Atomic optical antennas

Nanoscale antennas are an important tool within optics due to their ability to guide and concentrate light, and thus find application in fields ranging from communications to sensing and imaging. While such antennas are normally fabricated, nanoscale structures, a single point-like atom constitutes an intriguing alternative. Ideally, as a point-like dipole, and upon excitation with light that is resonant with an electronic transition, it will generate an electromagnetic field whose strength will diverge with decreasing distance to the atom. However, despite the appeal of this nominally "infinite" field enhancement, most real atomic dipoles in solids suffer from environmental induced decoherence that largely mitigates this effect. In this work, we collaborate with the experimental group of Alex High (Univ. Chicago) to demonstrate that certain atomic dipoles in diamond -- so-called germanium vacancy color centers -- are exemplary antennas due to their exceptional coherence. We show that individual color centers can exhibit up to a million-fold field intensity enhancement when driven by resonant light. We further utilize this atomic antenna as a probe to study, elucidate, and control the charge state dynamics of other nearby color centers, the physics of which has remained elusive until now. We anticipate that these atomic antennas in solid state should open interesting new applicatoins in spectroscopy, sensing, and quantum science.