- 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
-
Plasmonics || Plasmonic Modes in Au and AuAg Nanowires and Nanowire Dimers Studied by Electron Energy Loss Spectroscopy
摘要： In this chapter, we review our recent work on the investigation of surface plasmon modes in metallic nanowires and nanowire dimers by means of electron energy loss spectroscopy combined with scanning transmission electron microscopy (STEM-EELS). Due to the very high spatial resolution, STEM-EELS is a powerful technique to visualize multipole order surface plasmon modes in nanowires and study the dependency of their resonance energies on different parameters such as nanowire dimensions or nanowire porosity. In addition, we investigate surface plasmon hybridization in nanowires separated by gaps of less than 10 nm or connected by small metallic bridges. In such structures new modes arise, which depend strongly on gap or bridge sizes. Experimental results are supported by finite element simulations. The investigated nanowires and dimers are fabricated by electrodeposition in etched ion-track templates, combined with a selective dissolution processes. The synthesis techniques and their advantages for the fabrication of plasmonic nanostructures are also discussed.
关键词： nanowire dimers,scanning transmission electron microscopy,ion-track technology,electron energy loss spectroscopy,nanogaps,nanowires,electrodeposition,plasmon hybridization,etched ion-track membranes,surface plasmons,gold
更新于2025-09-23 15:21:01
-
Loss compensated extraordinary transmission in hybridized plasmonic nanocavities
摘要： Extraordinary optical transmission has been utilized in many optical applications, but the plasmonic losses hinder their full potential. To obtain enhanced transmission, one of the loss compensation methods is to introduce gain. However, an enhanced transmission or even eliminated absorption does not guarantee plasmonic loss compensation. Here, we reveal the distinction between the transmission enhancement mechanisms in gain-assisted plasmonic arrays. To uncover the underlying mechanisms of the modi?ed transmissions, we calculate the e?ective electric permittivity by employing a self-consistent gain model. We demonstrate that a large transmission enhancement in a plasmonic system composed of periodic nanocavities and coaxially placed nanoislands, is led by the loss compensation, which manifests itself as narrowing in e?ective permittivity. In contrast, a slight transmission enhancement in a plasmonic array without the nanoislands arises from the background ampli?cation.
关键词： gain,loss,extraordinary optical transmission,plasmon hybridization,compensation
更新于2025-09-23 15:19:57
-
Self-Organized Conductive Gratings of Au Nanostripe Dimers Enable Tunable Plasmonic Activity
摘要： Plasmonic metasurfaces based on quasi-one-dimensional (1D) nanostripe arrays are homogeneously prepared over large-area substrates (cm2), exploiting a novel self-organized nanofabrication method. Glass templates are nanopatterned by ion beam-induced anisotropic nanoscale wrinkling, enabling the maskless con?nement of quasi-1D arrays of out-of-plane tilted gold nanostripes, behaving as transparent wire-grid polarizer nanoelectrodes. These templates enable the dichroic excitation of localized surface plasmon resonances, easily tunable over a broadband spectrum from the visible to the near- and mid-infrared, by tailoring the nanostripes’ shape and/or changing the illumination conditions. The controlled self-organized method allows the engineering of the nanoantennas’ morphology in the form of Au-SiO2-Au nanostripe dimers, which show hybridized plasmonic resonances with enhanced tunability. Under this condition, superior near-?eld ampli?cation is achievable for the excitation of the hybridized magnetic dipole mode, as pointed out by numerical simulations. The high e?ciency of these plasmonic nanoantennas, combined with the controlled tuning of the resonant response, opens a variety of applications for these cost-e?ective templates, ranging from biosensing and optical spectroscopies to high-resolution molecular imaging and nonlinear optics.
关键词： biosensing,plasmon hybridization,nanostripe dimers,self-organized nanoantennas,transparent nanoelectrodes,large-area metasurfaces,wire-grid polarizers
更新于2025-09-23 15:19:57
-
Tunable local surface plasmon resonance and refractive index sensitivity ability of three-layered dielectric-silver bimetallic nanoshells
摘要： Optical properties and refractive index sensitivity abilities of three-layered silver/gold-dielectric-silver bimetallic nanoshells are investigated based on quasi-static theory. The results show that absorption spectra of silver/gold-dielectric-silver bimetallic nanoshells can be well tuned by changing the inner core radius, middle dielectric radius and outer shell layer thickness. Local surface plasmon resonance (LSPR) shifts of |ω? ?? mode show a red-shift with increasing the inner core radius and the thickness of middle dielectric layer, while a blue-shift with increasing the thickness of outer shell. It is interesting to find that the shifts of |ω+ ?? mode are related to the ratio ε2∕ε4, the component of core and nanoshell. In addition, the refractive index sensitivity abilities of three-layered silver/gold-dielectric-silver bimetallic nanoshells are also reported. A higher refractive index sensitivity ability can be obtained by adjusting its geometric size and component. |ω? ?? mode gets more intensity with increasing the surrounding medium dielectric function, while |ω+ ?? mode fades down. The intensity difference between |ω? ?? mode and |ω+ ?? mode is mainly effected by the surrounding medium dielectric function, its geometric parameter, middle layer dielectric function, the component of core and nanoshell. Our study provides a way to analyze sensitivity application of nanoshells and broadens the application of nanoshells in sensor ability.
关键词： Plasmon hybridization theory,Local surface plasmon resonance (LSPR),Dielectric-silver bimetallic nanoshells,Refractive index sensitivity ability
更新于2025-09-19 17:15:36
-
Electromagnetic field amplification in Al/Ag spherical nanostructures
摘要： The localized electromagnetic field of multilayered nanoshells is studied using quasi-static approach and plasmon hybridization theory. The absorption spectrum of concentric metal–dielectric–metal nanostructures shows three plasmon resonance peaks which are optimized by tuning the geometrical parameters. It has been found that the three-layered nanoshells present different surface plasmon mode when the metal type of inner core and outer shell is exchanged. Silver and aluminum metals have stronger and sharper plasmon modes than that of gold and the outer silver shell has a greater effect on the total plasmonic properties of nanoshell. Three separated plasmon peaks of absorption spectrum of Al–Dielectric–Ag nanoshell cover a wide range from UV to NIR region. In addition, the optimal geometry is discussed to obtain the highest electromagnetic field enhancement in Al–dielectric–Ag nanoshell with special properties.
关键词： Plasmon hybridization theory,SERS,Surface plasmon resonance,Al/Ag spherical nanostructures,Electromagnetic field amplification
更新于2025-09-10 09:29:36
-
Optical Tunability of Silver-Dielectric-Silver Multi-Layered Cylindrical Nanotubes Using Quasi-Static Approximation
摘要： Local surface plasmon resonances (LSPRs) of silver-dielectric-silver multi-layered (SDS-ML) nanotubes are studied by theoretical calculations. Based on quasi-static approximation, the absorption cross section of SDS-ML nanotubes is plotted as a function of wavelength. The results show that SDS-ML nanotubes exhibit strong coupling between the cylindrical silver and nanotubes. The absorption spectra of LSPRs are strongly influenced by changing the radius of the inner core and outer nanotube shell. The longer wavelength is red-shifted by increasing the radius of the inner core and outer shell, while the short wavelength shows the opposite properties. These phenomena are explained by the plasmon hybridization theory. In addition, for clarity, the distributions of electric field intensity at their plasmon resonance wavelengths are also studied.
关键词： Local surface plasmon resonances,quasi-static approximation,silver-dielectric-silver multi-layered nanotubes,plasmon hybridization theory
更新于2025-09-09 09:28:46