Two devices for subwave length focusing of light are explored. The first one is a thin film of a well reflecting metal which the converging beam of surface plasmons with a wave number $h>>ω_0/c$ is excited on. The waist of this beam has a cross section that is much smaller than $λ_0^2$. The second device is a linear nanoantenna with a gap in the middle. A resonance plasmon is excited in the antenna. The field in the gap concentrates on the spot that is much smaller than $λ_0^2$. In both cases the effect of field enhancement in the spot of subwave length focusing is greatly decreased because of propagation losses in the first case and because of a small excitation cross section in the second case. It is suggested to improve on the effect of excitation of the film and the nanoantenna by means of interaction with an adjacent atom or quantum dot.
Using transmission electron microscopy (TEM) to analyse the physical-chemical surface properties of subwavlength structured silver films and finite-difference time-domain (FDTD) numerical simulations of the optical response of these structures to plane-wave excitation, we report on the origin and nature of the persistent surface waves generated by a single slit-groove motif and recently measured by far-field optical interferometry. The surface analysis shows that the silver films are free of detectable oxide or sulfide contaminants, and the numerical simulations show very good agreement with t…
Measurement of the transmitted intensity from a coherent monomode light source through a series of subwavelength slit arrays in Ag films, with varying array pitch and number of slits, demonstrate enhancement (suppression) by as much as a factor of 6 (9) when normalized to that of an isolated slit. Pronounced minima in the transmitted intensity were observed at array pitches corresponding to lambda_SPP, 2lambda_SPP, and 3lambda_SPP where lambda_SPP is the wavelength of the surface plasmon polariton (SPP). Increasing the number of slits to more than four does not increase appreciably the per-sli…
Tightly confined plasmon waveguide modes supported by semicircular cross section top silver nanoridges are investigated in this paper. Mode field profiles, dispersion curves, propagation distances, confinement factors, and figure-of-merits of semicircular top silver nanoridge plasmon waveguide mode are calculated for different radii of curvature at different wavelengths. It is found that semicircular top silver nanoridges support tightly confined quasi-TEM plasmon waveguide modes. Semicircular top silver nanoridge mode has longer propagation distance and higher figure-of-merit than that of the…
We present angle- and polarization-resolved measurements of the optical transmission of a subwavelength hole array. These results give a (far-field) visualization of the corresponding (near-field) propagation of the excited surface plasmons and allow for a simple analysis of their polarization properties.
We investigate the transmission of focused beams through single subwavelength holes in a silver film. We use radially and azimuthally polarized light, respectively, to excite higher order waveguide modes as well as to match the radial symmetry of the aperture geometry. Remarkably, the transmission properties can be described by a classical waveguide model even for thicknesses of the silver film as thin as a quarter of a wavelength.
Surface plasmon polaritons scattering from 2D subwavelength silicon wires is investigated using finite difference time domain method. It is shown that coupling an incident surface plasmon polariton to inter-cavity modes of the particle can dramatically changes transmitted fields and plasmon induced forces. In particular, both transmission and optical forces are highly sensitive to the particle size that is related to the excitation of whispering gallery modes or standing-wave modes depending on the particle shape and size. This features might have potential sensing applications.
Mid-infrared photonic modes of a periodically patterned metal-dielectric-metal structure have been investigated theoretically and experimentally. We have observed an anticrossing behaviour between cavity modes localized in the double-metal regions and the surface plasmon polariton, signature of a hybridisation between the two modes.
We analyze, by means of numerical simulations, transmission enhancements through sub- wavelength slits due to the presence of sets of plasmonic nanocylinders, placed near the exit of these apertures. Further, we extend this study to photonic crystals of dipolar plasmonic particles in front of an array of extraordinarily transmitting slits practiced in a metallic slab.
Polarization dependence of the exciton-plasmon-photon conversion in silver nanowire-quantum dots structure was investigated using a scanning confocal microscope system. We found that the fluorescence enhancement of the CdSe nanocrystals was correlated with the angle between the excitation light polarization and the silver nanowire direction. The polarization of the emission was also related with the nanowire direction. It was in majority in the direction parallel with nanowire.
