- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Dark Plasmon Modes in Symmetric Gold Nanoparticle Dimers Illuminated by Focused Cylindrical Vector Beams
摘要： The plasmon hybridization model of electromagnetic coupling between plasmonic nanoparticles predicts the formation of lower energy “bonding” and higher energy “antibonding” modes in analogy with the quantum mechanical description of chemical bonding. For a symmetric metallic nanoparticle dimer excited by linearly polarized light, the hybridization picture predicts that in-phase coupling of the dipole moments is optically allowed, creating bright “modes”, whereas the out-of-phase coupling is dark due to the cancellation of the oppositely oriented dipole moments (in the quasistatic approximation). These bright modes are electric dipolar in nature and readily couple to scalar (i.e., linearly or circularly polarized) beams of light. We show that focused cylindrical vector beams, specifically azimuthally and radially polarized beams, directly excite dark plasmon modes in symmetric gold nanoparticle (AuNP) dimers at normal incidence. We use single-particle spectroscopy and electrodynamics simulations to study the resonance scattering of AuNP dimers illuminated by azimuthally and radially polarized light. The electric field distributions of the focused azimuthal or radial beams are locally polarized perpendicular or parallel to the AuNP dimer axis, but with opposite directions at each particle. Therefore, the associated combinations of single-particle dipole moments are out-of-phase, and the excitation (resonance) is of so-called “dark modes”. In addition, multipole expansion of the fields associated with each scattering spectrum shows that the vector beam excitation involves driving multipolar, e.g., magnetic dipolar and electric quadrupolar, modes, and that they even dominate the scattering spectra (vs electric dipole). This work opens new opportunities for investigating dark plasmon modes in nanostructures, which are difficult to selectively excite by conventional polarized light.
关键词： electrodynamics simulations,dark plasmon modes,plasmon hybridization,single-particle spectroscopy,gold nanoparticle dimers,cylindrical vector beams
更新于2025-09-23 15:21:21
-
Magnetic and Electric Solid-State Plasmon Spherical Resonators
摘要： Electrodynamic study of solid-state plasmon spherical resonators applicable in the range from microwave to optical frequencies is undertaken. Influence of dimensions and electromagnetic properties of media on the resonance frequency and Q-factor of these resonators is analyzed. It is shown that transcendental equations resulting from electrodynamic analysis of plasmon resonators can be also applied to the analysis of whispering gallery resonators if the resonator’s medium is isotropic, although this is a completely different kind of a resonator. Special attention is focused on the Q-factor analysis and theoretical and practical Q-factor limits for the magnetic plasmon and the electric plasmon resonators. In the addition, the impact of the finite size of a resonator on the resonance frequency and Q-factor is considered. Computations of the resonance frequency and Q-factor of magnetic plasmon resonators are supported by experiments performed at microwave frequencies.
关键词： Plasmon,Spherical resonators,Transcendental equations
更新于2025-09-23 15:21:21
-
Plasmon-Enhanced Photodegradation of Ionic Liquids with Ag Nanocubes/ZnO Microsphere Composites
摘要： Ionic liquids (ILs) have been a hot topic in the past decades because of their unique properties and promising applications in various areas. However, the toxicity of ILs and their possible risk to the environment and aquatic organisms have also been confirmed. Therefore, it is imperative to seek an efficient way to remove or degrade ILs in the polluted aqueous system. In this work, Ag nanocubes/ZnO microspheres composites have been designed, prepared, and used for the photocatalytic degradation of eight commonly used imidazolium-based ILs in aqueous solution. It is found that ZnO semiconductor photocatalyst with an Ag content of 1.12 at. % can degrade 90% of all these ILs within 7 h. The structural characterization, photoluminescence analysis, and discrete dipole approximation calculations showed that the loading of Ag nanocubes onto ZnO microspheres significantly improves the performance of ZnO for the IL degradation through hot electron transfer and electrical field enhancement. In addition, the formed intermediates in the degradation process of [C4 mim]Cl have been detected by gas chromatography?mass spectroscopy. A possible degradation mechanism is proposed and compared with those previously reported in the chemical degradation.
