200 research outputs found
Circuit Model of Plasmon-Enhanced Fluorescence
No full textHybridized decaying oscillations in a nanosystem of two coupled elements—a quantum emitter and a plasmonic nanoantenna—are considered as a classical effect. The circuit model of the nanosystem extends beyond the assumption of inductive or elastic coupling and implies the near-field dipole-dipole interaction. Its results fit those of the previously developed classical model of Rabi splitting, however going much farther. Using this model, we show that the hybridized oscillations depending on the relationships between design parameters of the nanosystem correspond to several characteristic regimes of spontaneous emission. These regimes were previously revealed in the literature and explained involving semiclassical theory. Our original classical model is much simpler: it results in a closed-form solution for the emission spectra. It allows fast prediction of the regime for different distances and locations of the emitter with respect to the nanoantenna (of a given geometry) if the dipole moment of the emitter optical transition and its field coupling constant are known
Experimental verification of the suppression of spatial dispersion in artificial plasma
No full textIn this paper, we verify experimentally the recently proposed theory on suppression of the spatial dispersion in an artificial plasma. We make use of the image principle and assume effectively local material parameters of the artificial plasma, in which the spatial dispersion has been suppressed, and measure the reflection from an impenetrable grounded surface. The plasma resonance can be clearly distinguished from the measurement results at the plasma frequency independently from the incidence angle. The agreement between the measurement results and the theory and simulations is very good
Angular and Polarization Stability of Broadband Reconfigurable Intelligent Surfaces of Binary Type
No full textRecently, reconfigurable intelligent surfaces (RISs) gained notable consideration due to their ability to provide efficient and cost-effective wireless communication networks. However, this powerful concept often suffers from simplistic modeling which underestimates such features of RIS as the resonant frequency dispersion and strong angular dependency of the reflection phases for both TE and TM polarizations of the incident wave. The angular and polarization instability of the reflection phase is a fundamental restriction of RISs, especially restrictive if the operation frequency band is broad. In this paper, we address this challenge for a binary RIS performed as a metasurface. We have studied the reflection phase frequency dispersion (RPFD) analytically that allowed us to engineer the needed angular and polarization properties of the RIS. Our RIS is a self-resonant grid of Jerusalem crosses located on a thin metal-backed dielectric substrate. Adjacent crosses are connected by switchable capacitive loads. We have shown the advantage of our metasurface compared to switchable mushroom-field structures and meta-gratings of resonant patches. An RIS is also fabricated and measured, and the experimental results corroborate well our numerical full wave simulations and analytical predictions
Tunable Optimal Anomalous Reflection Using Discrete Impedance Metasurfaces
No full textPublisher Copyright: © 2024 18th European Conference on Antennas and Propagation, EuCAP 2024. All Rights Reserved. | openaire: EC/H2020/956256/EU//META WIRELESSThe cutting-edge RIS technology enables accurate management of electromagnetic waves within wireless environments. In this study, we aim to achieve the maximal efficiency of the targeted anomalous reflection without scattering at unwanted angles even if the needed reflection angle is very large. To address this, we present a robust optimization technique that utilizes a mode-matching approach for a periodically non-uniform metasurface. It uses the apparatus of discretized sheet impedance and ensures the easy implementation and passivity of the metasurface.Peer reviewe
Circuit theory of metal-enhanced fluorescence
No full textMetal-enhanced fluorescence (MEF) comprises several linear phenomena which can be successfully described either by a classical theory or by a quantum one. Usually different phenomena are described by different classical models. Recently, an analytical model for a metal nanoantenna coupled to a quantum emitter was suggested that grants an approximate solution covering all basic linear phenomena observed in MEF from the Purcell effect to the fluorescent quenching. In this paper, the further development of this model is presented in terms of the equivalent circuits. The circuit model allows us to express the non-radiative Purcell factor of a nanoantenna through the previously evaluated radiative Purcell factor, to find the threshold of the fluorescence quenching and to determine the conditions when a fluorescent nanostructure transforms into a surface-plasmon laser (spaser).Peer reviewe
On the design of reflecting intelligent surfaces for multi-user NOMA communication networks
No full textPublisher Copyright: © 2024 IEEE. | openaire: EC/H2020/956256/EU//META WIRELESSReconfigurable intelligent surfaces offer potential opportunity for wireless signal manipulation. In Power Domain Non-Orthogonal Multiple Access (P-D NOMA), ensuring users receive specific power from the base station is vital. Our paper introduces a semi-analytical method using unequal coefficients superposition to derive closed-form formulas for estimating the beam directivity in large RISs. Employing simplifications to achieve these formulas, we validate their accuracy via full-wave simulations.Peer reviewe
Advancing RIS Beamforming Efficiency: Moving Beyond Diagonal Matrix Techniques
No full text| openaire: EC/H2020/956256/EU//META WIRELESSOptimizing wireless propagation channels is essential for advancing future communication technologies, particularly in dynamic vehicular environments where high vehicle mobility is a challenge. This paper introduces a novel practical implementation of reconfigurable intelligent surfaces (RIS) that achieve highly efficient beamforming, significantly surpassing the limitations of the conventional diagonal phase shift approach. We expand the theoretical and optimization framework based on the discrete impedance model to accommodate practical design scenarios. We validate our approach by fabricating an RIS prototype and conducting experimental measurements using the parallel plate waveguide technique. The experimental results confirm the superior performance of our approach, demonstrating at least a 30% improvement in efficiency over diagonal matrix methods, thereby enhancing signal quality and coverage. This ensures seamless communication and ubiquitous connectivity, improving the quality of service by boosting the received signal.Peer reviewe
Broadband Operation of Binary Metasurfaces: Limitations and Perspectives
No full textPublisher Copyright: ©2013 IEEE. | openaire: EC/H2020/956256/EU//META WIRELESSIn this paper, physical prerequisites of the broadband operation of reflective intelligent surfaces (RIS) implemented as periodically non-uniform metasurfaces (MSs) of binary type are elucidated. The general relation for the maximal operational band of a binary MS following from these prerequisites is deduced. Based on this relation, the general rules for engineering the periodical RISs based on the binary MSs with the maximally broad frequency band are formulated. Recent studies in which this maximum was approached are discussed. Finally, we present a numerical example of an original binary MS designed with these guidelines which grants for restricted incidence angles an ultra-broadband operation.Peer reviewe
Accurate Estimation of non-Resonant Far-Field Superresolution by a Glass Microparticle
No full textPublisher Copyright: © 2023 IEEE.In this paper, we theoretically study the spatial resolution granted by a glass microsphere to two pointwise dipoles separated by a tiny gap and located on the sphere surface. This resolution is considered via parameters of the so-called virtual sources effectively shaped by the microparticle of the radiation of the real sources. The geometrical optics qualitatively explains these virtual sources, but only full-wave simulations give a reliable information of their location and sizes. We developed a method for finding these sources from COMSOL simulations. The virtual source is defined as the waist of the wave beam obtained from the imaging beam by its exact inversion performed at a very large distance from the microparticle. We have obtained both pessimistic and optimistic estimates for the ultimate resolution. We found that the novel scenario of the microparticle imaging theoretically revealed in our previous work, promises much finer resolution than the conventional scenario.Peer reviewe
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