Experimental Evidence for Compensation of Doppler Broadening by Light Shifts

Abstract

The possibility of compensating Doppler broadening of spectral lines by velocity-dependent light shifts 1 " 3 is illustrated with the following example of a three-level system a-b-c [Fig c l(a)] 0 Suppose that one analyzes the spectral profile of the light emitted by atoms excited in level c (for example, by a discharge) around the frequency o> 0 ' of the transition c-a* Simultaneously, the atomic vapor is irradiated by an intense single-mode laser beam, with frequency co x close to the frequency co 0 of the transition b-a. For an atom moving with velocity v in the laboratory frame [ Fig, 1(b)], the laser frequency in its rest frame [ Fig. 1(c)] is Doppler shifted from oo L to Q L = u) L (1 + v/c). The laser radiation perturbs the energy levels of such an atom, inducing "light shifts" 4 which depend not only on the laser intensity, but also on the detuning of the apparent laser frequency G> L , seen by the atom in its rest frame, from the atomic frequency. Since cD L is 4

Three-photon electromagnetically induced transparency using Rydberg states

“…3 (d-f). This occurs because the Doppler shifts of the atoms are compensated by AC Stark shifts [18]. The theoretical fit curves in Fig.…”

Recovering the Homogeneous Absorption of Inhomogeneous Media

“…It was originally suggested by Cohen-Tannoudji et al that velocity-dependent light-shifts due to an additional field can be utilized to counteract the broadening due to the Doppler effect. This idea has been analyzed [26,27] and realized [28,29] in several configurations. Inhomogeneous light-shifts were also used for generating narrow features with multi-photon excitations of hot Rydberg atoms [9], and for increasing the coherence time of laser-trapped atoms [30].…”

“…Inhomogeneous light-shifts were also used for generating narrow features with multi-photon excitations of hot Rydberg atoms [9], and for increasing the coherence time of laser-trapped atoms [30]. Several proposals focused on counteracting the decrease in amplitude due to the inhomogeneity [27,28,31]. However, and despite its importance, no significant enhancement of the effective absorption crosssection has been experimentally realized so far.…”

Power narrowing: counteracting Doppler broadening in two-color transitions

“…For instance, the coherence time of collective excitations in atomic gasses is often limited by Doppler dephasing, hindering the performance of single-photon sources and memories [7-9]. As Doppler broadening is an inhomogeneous dephasing mechanism, one can potentially counteract it by introducing additional velocity-dependent shifts [10][11][12][13][14]. Here we study the counteraction of Doppler broadening by velocity dependent light-shifts and identify an important class of systems where such counteraction occurs naturally, without a need for additional auxiliary fields.Coherent two-photon processes, such as Raman transitions, two-photon absorption, and electromagnetically induced transparency (EIT), are at the heart of many quantum-optics protocols, ranging from quantum light sources and memories [15][16][17][18] to sensing and quantum nonlinear optics [19].…”