关键词： Photodegradation,Ionic liquids,Plasmon-enhanced,ZnO microspheres,Ag nanocubes
更新于2025-09-23 15:21:21
-
Selected mode mixing and interference visualized within a single optical nanoantenna
摘要： Interference-based directional antennas typically consist of multiple dipoles with properly set distances and phases, which cause constructive interferences towards certain directions in radiation or reception. For nano optical antennas, the directionality can be realized by superposition of multiple eigen modes in a single structure. Such mode mixing creates locally strong field enhancement, which should be properly controlled for energy-conversion or sensing applications. However, experimental verification of the nano optical field, or especially the hot-spots, created by interference of selected eigen modes is not trivial. We here visualize how optical fields are distributed when multiple modes interfere within a silver disk nano antenna. We use angle- and polarization-resolved cathodoluminescence based on scanning transmission electron microscopy to select specific modes and visualize the field distribution at the nanoscale. The interfered field distribution significantly changes depending on the detection angles even when the detection geometry is symmetric, which can be explained by the phase difference of the excited mode. The cathodoluminescence signals are also modeled as superpositions of analytical eigen mode functions consisting of multipoles in space and complex Lorentzians in frequency to reproduce the experimentally obtained photon maps.
关键词： Scanning Transmission Electron Microscopy,Surface Plasmon,Multipole,Cathodoluminescence,Nanodisk
更新于2025-09-23 15:21:21
-
Ag nanocrystals with nearly ideal optical quality: synthesis, growth mechanism, and characterizations
摘要： Though Ag nanocrystals are predicted as the best material for localized surface plasmon resonances (LSPR) in the visible light region, realization of their ideal LSPR properties is hindered by the stringent requirement, i.e., simultaneous control of their size, shape, crystallinity, and surface structure. To achieve this goal, a synthetic scheme in non-polar solvent coupled with mild oxidative-etching by H+ ions is established. With a trace amount of Cl- ions as catalysts, H+ ions (in the form of carboxylic acids) become active for selectively etching the nuclei (and small nanocrystals) with imperfect crystal structure, which results in a new growth mechanism for formation of monodisperse nanocrystals, namely “self-focusing of size/crystallinity distribution”. H+ ions, ligands, and other reagents in the scheme are confirmed to possess negligible effects on the surface dielectric properties of Ag nanocrystals. To eliminate radiative damping of LSPR, single-crystalline and monodisperse spherical Ag nanocrystals in the size range between 7 and 20 nm are synthesized using this one-pot scheme. With excellent control of all the structural parameters, the full-width-at-half-maximum of LSPR spectra of single-crystalline Ag nanocrystals match theoretical predictions in the entire size range, and the maximum quality factor (~20) of LSPR predicted by theory is realized. Raman enhancement factor of the single-crystalline Ag nanocrystals for crystal violet (excitation at 514 nm) is 5 times higher than that of the typical multi-twinned ones with the same size.
关键词： localized surface plasmon resonances,oxidative-etching,monodisperse,single-crystalline,Ag nanocrystals,Raman enhancement
更新于2025-09-23 15:21:21
-
Nonperturbative nonlinear effects in the dispersion relations for TE and TM plasmons on two-dimensional materials
摘要： We analytically obtain the dispersion relations for transverse-electric (TE) and transverse-magnetic (TM) surface plasmon-polaritons in a nonlinear two-dimensional (2D) conducting material with inversion symmetry lying between two Kerr-type dielectric media. To this end, we use Maxwell’s equations within the quasielectrostatic, weakly dissipative regime. We show that the wavelength and propagation distance of surface plasmons decrease due to the nonlinearity of the surrounding dielectric. In contrast, the effect of the nonlinearity of the 2D material depends on the signs of the real and imaginary parts of the third-order conductivity. Notably, the dispersion relations obtained by naively replacing the permittivity of the dielectric medium by its nonlinear counterpart in the respective dispersion relations of the linear regime are not accurate. We apply our analysis to the case of doped graphene and make predictions for the surface plasmon wavelength and propagation distance.
