278 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
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
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
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
Overcoming black body radiation limit in free space: Metamaterial superemitter
No full textHere, we demonstrate that the power spectral density of thermal radiation at a specific wavelength produced by a body of finite dimensions set up in free space under a fixed temperature could be made theoretically arbitrary high, if one could realize double negative metamaterials with arbitrary small loss and arbitrary high absolute values of permittivity and permeability (at a given frequency). This result refutes the widespread belief that Planck's law itself sets a hard upper limit on the spectral density of power emitted by a finite macroscopic body whose size is much greater than the wavelength. Here we propose a physical realization of a metamaterial emitter whose spectral emissivity can be greater than that of the ideal black body under the same conditions. Due to the reciprocity between the heat emission and absorption processes such cooled down superemitter also acts as an optimal sink for the thermal radiation - the 'thermal black hole' - which outperforms Kirchhoff-Planck's black body which can absorb only the rays directly incident on its surface. The results may open a possibility to realize narrowband super-Planckian thermal radiators and absorbers for future thermo-photovoltaic systems and other devices.Peer reviewe
Spatial Fano Resonance and its Implication for a Glass Microsphere
No full textPublisher Copyright: © 2023 IEEE.Fano's resonance is not obviously that of a system parameter depending on the state energy or frequency. The spatial distribution of light intensity may experience this resonance if the continuum of eigenmodes interferes with a resonant mode. We found this spatial Fano resonance in the exact solution of a diffraction problem: a hollow Bessel impinges on a dielectric sphere with optically substantial but not very large radius. Tuning the frequency, one may engineer a very sharp Fano minimum in free space. This point at which the electromagnetic field vanishes may serve an optical trap for molecules and atoms. In accordance with our calculations, such the trap has no analogues in the available literature in what concerns its parameters and its ultimate simplicity.Peer reviewe
Thin perfect absorbers for electromagnetic waves: Theory, design, and realizations
No full textPeer reviewe
Revisiting substrate-induced bianisotropy in metasurfaces
No full textRecently, it has been shown that a metasurface of plasmonic nanospheres deposited on a highly refractive substrate requires a bianisotropic magnetoelectric coupling for its effective description. The effect has been coined substrate-induced bianisotropy. It leads to an asymmetric reflectance similar to bianisotropic metasurfaces. In this work, through a circuit model, we show that such bianisotropy does not necessarily emerge for all substrated metasurfaces. Indeed, we show that the thickness of the metasurface plays a crucial role to encounter substrate-induced bianisotropy. Moreover, by taking advantage of substrate-induced bianisotropy, we present the necessary conditions for the circuit model parameters to compensate the asymmetric reflectance generated by an intrinsically bianisotropic metasurface. We finally express that, in substrated metasurfaces, the asymmetric reflectance and the bianisotropic response are two separate issues albeit with interdependencies.Peer reviewe
- …