The propagation of plasmonic waves in various metallic quantum nanostructures have considered attention for their applications in technology. The quantum plasmonic properties of metallic nanostructures in the quantum size regime have been difficult to describe by an appropriate model. Here the nonlocal quantum plasmons are investigated in the most important metals of copper, gold, and silver. Dispersion properties of these metals and propagation of longitudinal quantum plasmons in the high photon energy regime are studied by a new model of nonlocal quantum dielectric permittivity. The epsilon …
Multiple surface plasmon-polariton (SPP) waves excited at the interface of a homogeneous isotropic metal and a chiral sculptured thin film (STF) impregnated with silver nanoparticles were theoretically assessed for the multiple-SPP-waves-based sensing of a fluid uniformly infiltrating the chiral STF. The Bruggemann homogenization formalism was used in two different modalities to determine the three principal relative permittivity scalars of the silver-nanoparticle-impregnated chiral STF infiltrated uniformly by the fluid. The dynamic sensitivity increased when silver nanoparticles were present…
Hotspots of surface-enhanced resonance Raman scattering (SERRS) are localized within 1 nm at gaps or crevices of plasmonic nanoparticle (NP) dimers. We demonstrate SERRS hotspots with volumes that are extended in one dimension tens of thousand times compared to standard zero-dimensional hotspots using gaps or crevices of plasmonic nanowire (NW) dimers.
Propagating two-dimensional plasmon modes guided by elliptical cross section silver nanoridges are investigated in this paper. Mode field profiles, dispersion curves, propagation distances, and figure-of-merits of the plasmon ridge modes are calculated for various elliptical cross sections. It is found that an elliptical cross section metal nanoridge, if designed properly, can support a well-confined plasmon mode with a longer propagation distance and a higher figure-of-merit than the flat-top nanoridge plasmon waveguide of the same width. The optimal ridge waveguide cross section is obtained …
Plasmon mode in a silver nanowire is theoretically studied when the nanowire is placed on or near a silica substrate. It is found that the substrate has much influence on the plasmon mode. For the nanowire on the substrate, the plasmon (hybrid) mode possesses not only a long propagation length but also an ultrasmall mode area. From the experimental point of view, this cavity-free structure holds a great potential to study a strong coherent interaction between the plasmon mode and single quantum system (for example, quantum dots) embedded in the substrate.
Propagating two-dimensional plasmon modes guided along silver nanoridge waveguides with triangular and inverted triangular cross sections are investigated in this paper. Mode field profiles, dispersion curves, propagation distances, and figure-of-merits of the plasmon ridge modes are calculated for silver nanoridge waveguides with various triangular and inverted triangular waveguide cross sections. It is found that the triangular cross section nanoridge waveguide, if designed properly, can have longer propagation distance and higher figure-of-merit than the flat-top nanoridge waveguide of the …
Absorbing and emitting optical properties of a spherical plasmonic nanoantenna are described in terms of the size dependent resonance frequencies and damping rates of the multipolar surface plasmons (SP). We provide the plasmon size characteristics for gold and silver spherical particles up to the large size retardation regime where the plasmon radiative damping is significant. We underline the role of the radiation damping in comparison with the energy dissipation damping in formation of receiving and transmitting properties of a plasmonic particle. The size dependence of both: the multipolar…
Using propagating surface plasmons (SPs) on silver nanowire (NW), we demonstrate that focused laser light at the end of silver nanowire can excite single quantum dot (QD) microns away from the excitation spot. The QD-NW interaction allows the excited QD convert part of its energy into propagating SPs which then can be detected at the remote sites. Simultaneous multi-QDs remote-excitation and detection are also realized. Furthermore, the tight confinement of propagating SPs around the NW surface enables selective excitation of QDs very close in space, which cannot be realized under conventional…
We report the fabrication of triangular lattices of parallel gold and silver nanowires of high optical quality, with diameters down to 500 nm and length-to-diameter ratios as high as 100,000. The nanowires are supported by a silica glass matrix and are disposed around a central solid glass core, i.e., a missing nanowire. These cm-long structures make it possible to trap light within an array of nanowires and characterize the plasmon resonances that form at specific optical frequencies. Such nanowire arrays have many potential applications, e.g., to imaging on the sub-wavelength scale.
