Atomic Response in the Near-Field of Nanostructured Plasmonic Metamaterial.

We report on reflection spectra of cesium atoms in close vicinity of a nanostructured metallic meta-surface. We show that the hyperfine sub-Doppler spectrum of the 6(2)S1/2-6(2)P3/2 resonance transition at 852 nm is strongly affected by the coupling to the plasmonic resonance of the nanostructure. Fine tuning of dispersion and positions of the atomic lines in the near-field of plasmonic metamaterials could have uses and implications for atom-based metrology, sensing, and the development of atom-on-a-chip devices.

Doppler-free approach to optical pumping dynamics in the 6S1/2-5D5/2 electric quadrupole transition of cesium vapor.

The 6S1/2-5D5/2 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 the 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.

Detecting photons in the dark region of Laguerre-Gauss beams.

We show that a photon detector, sensitive to the magnetic field or to the gradient of electric field, can help to characterize the quantum properties of spatially-dependent optical fields. We discuss the excitation of an atom through magnetic dipole or electric quadrupole transitions with the photons of a Bessel beam or a Laguerre-Gauss (LG) beams. These spiral beams are shown to be 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 propagating light beams having a complicated spatial structure.

Temperature dependence of the dielectric permittivity of CaF(2), BaF(2) and Al(2)O(3): application to the prediction of a temperature-dependent van der Waals surface interaction exerted onto a neighbouring Cs(8P(3/2)) atom.

The temperature behaviour in the range 22-500 °C of the dielectric permittivity in the infrared range is investigated for CaF(2), BaF(2) and Al(2)O(3) through reflectivity measurements. The dielectric permittivity is retrieved by fitting reflectivity spectra with a model taking into account multiphonon contributions. The results extrapolated from the measurements are applied to predict a temperature-dependent atom-surface van der Waals interaction. We specifically consider as the atom of interest Cs(8P(3/2)), the most relevant virtual couplings of which fall in the range of thermal radiation and are located in the vicinity of the reststrahlen band of fluoride materials.

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. We perform a spectroscopic selective reflection measurement of the Casimir-Polder interaction between a Cs(6P3/2) 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 nonresonant 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 toward atom trapping in the extreme near field, possibly without the use of external fields.

Casimir-Polder interactions in the presence of thermally excited surface modes.

The temperature dependence of the Casimir-Polder interaction addresses fundamental issues for understanding vacuum and thermal fluctuations. It is highly sensitive to surface waves, which, in the near field, govern the thermal emission of a hot surface. Here we use optical reflection spectroscopy to monitor the atom-surface interaction potential between a Cs*(7D3/2) atom and a hot sapphire surface at distances of ~100 nm. In our experiments, that explore a large range of temperatures (500-1,000 K), the surface is at thermal equilibrium with the vacuum. The observed increase of the interaction with temperature, by up to 50%, relies on the coupling between atomic virtual transitions in the infrared range and thermally excited surface-polariton modes. We extrapolate our findings to a broad distance range, from the isolated atom to the short distances relevant to physical chemistry. Our work also opens the prospect of controlling atom-surface interactions by engineering thermal fields.

Resonant quenching of gas-phase Cs atoms induced by surface polaritons.

Near-field coupling between an excited atom and a surface-polariton mode can dramatically modify atomic branching ratios, because of surface-induced enhancement of a resonant decay channel. We show here that Cs(6D(3/2)) transfer towards Cs(7P(1/2)) (at lambda = 12.15 microm), negligible in free space, becomes efficient in the vicinity (< or =100 nm) of a sapphire window, due to a 12 microm resonance in the surface-polariton modes. The experiment relies on a selective reflection probing on the 7P(1/2)-10D(3/2) transition.