-level systems, EIT has also been implemented in four-level atomic systems including N-type (Λ+V) [26], inverted Y-type (Λ+Ξ) [27][28][29], tripod-type (Λ+Λ) [30] and V+Ξ-type [31] configurations. The advantage of four-level atomic systems is that it can be generated double-EIT windows and can be switched between EIT and EIA by signal field or external magnetic field.…”

Observation of electromagnetically induced absorption in a vee + ladder system

“…EIA has been reported in four level N type systems [14][15][16] with two control beams and one probe beam, in degenerate two level systems [17][18][19] and recently in a three level system [20]. Recently, we have theoretically proposed a new kind of four-level EIA system in a vee + ladder configuration [21]. Using this scheme, we have presented the first theoretical observations of Rydberg EIA [22] and tuning of the group velocity of light between sub-and superluminal propagation using a Rydberg state [23].…”