Wavelength mismatch effect in electromagnetically induced absorption

Abstract

We present a theoretical investigation of the phenomenon of electromagnetically induced absorption (EIA) in a 4-level system consisting of vee and ladder subsystems. The four levels are coupled using one weak probe field, and two strong control fields. We consider an experimental realization using energy levels of Rb. This necessitates dealing with different conditions of wavelength mismatch---near-perfect match where all three wavelengths are approximately equal; partial mismatch where the wavelength of one control field is less than the other fields; and complete mismatch where all three wavelengths are unequal. We present probe absorption profiles with Doppler averaging at room temperature to account for experiments in a room temperature Rb vapor cell. Our analysis shows that EIA resonances can be studied using Rydberg states excited with diode lasers.Comment: 12 pages, 7 figure

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

“…In the absence of switching field (solid curve), the damped oscillations become steady and probe absorption reduces to zero [27]. Now, if the switching field is turned on-with Rabi frequency equal to control field-the enhanced probe absorption is observed (dashed curve) [14,28]. With further increase in switching Rabi frequency, the enhanced absorption again reduces close to zero (dotted curve).…”

“…Since the probe field is weak, it ensures that levels |e and |r are always unpopulated and population cycles between levels |g and |s . This level scheme has been utilized for the realization of EIA using a Rydberg state [14].…”

“…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.…”

“…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. k p v−k c v = 0, and probe absorption spreads over different velocity classes [14].…”

“…Furthermore, in contrast to our work in Ref. [14] where we study only Rydberg EIA, we concentrate here on the dispersion curve (its slope) and refractive index of the medium. We also present the transient response of our system, which shows that the medium can be used for absorptive optical switching.…”