关键词： Maxwell’s equations,quasielectrostatic regime,weakly dissipative regime,nonlinear two-dimensional materials,surface plasmon-polaritons,doped graphene,Kerr-type dielectric media
更新于2025-09-23 15:21:21
-
Collective strong light-matter coupling in hierarchical microcavity-plasmon-exciton systems
摘要： Polaritons are compositional light-matter quasiparticles that arise as a result of strong coupling between the vacuum field of a resonant optical cavity and electronic excitations in quantum emitters. Reaching such a regime is often hard, as it requires materials possessing high oscillator strengths to interact with the relevant optical mode. Two-dimensional transition metal dichalcogenides (TMDCs) have recently emerged as promising candidates for realization of strong coupling regime at room temperature. However, these materials typically provide coupling strengths in the range of 10-40 meV, which may be insufficient for reaching strong coupling with low quality factor resonators. Here, we demonstrate a universal scheme that allows a straightforward realization of strong coupling with 2D materials and beyond. By intermixing plasmonic excitations in nanoparticle arrays with excitons in a WS2 monolayer inside a resonant metallic microcavity, we fabricate a hierarchical system with the collective microcavity-plasmon-exciton Rabi splitting exceeding ~500 meV at room temperature. Photoluminescence measurements of the coupled systems show dominant emission from the lower polariton branch, indicating the participation of excitons in the coupling process. Strong coupling has been recently suggested to affect numerous optical- and material-related properties including chemical reactivity, exciton transport and optical nonlinearities. With the universal scheme presented here, strong coupling across a wide spectral range is within easy reach and therefore exploring these exciting phenomena can be further pursued in a much broader class of materials.
关键词： TMDC,Strong plasmon-exciton coupling,collective Rabi splitting,monolayer WS2
更新于2025-09-23 15:21:21
-
Recent progress in all-fiber non-Gaussian optical beam shaping technologies
摘要： Rapid development of fiber lasers are being followed by wide ranges of applications in laser processing technologies. One of the key parameters to determine the laser-matter interaction is beam shape and there have been intense research activities on beam shaping using bulk-optics. However, fiber optic solutions would take clear advantages over bulk-optics especially for fiber laser sources in terms of the beam conversion efficiency, the throughput power, and the compact footprint. In this article, all-fiber optical beam shaping technologies are reviewed and they are categorized as the phase front modification on the fiber facet, the surface plasmonics on fiber, all-fiber Fourier transformation, and multimode interference. Their physical principles, beam shaping capability, and some of the novel applications are explained
关键词： Phase front engineering,Laser beam,Surface plasmon polariton,Beam Shaping,Multimode Interference,Fourier Transform,Fiber Optics,Single mode optical fiber
更新于2025-09-23 15:21:21
-
Exploring the transfer squeezing properties from photons to the symmetric and asymmetric SPP modes
摘要： Quantum surface plasmon polariton (SPP) is a growing research area with many unknown phenomena. In this paper, the behavior of the squeezed SPP modes on the metal slab is assessed. To begin with, a quantized form of the SPP modes propagating on the metal thin film based on the Green’s tensor method is provided. Since the squeezing properties of the SPP modes are indeed transferred from incident photons, at the next step, different aspects of this phenomenon are studied. Obtaining an important direct relation between incident photons’ properties and SPP modes, will allow for the effective factors on this phenomenon to be explored. Although the initial quantum properties will be changed or lost during the photons- surface plasmon interaction, it will be shown that some factors can improve the transfer process. Finally, the squeezing transfer from incident photons to the SPP modes and effective factors on it as a full quantum phenomenon will be investigated.
关键词： squeezed SPP modes,quantum properties transfer,Quantum surface plasmon polariton,Green’s tensor method
更新于2025-09-23 15:21:21
-
[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - On the Contribution of Thermally Generated Surface Plasmon-Polaritons to Heat Radiation of Metal Objects
摘要： We present theoretical and experimental evaluations of the thermally generated surface plasmon polaritons (TSPPs) contribution to heat radiation of metal objects. It is found that this contribution is significant only for the edges of such objects flat facets observed at sliding angles to the facets planes and it is p-polarized. The analytical model for calculation the spectrum and the integral intensity of the entire set of TSPPs arriving to the edge of their sources line has been developed. In contrast to thermal radiation, intensity of TSPPs is proportional to the third rather than fourth degree of temperature, while the TSPP spectrum is shifted towards low frequencies relative to the thermal radiation spectrum.
关键词： thermally generated surface plasmon polaritons,metal objects,heat radiation,p-polarized,analytical model
更新于2025-09-23 15:21:21