Europhys. Lett.
Volume 63, Number 1, July 2003
Page(s) 35 - 41
Section Electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics
Published online 01 June 2003
DOI: 10.1209/epl/i2003-00474-0
Europhys. Lett., 63 (1) , pp. 35-41 (2003)

Collapse and revival of a Dicke-type coherent narrowing in a sub-micron thick vapor cell transmission spectroscopy

G. Dutier1, A. Yarovitski1, S. Saltiel1, A. Papoyan2, D. Sarkisyan2, D. Bloch1 and M. Ducloy1

1  Laboratoire de Physique des Lasers, UMR 7538 du CNRS Université Paris 13 - 99 Av J.-B. Clément, 93430 Villetaneuse, France
2  Institute for Physical Research, Armenian Academy of Sciences Ashtarak 2, 378410 Armenia

(Received 10 March 2003; accepted 2 May 2003)

In a thin cell of dilute vapour, the absorption spectrum exhibits sub-Doppler features due to the relative enhancement of the slow atom contribution, with respect to the transient nature of the interaction with moving atoms. For a two-level system in the linear regime, the narrowest response is predicted to be found for a $\lambda/2$ thickness, as an effect of the coherent character of the dipole response as early described by Romer and Dicke (Phys. Rev., 99 (1955) 532) in the microwave regime. We report here on the direct observation of this effect in the optical regime in an ultra-thin vapour cell. This effect is shown to vanish for a thickness equal to $\lambda$, and a revival is observed at $3\lambda/2$, as expected from the predicted $\lambda$-periodicity. The experiment is performed on the D1 resonance line of $\chem{Cs}$ vapour ( $\lambda=894$ $\un{nm}$), in a specially designed cell, whose thickness varies locally.

42.50.Gy - Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption.
32.70.Jz - Line shapes, widths, and shifts.
42.50.Md - Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency.

© EDP Sciences 2003