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 .
Single emitters integrated in plasmonic-dielectric waveguide structuresTremendous enhancement of light-matter interaction in plasmonic-dielectric hybrid devices allows for non-linearities at the level of single emitters and few photons, such as single photon transistors. However, constructing integrated components for such devices is technologically extremely challenging. We tackle this task by lithographically fabricating an on-chip plasmonic waveguide-structure connected to far-field in- and out-coupling ports via low-loss dielectric waveguides .
Single molecules in quantum radiometrySingle-photon sources (SPSs) based on quantum emitters hold promise in quantum radiometry as metrology standard for photon fluxes at the low light level. Ideally this requires control over the photon flux in a wide dynamic range, sub-Poissonian photon statistics, and narrow-band emission spectrum. In this work, a monochromatic SPS based on an organic dye molecule is presented, whose photon flux is traceably measured to be adjustable between 144 000 and 1320 000 photons per second at a wavelength of (785.6 ± 0.1) nm, corresponding to an optical radiant flux between 36.5 and 334 fW. The high purity of the single-photon stream is verified, with a second-order autocorrelation function at zero time delay below 0.1 throughout the whole range. Such molecule-based SPS is hence used for the calibration of a single-photon avalanche detector against a low-noise analog photodiode traceable to the primary standard for optical radiant flux (i.e., the cryogenic radiometer). Due to the narrow bandwidth of the source, corrections to the detector efficiency arising from the spectral power distribution are negligible. With this major advantage, the developed device may finally realize a low-photon-flux standard source for quantum radiometry. 
-  Simona Checcucci, Pietro Lombardi, Sahrish Rizvi, Fabrizio Sgrignuoli, Nico Gruhler, Frederik B. C. Dieleman, Francesco S. Cataliotti, Wolfram H. P. Pernice, Mario Agio and Costanza Toninelli. Beaming light from a quantum emitter with a planar optical antenna, Light: Science and Applications (2017).
-  Günter Kewes, Max Schoengen, Oliver Neitzke, Pietro Lombardi, Rolf-Simon Schönfeld, Giacomo Mazzamuto, Andreas W. Schell, Jürgen Probst, Janik Wolters, Bernd Löchel, Costanza Toninelli and Oliver Benson. A realistic fabrication and design concept for quantum gates based on single emitters integrated in plasmonic-dielectric waveguide structures, Scientific Reports 6, Article number: 28877 (2016).
-  P. Lombardi, M. Trapuzzano, M. Colautti, G. Margheri, I. P. Degiovanni, M. López, S. Kück, and C. Toninelli. A Molecule-Based Single-Photon Source Applied in Quantum Radiometry, Advanced Quantum Technologies (2019).