Plasmonic quantum effects on single-emitter strong coupling

AbstractCoupling between electromagnetic cavity fields and fluorescent molecules or quantum emitters can be strongly enhanced by reducing the cavity mode volume. Plasmonic structures allow light confinement down to volumes that are only a few cubic nanometers. At such length scales, nonlocal and quantum tunneling effects are expected to influence the emitter interaction with the surface plasmon modes, which unavoidably requires going beyond classical models to accurately describe the electron response at the metal surface. In this context, the quantum hydrodynamic theory (QHT) has emerged as an efficient tool to probe nonlocal and quantum effects in metallic nanostructures. Here, we apply state-of-the-art QHT to investigate the quantum effects on strong coupling of a dipole emitter placed at nanometer distances from metallic particles. A comparison with conventional local response approximation (LRA) and Thomas-Fermi hydrodynamic theory results shows the importance of quantum effects on the plasmon-emitter coupling. The QHT predicts qualitative deviation from LRA in the weak coupling regime that leads to quantitative differences in the strong coupling regime. In nano-gap systems, the inclusion of quantum broadening leads to the existence of an optimal gap size for Rabi splitting that minimizes the requirements on the emitter oscillator strength

Nanowire-Intensified MEF in Hybrid Polymer-Plasmonic Electrospun Filaments

Hybrid polymer-plasmonic nanostructures might combine high enhancement of localized fields from metal nanoparticles with light confinement and long-range transport in subwavelength dielectric structures. Here we report on the complex behavior of fluorophores coupling to Au nanoparticles within polymer nanowires, which features localized metal-enhanced fluorescence (MEF) with unique characteristics compared to conventional structures. The intensification effect when the particle is placed in the organic filaments is remarkably higher with respect to thin films of comparable thickness, thus highlighting a specific, nanowire-related enhancement of MEF effects. A dependence on the confinement volume in the dielectric nanowire is also evidenced, with MEF significantly increasing upon reducing the wire diameter. These findings are rationalized by finite element simulations, predicting a position-dependent enhancement of the quantum yield of fluorophores embedded in the fibers. Calculation of the ensemble-averaged fluorescence enhancement unveils the possibility of strongly enhancing the overall emission intensity for structures with size twice the diameter of the embedded metal particles. These new, hybrid fluorescent systems with localized enhanced emission, as well as the general Nanowire-Intensified MEF effect associated to them, are highly relevant for developing nanoscale light-emitting devices with high efficiency and inter-coupled through nanofiber networks, highly sensitive optical sensors, and novel laser architectures.Comment: 29 pages, 12 figures, Small (2018

Instationaeres Motorgeraeusch I Die Geraeuschemission direkteinspritzender Dieselmotoren unter instationaeren Betriebsbedingungen - Ursachen und Massnahmen zur Verringerung. Abschlussbericht

With 129 figs., 8 tabs., 9 refs.Copy held by UB/TIB Hannover / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Plasmonic Nonlocal Response Effects on Dipole Decay Dynamics in the Weak- and Strong-Coupling Regimes

The largest increases in spontaneous decay rates of quantum emitters can be achieved using plasmonic structures that are characterized by closely spaced metallic elements. These systems can give rise to the smallest optical cavities attainable, offering a viable solution to achieve single molecule light-matter strong-coupling. On the other hand, their optical response might be strongly affected by nonlocal and quantum effects of the metal electron gas. In this work, we analyze the impact of nonlocal effects on the emission properties of a single quantum emitter coupled to a plasmonic system characterized by deeply subwavelength gap regions, in both the weak and the strong-coupling regimes. We find that the presence of nonlocality imposes strict limits to the achievability of strong-coupling with single molecules in apparent contrast to recent experiments, suggesting that a more refined theory might be required. These limits are even larger if a <i>k</i>-dependent absorption is included in the calculations. These results place boundaries to the applicability of hydrodynamic methods