Strong coupling between single atoms and non-transversal photons

Full text: We investigate the interaction between single quantum emitters and non-transversally polarized photons for which the electric field vector amplitude has a significant component in the direction of propagation. Even though this situation seems to be at odds with the description of light as a transverse wave, it regularly occurs when inter-facing or manipulating emitters with non-paraxial, guided, or evanescent light. Here, we quantitatively investigate this phenomenon for the case of single 85Rb atoms that strongly interact with a bottle-micro resonator - a novel type of whispering-gallery-mode (WGM) micro resonator. Our experimental results show that the non-transversal polarization decisively alters the physics of light–matter interaction. In addition they demonstrate that WGM resonators constitute a novel class of micro resonators that can, e.g., simultaneously sustain three orthogonally polarized eigenmodes. Building on our improved understanding, we investigate pathways to future WGM resonator based photonic devices. As a first example, we simultaneously interface the resonator with two coupling fibers, and use a single atom to route the incoming light between the optical fibers. (author)