109 research outputs found
Spectroscopy in Extremely Thin Vapor Cells : Sensitivity Issues
This communication focuses on sensitivity issues - a long-time concern of J.
Hall- in the spectroscopic analysis of Extremely Thin Cell of dilute vapor.
With these small and often submicrometric slices of vapor, the most uncommon
features are the relatively small number of interacting atoms, and the fact
that essential results are already obtained in the frame of linear
spectroscopy.Comment: Proceedings of the John Hall symposium (2005) to appea
Atom-Wall interaction
This chapter deals with atom-wall interaction occurring in the "long-range"
regime (typical distances: 1-1000 nm), when the electromagnetic fluctuations of
an isolated atom are modified by the vicinity with a surface. Various regimes
of interaction are discussed in an Introductory part, from Cavity Quantum
ElectroDynamics modifications of the spontaneous emission, to Casimir effect,
with emphasis on the atom-surface van der Waals interaction, characterized as a
near-field interaction governed by a z-3 dependence. The major part of the
Chapter focuses on the experimental measurements of this van der Waals
interaction, reviewing various recent techniques, and insists upon optical
techniques, and notably selective reflection spectroscopy which is particularly
well-suited when excited atoms are considered. A review of various experiments
illustrates the specific effects associated with a resonant coupling between
the atomic excitation and surface modes, from van der Waals repulsion to
surface-induced resonant transfer, and with anisotropy effects, including
metastability transfer induced by a quadrupole contribution in the interaction.
The effects of a thermal excitation of the surface -with a possible remote
energy transfer to an atom-, and of interaction with nanobodies -which are
intrinsically non planar- are notably discussed among the prospects.Comment: \`{a} paraitre dans : Advances in Atomic Molecular and Optical
Physics, vol.50, B. Bederson and H. Walther eds., Academic Pres
Doppler-free approach to optical pumping dynamics in the electric quadrupole transition of Cesium vapor
The electric quadrupole transition is investigated in
Cesium vapor at room temperature via nonlinear Doppler-free 6P-6S-5D
three-level spectroscopy. Frequency-resolved studies of individual E2 hyperfine
lines allow one to analyze optical pumping dynamics, polarization selection
rules and line intensities. It opens the way to studies of transfer of light
orbital angular momentum to atoms, and the influence of metamaterials on E2
line spectra.Comment: 4 pages, 5 figures, minor updates from previous versio
Tailoring optical metamaterials to tune the atom-surface Casimir-Polder interaction
Metamaterials are fascinating tools that can structure not only surface
plasmons and electromagnetic waves but also electromagnetic vacuum
fluctuations. The possibility of shaping the quantum vacuum is a powerful
concept that ultimately allows engineering the interaction between macroscopic
surfaces and quantum emitters such as atoms, molecules or quantum dots. The
long-range atom-surface interaction, known as Casimir-Polder interaction, is of
fundamental importance in quantum electrodynamics but also attracts a
significant interest for platforms that interface atoms with nanophotonic
devices. Here we perform a spectroscopic selective reflection measurement of
the Casimir-Polder interaction between a Cs(6P_{3/2}) atom and a nanostructured
metallic planar metamaterial. We show that by engineering the near-field
plasmonic resonances of the metamaterial, we can successfully tune the
Casimir-Polder interaction, demonstrating both a strong enhancement and
reduction with respect to its non-resonant value. We also show an enhancement
of the atomic spontaneous emission rate due to its coupling with the evanescent
modes of the nanostructure. Probing excited state atoms next to nontrivial
tailored surfaces is a rigorous test of quantum electrodynamics. Engineering
Casimir-Polder interactions represents a significant step towards atom trapping
in the extreme near field, possibly without the use of external fields.Comment: 21 pages, 9 figure
Coupling of atomic quadrupole transitions with resonant surface plasmons
We report on the coupling of an electric quadrupole transition in atom with
plasmonic excitation in a nanostructured metallic metamaterial. The quadrupole
transition at 685 nm in the gas of Cesium atoms is optically pumped, while the
induced ground state population depletion is probed with light tuned on the
strong electric dipole transition at 852 nm. We use selective reflection to
resolve the Doppler-free hyperfine structure of Cesium atoms. We observed a
strong modification of the reflection spectra at the presence of metamaterial
and discuss the role of the spatial variation of the surface plasmon polariton
on the quadrupole coupling.Comment: 6 pages, 5 figure
MAPPING OF FOCUSED LAGUERRE-GAUSS BEAMS: THE INTERPLAY BETWEEN SPIN AND ORBITAL ANGULAR MOMENTUM AND ITS DEPENDENCE ON DETECTOR CHARACTERISTICS
accepted for publication (april 18, 2012) in Physicial Review AInternational audienceWe show that propagating optical fields bearing an axial symmetry are not truly hollow in spite of a null electric field on-axis. The result, obtained by general arguments based upon the vectorial nature of electromagnetic fields, is of particular significance in the situation of an extreme focusing, when the paraxial approximation no longer holds. The rapid spatial variations of fields with a "complicated" spatial structure are extensively analyzed in the general case and for a Laguerre-Gauss beam 2 as well, notably for beams bearing a |l| = 2 orbital angular momentum for which a magnetic field and a gradient of the electric field are present on-axis. We thus analyze the behavior of a atomic size light-detector, sensitive as well to quadrupole electric transitions and to magnetic dipole transitions, and apply it to the case of Laguerre-Gauss beam. We detail how the mapping of such a beam depends on the nature and on the specific orientation of the detector. We show also that the interplay of mixing of polarization and topological charge, respectively associated to spin and orbital momentum when the paraxial approximation holds, modifies the apparent size of the beam in the focal plane. This even leads to a breaking of the cylindrical symmetry in the case of a linearly polarized transverse electric field
A Tabulation and Critical Analysis of the Wavelength-Dependent Dielectric Image Coefficient for the Interaction Exerted by a Surface onto a Neighbouring Excited Atom
The near-field interaction of an atom with a dielectric surface is inversely
proportional to the cube to the distance to the surface, and its coupling
strength depends on a dielectric image coefficient. This coefficient, simply
given in a pure electrostatic approach by (eps-1) / (eps+1) with eps the
permittivity, is specific to the frequency of each of the various relevant
atomic transition : it depends in a complex manner from the bulk material
properties, and can exhibit resonances connected to the surface polariton
modes. We list here the surface resonances for about a hundred of optical
windows whose bulk properties are currently tabulated. The study concentrates
on the infrared domain because it is the most relevant for atom-surface
interaction. Aside from this tabulation, we discuss simple hints to estimate
the position of surface resonances, and how uncertainties in the bulk data for
the material dramatically affect the predictions for the image coefficient. We
also evaluate the contribution of UV resonances of the material to the non
resonant part of the image coefficient.Comment: submitted (Jan. 23, 2006) to Optics Communication
Dicke Coherent Narrowing in Two-Photon and Raman Spectroscopy of Thin Vapour Cells
The principle of coherent Dicke narrowing in a thin vapour cell, in which
sub-Doppler spectral lineshapes are observed under a normal irradiation for a
l/2 thickness, is generalized to two-photon spectroscopy. Only the sum of the
two wave vectors must be normal to the cell, making the two-photon scheme
highly versatile. A comparison is provided between the Dicke narrowing with
copropagating fields, and the residual Doppler-broadening occurring with
counterpropagating geometries. The experimental feasibility is discussed on the
basis of a first observation of a two-photon resonance in a 300 nm-thick Cs
cell. Extension to the Raman situation is finally considered
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