Mario Agio

Highly Efficient Interfacing of Guided Plasmons and Photons in Nanowires

Successful exploitations of strongly confined surface plasmon-polaritons critically rely on their efficient and rapid conversion to lossless channels. We demonstrate a simple, robust, and broadband butt-coupling technique for connecting a metallic nanowire and a dielectric nanofiber. Conversion efficiencies above 95% in the visible and close to 100% in the near-infrared can be achieved with realistic parameters. Moreover, by combining butt-coupling with nanofocusing, we propose a broadband high-throughput near-field optical microscope.

Metallodielectric hybrid antennas for ultrastrong enhancement of spontaneous emission.

We devise new optical antennas that reduce the excited-state radiative lifetimes of emitters to the order of 100xa0fs while maintaining quantum efficiencies of about 80% at a broadband operation. Here, we combine metallic nanoparticles with planar dielectric structures and exploit design strategies from plasmonic nanoantennas and concepts from cavity quantum electrodynamics to maximize the local density of states and minimize the nonradiative losses incurred by the metallic constituents. The proposed metallodielectric hybrid antennas promise an important impact on various fundamental and applied research fields, including photophysics, ultrafast plasmonics, bright single-photon sources, and Raman spectroscopy.

Fluorescence Enhancement with the Optical (Bi-) Conical Antenna†

We investigate the properties of finite gold nanocones as optical antennas for enhancing molecular fluorescence. We compute the modification of the excitation rate, spontaneous emission rate, and quantum efficiency as a function of the nanocone base and length, showing that the maximum field and fluorescence enhancements do not occur for the same nanocone parameters. We compare the results with those for nanorods and nanospheroids and find that nanocones perform better.

Coherent interaction of light with a metallic structure coupled to a single quantum emitter: from superabsorption to cloaking.

We provide a general theoretical platform based on quantized radiation in absorptive and inhomogeneous media for investigating the coherent interaction of light with material structures in the immediate vicinity of quantum emitters. In the case of a very small metallic cluster, we demonstrate extreme regimes where a single emitter can either counteract or enhance particle absorption by 3 orders of magnitude. For larger structures, we show that an emitter can eliminate both scattering and absorption and cloak a plasmonic antenna. We provide physical interpretations of our results and discuss their applications in active metamaterials and quantum plasmonics.

Gold, Copper, Silver and Aluminum Nanoantennas to Enhance Spontaneous Emission

We compute the decay rates of emitters coupled to spheroidal nanoantennas made of gold, copper, silver, and aluminum. The spectral position of the localized surface plasmon-polariton resonance, the enhancement factors and the quantum efficiency are investigated as a function of the aspect ratio, background index and the metal composing the nanoantenna. While copper yields results similar to gold, silver and aluminum exhibit different performances. Our results show that with a careful choice of the parameters these nanoantennas can enhance emitters ranging from the UV to the near-IR spectrum.

Large Suppression of Quantum Fluctuations of Light from a Single Emitter by an Optical Nanostructure

We investigate the reduction of the electromagnetic field fluctuations in resonance fluorescence from a single emitter coupled to an optical nanostructure. We find that such hybrid systems can lead to the creation of squeezed states of light, with quantum fluctuations significantly below the shot-noise level. Moreover, the physical conditions for achieving squeezing are strongly relaxed with respect to an emitter in free space. A high degree of control over squeezed light is feasible both in the far and near fields, opening the pathway to its manipulation and applications on the nanoscale with state-of-the-art setups.

Ultrabright single-photon source on diamond with electrical pumping at room and high temperatures

The recently demonstrated electroluminescence of color centers in diamond makes them one of the best candidates for room temperature single-photon sources. However, the reported emission rates are far off what can be achieved by state-of-the-art electrically driven epitaxial quantum dots. Since the electroluminescence mechanism has not yet been elucidated, it is not clear to what extent the emission rate can be increased. Here we develop a theoretical framework to study single-photon emission from color centers in diamond under electrical pumping. The proposed model comprises electron and hole trapping and releasing, transitions between the ground and excited states of the color center as well as structural transformations of the center due to carrier trapping. It provides the possibility to predict both the photon emission rate and the wavelength of emitted photons. Self-consistent numerical simulations of the single-photon emitting diode based on the proposed model show that the photon emission rate can be as high as 100 kcounts s

Robust luminescence of the silicon-vacancy center in diamond at high temperatures

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Beaming light from a quantum emitter with a planar optical antenna

at standard conditions. In contrast to most optoelectronic devices, the emission rate steadily increases with the device temperature achieving of more than 100 Mcount s

Dynamics of Single-Photon Emission from Electrically Pumped Color Centers

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