Generation of a light mode optimized for efficient free-space photon-atom coupling

Today the interaction of light and matter on the single quantum level is a wide research field. Strong coupling between a single photon and a single atom has already been achieved with optical cavities. Here, we treat strong interaction in free space, i.e. strong interaction whilst maintaining the free space density of states of the electromagnetic field. We pursue the coupling of a properly designed single photon wave packet to a single ion aiming at an excitation probability close to unity. For this purpose a linear dipole transition of an ion localized in the focal point of a deep parabolic mirror is addressed by a collimated laser beam focused onto the ion from nearly the full solid angle. In order to reach the highest possible coupling strength, the incident vectorial light field must be matched to the radiation pattern of the corresponding atomic transition both in the spatial and in the temporal domain. Here the generation of such an incident light mode is presented.