Experiments with toroidal microresonators in cavity QED

Abstract

Advances made pertaining to strong interactions between single photons of light and single atoms have great potential in the field of quantum information. However, scalability is a limiting factor in the applicability of current technologies (such as an atom in the mode of a Fabry-Perot resonator) due to difficulties in alignment and fabrication. Toroial resonators, however, are fabricated lithographically on silicon wafers, and are therefore easily scalable. Light is coupled into a toroid by tapered optical fiber, allowing for the efficient retrieval of photons from the resonator mode that is necessary if multiple resonators are to be eventually coupled to one another. We have demonstrated interactions between single atoms of cesium and a toroidal resonator that lie in the regime of strong coupling since the rate of coupling between an atom and the cavity mode, g0 m = (50±12) MHz, is much larger than the dissipative rates of the system (gamma, kappa)/2pi ~ (2.6, 18) MHz. To further expand upon the usefulness of toroids in cavity QED, I have striven to improve the way that toroids are characterized and coupled. An apparatus which semi-automates the characterization process reduces the length of time a toroid is outside of vacuum, thus limiting environmental degradation. To help in better understanding the process of pulling tapered fibers, the efficiency and characteristic quantities have been detailed. Similarly, the behavior of a toroid resonance as a function of coupling strength was quantified. Preliminary locking of the coupling by controlling the separation between the taper and toroid has been accomplished. This locking will allow the next generation of atom-toroid coupling to require less human intervention and therefore be more efficient.