Beaming light from a quantum emitter with a planar optical antenna

The efficient interaction of light with quantum emitters is crucial to most applications in nano and quantum photonics, such as sensing or quantum information processing. Effective excitation and photon extraction are particularly important for the weak signals emitted by a single atom or molecule. Recent works have introduced novel collection strategies, which demonstrate that large efficiencies can be achieved by either planar dielectric antennas combined with high numerical aperture objectives or optical nanostructures that beam emission into a narrow angular distribution. However, the first approach requires the use of elaborate collection optics, while the latter is based on accurate positioning of the quantum emitter near complex nanoscale architectures; hence, sophisticated fabrication and experimental capabilities are needed. Here we present a theoretical and experimental demonstration of a planar optical antenna that beams light emitted by a single molecule, which results in increased collection efficiency at small angles without stringent requirements on the emitter position. The proposed device exhibits broadband performance and is spectrally scalable, and it is simple to fabricate and therefore applies to a wide range of quantum emitters. Our design finds immediate application in spectroscopy, quantum optics and sensing. Optical nanoantennas: simple strategy for focusing quantum-emitter light A flat optical nanoantenna capable of beaming light emitted by a single molecule has been studied theoretically and experimentally. Current strategies for boosting the collection efficiency of quantum emitters such as single atoms and molecules are inflexible and fiddly to implement. Now, Mario Agio of the University of Siegen, Germany, and CNR-INO, Italy, and Costanza Toninelli of the European Laboratory for Nonlinear Spectroscopy and CNR-INO, Italy, and co-workers in Italy, Germany and the UK have theoretically proposed and experimentally demonstrated a planar optical nanoantenna that funnels light emitted from a single molecule into a narrow beam, thus boosting the light collection efficiency. Unlike previous approaches, their strategy does not depend stringently on the position of the emitter. Furthermore, it is straightforward to fabricate, broadband and scalable across the spectrum. The team anticipates it will be rapidly adopted in spectroscopy, quantum optics and sensing applications.