Atomic optical antennas in solids

A resonantly excited atomic optical dipole simultaneously generates propagating (far) and evanescent (near) electromagnetic fields. The near-field component diverges in the limit of decreasing distance, indicating an optical antenna with the potential for enormous near-field intensity enhancement. In principle, any atomic optical dipole in a solid can serve as an optical antenna; however, most of them suffer from environmentally induced decoherence that largely mitigates field enhancement. Here we demonstrate that germanium vacancy centres in diamond—optically coherent atom-like dipoles in a solid—are exemplary antennas. We measure up to million-fold optical intensity enhancement in the near-field of resonantly excited germanium vacancies. In addition to the rich applications already developed for conventional nanoantennas, atomic antennas in the solid state promise to yield interesting new applications in spectroscopy, sensing and quantum science. As one concrete example, we use germanium vacancy antennas to detect and control the charge state of nearby carbon vacancies and generate measurable fluorescence from individual vacancies through Förster resonance energy transfer.