Direct Measurement of the Van Der Waals Interaction Between an Atom and Its Images in a Micron-Sized Cavity

The authors have measured by laser spectroscopy the energy of interaction between a sodium atom and its images in the walls of a micron-sized cavity. This cavity-QED study is the first direct quantitative test of the Lennard-Jones van der Waals interaction as a function of controlled atom-surface separation and mean-square electric dipole moment

Measurement of the Casimir-Polder Force

The authors have studied the deflection of ground-state sodium atoms passing through a micron-sized parallel-plate cavity by measuring the intensity of a sodium atomic beam transmitted through the cavity as a function of cavity plate separation. This experiment provides clear evidence for the existence of the Casimir-Polder force, which is due to modification of the ground-state Lamb shift in the confined space of a cavity. The results confirm the magnitude of the force and the distance dependence predicted by quantum electrodynamics

Using atomic interference to probe atom-surface interaction

We show that atomic interference in the reflection from two suitably polarized evanescent waves is sensitive to retardation effects in the atom-surface interaction for specific experimental parameters. We study the limit of short and long atomic de Broglie wavelength. The former case is analyzed in the semiclassical approximation (Landau-Zener model). The latter represents a quantum regime and is analyzed by solving numerically the associated coupled Schroedinger equations. We consider a specific experimental scheme and show the results for rubidium (short wavelength) and the much lighter meta-stable helium atom (long wavelength). The merits of each case are then discussed.Comment: 11 pages, including 6 figures, submitted to Phys. Rev. A, RevTeX sourc

Towards surface quantum optics with Bose-Einstein condensates in evanescent waves

We present a surface trap which allows for studying the coherent interaction of ultracold atoms with evanescent waves. The trap combines a magnetic Joffe trap with a repulsive evanescent dipole potential. The position of the magnetic trap can be controlled with high precision which makes it possible to move ultracold atoms to the surface of a glass prism in a controlled way. The optical potential of the evanescent wave compensates for the strong attractive van der Waals forces and generates a potential barrier at only a few hundred nanometers from the surface. The trap is tested with Rb Bose-Einstein condensates (BEC), which are stably positioned at distances from the surfaces below one micrometer

Efficient coupling of photons to a single molecule and the observation of its resonance fluorescence

Single dye molecules at cryogenic temperatures display many spectroscopic phenomena known from free atoms and are thus promising candidates for fundamental quantum optical studies. However, the existing techniques for the detection of single molecules have either sacrificed the information on the coherence of the excited state or have been inefficient. Here we show that these problems can be addressed by focusing the excitation light near to the absorption cross section of a molecule. Our detection scheme allows us to explore resonance fluorescence over 9 orders of magnitude of excitation intensity and to separate its coherent and incoherent parts. In the strong excitation regime, we demonstrate the first observation of the Mollow triplet from a single solid-state emitter. Under weak excitation we report the detection of a single molecule with an incident power as faint as 150 attoWatt, paving the way for studying nonlinear effects with only a few photons.Comment: 6 figure

Single molecules, single nanoparticles and their optical interaction

We have applied a new method to localize single dye molecules with nanometer resolution in three dimensions by means of the Stark effect. With this method we were able to resolve two molecules which were so close to each other that they underwent a strong dipole-dipole interaction. A quantitative spectral study of this system allowed us to determine the coupling parameters. In the second part of this paper we discuss our research on metal nanoparticles. We have developed a method to mount single nanoparticles at the very end of a fibre tip. We have used such probes as well defined scattering centers for apertureless scanning near-field optical microscopy. In this article we also discuss our efforts to examine the interaction of a single metal nanoparticle and a single molecule in a controlled manner

Nanometer resolution and coherent optical dipole coupling of two individual molecules

By performing cryogenic laser spectroscopy under scanning probe electrode that induces local electric field, we have resolved two individual fluorescent molecules separated by 12 nanometers in an organic crystal. The two molecules undergo strong coherent dipole-dipole coupling that produces entangled sub- and superradiant states. Under intense laser illumination, both molecules are excited via two-photon transition, and the fluorescence from this doubly excited system displays photon bunching. Our experimental scheme can be used to optically resolve molecules at the nanometer scale and to manipulate the degree of entanglement among them

Aligned terrylene molecules in a spin-coated ultrathin crystalline film of p-terphenyl

We report on the use of a simple spin casting procedure to fabricate very thin crystalline films of P-terphenyl doped with fluorescent terrylene molecules. By performing single molecule studies, we show that the guest molecules are oriented normal to the plane of the film. We find that despite the very low thickness of the p-terphenyl matrix. as thin as only 20 molecular layers, about half of the embedded emitters withstand photobleaching for illumination times of at least a day. (C) 2004 Elsevier B.V. All rights reserved