ATOMS IN MICRON-SIZED METALLIC AND DIELECTRIC WAVE-GUIDES

Over the past ten years, our group has investigated the effects of con finement on atoms inside metallic micron-sized cavities in order to el ucidate some basic phenomena in the field of cavity quantum electrodyn amics (QED). The first of these was the inhibition of spontaneous emis sion from an atom inside a cavity. This was followed by a laser spectr oscopic measurement of the van der Waals interaction between a single Rydberg atom and a gold cavity, which showed that a simple electrostat ic model of the atom-cavity interaction is correct when the cavity is small enough. More recently, the retarded Casimir-Polder force was mea sured between a ground state sodium atom and a large cavity, demonstra ting that the van der Waals potential fails at long enough range and t hat the vacuum fluctuations of the field then have an important role i n the interaction of the atom with the cavity. Our group is now pushin g forward these investigations to study cavities whose walls have loss es and dispersion, where the theory of cavity QED is significantly mor e complicated. With real surfaces, we have to deal with the complex di electric response epsilon(omega) of the material, which exhibits frequ ency-dependent absorption and dispersion. One particularly interesting case is when a downward transition in the atom is resonant with an ex citation of the cavity walls. This opens a new branch for the atomic d ecay: as an alternative to creating a photon within the space surround ed by the cavity walls the atomic decay can now create an electromagne tic excitation of the walls themselves. Another novel feature of our e xperiments is that the Bohr frequencies of the atom are close to the k (T)/h, where T is room temperature. We therefore expect to be able to measure effects associated with QED at finite temperature; in other wo rds, to study how the blackbody radiation affects our experiments. By conducting experiments with real surfaces, we hope to elucidate and pe rhaps simplify the theoretical models used to describe these systems.