Optical antennas in hybrid photonic systems

Plasmonic nano-antennas are widely employed for sensing and enhancing light-matter interactions. They are characterized by deeply subwavelength optical mode volumes as well as broad resonance linewidths. By coupling nano-antennas to resonant modes of dielectric photonic cavities, which have a larger mode volumes in combination with very high-Q resonances, a hybrid system is created with eigenmodes that combine the traits of the individual constituents in a highly versatile fashion. The resulting systems are suitable to achieve strong field enhancements over a tunable bandwidth. We study the properties of the resulting eigenmodes of the coupled system, and show how they can be used for both efficient excitation as well as extraction of radiation. We experimentally realize a system consisting of nano-antennas coupled to a silica whispering gallery mode resonator. We show how this can be used to quantify the change of the antenna polarizability related to the alteration of the local density of states by the nearby microcavity mode. Moreover, we study the eigenmodes of the hybrid system in terms of their spectral and radiation properties. We observe pronounced alterations of the cavity frequency and linewidth when it is perturbed by nano-antennas, and systematically investigate the dependence of those shifts on the properties of the nano-antennas.