487 research outputs found
Casimir-Polder effect with thermally excited surfaces
We take a closer look at the fundamental Casimir-Polder interaction between
quantum particles and dispersive dielectric surfaces with surface polariton or
plasmon resonances. Linear response theory shows that in the near field, van
der Waals, regime the free energy shift of a particle contains a thermal
component that depends exclusively on the population/excitation of the
evanescent surface polariton/plasmon modes. Our work makes evident the link
between particle surface interaction and near field thermal emission and
demonstrates how this can be used to engineer Casimir-Polder forces. We also
examine how the exotic effects of surface waves are washed out as the distance
from the surface increases. In the case of molecules or excited state atoms,
far field approximations result in a classical dipole-dipole interaction which
depends on the surface reflectivity and the mean number of photons at the
frequency of the atomic/molecular transition. Finally we present numerical
results for the CP interaction between Cs atoms and various dielectric surfaces
with a single polariton resonance and discuss the implications of temperature
and retardation effects for specific spectroscopic experiments.Comment: accepted in Phys. Rev.
Detection of Spiral photons in Quantum Optics
We show that a new type of photon detector, sensitive to the gradients of
electromagnetic fields, should be a useful tool to characterize the quantum
properties of spatially-dependent optical fields. As a simple detector of such
a kind, we propose using magnetic dipole or electric quadrupole transitions in
atoms or molecules and apply it to the detection of spiral photons in
Laguerre-Gauss (LG) beams. We show that LG beams are not true hollow beams, due
to the presence of magnetic fields and gradients of electric fields on beam
axis. This approach paves the way to an analysis at the quantum level of the
spatial structure and angular momentum properties of singular light beams.Comment: 5 pages, 4 figure
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
Anisotropic Atom-Surface Interactions in the Casimir-Polder Regime
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 0.03 Lambda, where Lambda is the atom characteristic wavelength.
Possible experimental verifications of this distance dependence are discussed.Comment: 5 pages, 2 figure
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
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
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
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