Transmission spectroscopy in an ultrathin vapor cell, which has been recently demonstrated as a new method of sub-Doppler spectroscopy in the optical domain, is revisited. We show that, because of an unavoidable Fabry-Perot effect, the observed signal-in transmission spectroscopy and selective reflection spectroscopy as well-is actually an interferometric mixture of the optical responses as provided in transmission and in reflection by a long macroscopic cell. After the derivation of a very general solution, we restrict ourselves to the case of a linear interaction with the resonant laser. We finally discuss the application to a two-level atom for which analytical expressions are given, in the large Doppler limit, for FM transmission and reflection signals.

PACS. 42.50.Gy -Effects of atomic coherence on propagation, absorption, and amplification of light; electromagnetically induced transparency and absorption. PACS. 32.70.Jz -Line shapes, widths, and shifts. PACS. 42.50.Md -Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency.Abstract.-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 λ/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 λ, and a revival is observed at 3λ/2, as expected from the predicted λ-periodicity. The experiment is performed on the D1 resonance line of Cs vapour (λ = 894 nm), in a specially designed cell, whose thickness varies locally.

A microfabricated Fabry-Perot optical resonator has been used for atom detection and photon production with less than 1 atom on average in the cavity mode. Our cavity design combines the intrinsic scalability of microfabrication processes with direct coupling of the cavity field to singlemode optical waveguides or fibers. The presence of the atom is seen through changes in both the intensity and the noise characteristics of probe light reflected from the cavity input mirror. An excitation laser passing transversely through the cavity triggers photon emission into the cavity mode and hence into the single-mode fiber. These are first steps towards building an optical microcavity network on an atom chip for applications in quantum information processing.PACS numbers: 42.50. Pq, 03.67.Lx, 03.75.Be When a neutral atom is placed in a high-finesse optical cavity, the electric dipole coupling between the atom and the light field can lead to quantum coherence between the two. This fact forms the basis of cavity quantum electrodynamics (QED) [1]. Recently, there has been considerable interest in the possibility of applying cavity QED to problems in quantum information processing, as reviewed, for example, in Ref. [2]. Single photons have been generated on demand from falling [3] and trapped [4] atoms in high-finesse Fabry-Perot cavities, and recent experiments have investigated the cavityassisted generation of single photons from atomic ensembles [5]. These are important steps towards building multiple-cavity quantum information networks, such as those proposed in Ref. [6]. However, experiments so far have been limited to single cavities by the technical demands of achieving high enough finesse. Outstanding challenges now are to make the cavities smaller, to fabricate them in large numbers with the possibility of multiple interconnects, and to load them conveniently and deterministically with atoms. This would pave the way to circuit-model quantum computers [7], to one-way computations based on cluster states [8], and to other schemes requiring multiple cavities [9].As a first move in this direction, two recent experiments have used a small magnetic guide to load atoms into a cavity [10]. However the cavities in these experiments were 2-3 cm long and therefore not more scalable than a conventional Fabry-Perot cavity. By contrast, Aoki et al. have dropped atoms close to a microscopic toroidal cavity and observed evidence of strong coupling [11]. These resonators can be microfabricated in large arrays, however they are not easily used for controlled atom-cavity coupling because of the need to position the atom very precisely in the evanescent field just outside the surface of the resonator. For this reason it is of interest to consider microscopic Fabry-Perot cavities, whose open structure gives access to the central part of the cavity field. In one recent design [12], the two mirrors of such a resonator are formed by optical fibers whose tips have been modified into concave reflectors. This design can achieve small mode...

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We consider the extension of optical metamaterials to matter waves and then the down scaling of metaoptics to nanometric wavelengths. We show that the generic property of pulsed comoving magnetic fields allows us to fashion the wave-number dependence of the atomic phase shift. It can be used to produce a transient negative group velocity of an atomic wave packet, which results into a negative refraction of the matter wave. Application to slow metastable argon atoms Ar(3P2) shows that the device is able to operate either as an efficient beam splitter or an atomic metalens.

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The distance-dependence of the anisotropic atom-wall interaction is studied. The central result is the 1/z 6 quadrupolar anisotropy decay in the retarded Casimir-Polder regime. Analysis of the transition region between non-retarded van der Waals regime (in 1/z 3 ) and Casimir-Polder regime shows that the anisotropy cross-over occurs at very short distances from the surface, on the order of 0.03λ, where λ is the atom characteristic wavelength. Possible experimental verifications of this distance dependence are discussed. PACS numbers: 34.35.+a, 03.75.Be, 12.20.Fv The force between neutral polarisable systems is a ubiquitous phenomenon in nature, with many applications in physics, chemistry, biology. . . A paramount example is the long-range interaction potential between neutral microscopic quantum systems, like atomic systems, and a solid surface. For plane surfaces this interaction is usually governed by a power-law attractive potential [1,2]. For atom-surfaces distances z smaller than the wavelengths of the optical transitions involved in the atomic polarisability, the interaction is of the dipoleinduced dipole type, and governed by the well-known non-retarded van der Waals potential in −C 3 /z 3 , which reflects the correlations of dipole fluctuations [1]. At larger distances, retardation effects get important, and asymptotically lead to a −C 4 /z 4 potential, as demonstrated in the pioneering work of Casimir and Polder [2].Atom (molecule) -surface forces are central in numerous scientific and technological domains: surface adsorption of atoms, gas-surface equilibrium, cavity QED [3], quantum reflection of atoms on surfaces [4], microelectromechanical systems [5], research for a fifth fundamental force [6], etc. In most of the above studies, the interaction potential has to be treated in its full distance range (retarded and non-retarded), but is generally considered scalar. However the atom-surface potential has a cylindrical symmetry around the surface normal, and exhibits a quadrupolar component which may get important for non-scalar energy levels. Anisotropic surface potential strongly alters the internal dynamics and symmetry of nearby atomic systems. For example, surfaceinduced symmetry break and internal level coupling have been observed on rare-gas metastable states scattered at material surfaces [7]. From previous experimental studies of the anisotropic potential, on can underline two points: (i) on one hand, in selective reflection (SR) studies -generally sensitive to a λ/2π distance (∼ 100 nm) * Corresponding author: martial.ducloy@univ-paris13.fr from the surface (see e.g.[8]) -, the influence of the anisotropic potential has not been observed, although SR spectroscopy gives access to the excited atomic response [9]; (ii) on the other hand, in beam scattering studies, the range of the anisotropic interaction appears to be always smaller than 10 nm -in general 5 nm or less - [10]. Thus one can state that up to now those anisotropic characteristics have been observed in the non-retarded regime. Ind...