By using a self-consistent Maxwell-Bloch method, we demonstrate the simultaneously lasing and spasing behavior in a simple metal grating-film nanostructure, which can be attributed to spatial hole burning and the gain competition of different modes at the band edge and in the plasmonic band gap. We show three modes: one spaser mode in gap with quality factor as high as 248.54, one plasmon lasing mode at band edge which emit vertically from the grating surface, and the other plasmon lasing mode at band edge which is suppressed by the spaser mode. This method may find significant applications in…
We investigate surface plasmon modes supported by flat-top silver nano-ridges. We calculate the mode electromagnetic field distribution, the dispersion curve, the travel range, and the figure-of-merit of the nano-ridge mode. We find that the nano-ridge surface plasmon modes are quasi-TEM modes with longitudinal field components three orders of magnitude smaller than the transverse field components. The quasi-TEM nature of mode profiles reveals that the propagation of free electron oscillations on the top of the nano-ridge contributes mainly to the tightly confined ridge mode. We also find that…
Extraordinary transmission through subwavelength metallic apertures has been extensively studied and demonstrated. At resonance, the coupling between surface plasmons on both surfaces of the metallic film tunnels the photon from the one side to the other through the subwavelength aperture with small transmission efficiency based on the metals dielectric parameters and aperture geometrical dimensions. Here, we report a completely different form of extraordinary transmission, where the two subwavelength complementary apertures when coupled with an optical cavity induce about 100% extraordinary t…
We proposed an experimentally feasible scheme of nano-plamonic switch and quantum router via the single self-assembled InGaAs/GaAs semiconductor quantum dot (SQD) with a V type three-level energy structure located between two silver metallic waveguides. We studied theoretically transmission and transfer rates of single plasmons in such a multi-ports system via the real-space approach, where our results showed that single plasmons from the input port could be switchable and redirected by controlling parameters, such as the intensity of the classical field, the detunings, and the interaction bet…
This commentary aims to expose the fallacy of claiming that a plasmonic silver film superlens is capable to image real subwavelength objects. This lens was proposed by the Berkeley's group who, in their misleading experiment, inappropriately regarded subwavelength apertures as the objects to be imaged whereas the main function of these apertures was to transform free space laser light into an evanescent field necessary for exciting the surface plasmon resonance phenomenon in silver. In addition, the apertures also determined the constrained effective area on the silver film where the phenomeno…
Metal-dielectric interfaces of various geometries are fundamental photonic material platforms for surface plasmons. Surface plasmon polaritons and localized surface plasmons are two surface plasmon modes that are excited on planar and curved metal-dielectric interfaces, respectively. Herein, we demonstrate in-situ formation of silver nanoparticles by diffusion at a planar interface between sputter-deposited silver and nitride dielectrics. In one step, we synthesize a nanostructure that exhibits both localized surface plasmon resonances at silver nanoparticles and surface plasmon resonances at …
We report the coupling of photons from an optical fiber taper to surface plasmon modes of silver nanowires. The launch of propagating plasmons can be realized not only at ends of the nanowires, but also at the midsection. The degree of the coupling can be controlled by adjusting the light polarization. In addition, we present the coupling of light into multiple nanowires from a single optical fiber taper simultaneously. Our demonstration offers a novel method for optimizing plasmon coupling into nanoscale metallic waveguides and promotes the realization of highly integrated plasmonic devices.
Real-time surface plasmon polariton propagation in silver nanowires
Max-Born-Institut（马克斯·伯恩研究所）；Humboldt-Universität zu Berlin（柏林洪堡大学）；Center for the Science of Materials Berlin, Humboldt-Universität zu Berlin（柏林材料科学中心，柏林洪堡大学）；Helmholtz-Zentrum Berlin for Materials and Energy（柏林亥姆霍兹材料与能源中心）；Friedrich-Schiller-University（弗里德里希·席勒大学）
We report on measurements of visible extinction spectra of semicontinuous silver nanoshells grown on colloidal silica spheres. We find that thin, fractal shells below the percolation threshold exhibit geometrically tunable plasmon resonances. A modified scaling theory approach is used to model the dielectric response of such shells, which is then utilized to obtain the extinction cross section in a retarded Mie scattering formalism. We show that such spherical resonators support unique plasmon dynamics: in the visible there is a new regime of coherently driven cluster-localized plasmons, while…
Subwavelength resonators, ranging from single atoms to metallic nanoparticles, typically exhibit a narrow-bandwidth response to optical excitations. We computationally design and experimentally synthesize tailored distributions of silver nanodisks to extinguish light over broad and varied frequency windows. We show that metallic nanodisks are two-to-ten-times more efficient in absorbing and scattering light than common structures, and can approach fundamental limits to broadband scattering for subwavelength particles. We measure broadband extinction per volume that closely approaches theoretic…
Subwavelength resonators, ranging from single atoms to metallic nanoparticles, typically exhibit a narrow-bandwidth response to optical excitations. We computationally design and experimentally synthesize tailored distributions of silver nanodisks to extinguish light over broad and varied frequency windows. We show that metallic nanodisks are two-to-ten-times more efficient in absorbing and scattering light than common structures, and can approach fundamental limits to broadband scattering for subwavelength particles. We measure broadband extinction per volume that closely approaches theoretic…
We demonstrate surface plasmon-induced enhancements in optical imaging and spectroscopy on silver coated silicon nanocones which we call black silver substrate. The black silver substrate with dense and homogeneous nanocone forest structure is fabricated on wafer level with a mass producible nanomanufacturing method. The black silver substrate is able to efficiently trap and convert incident photons into localized plasmons in a broad wavelength range, which permits the enhancement in optical absorption from UV to NIR range by 12 times, the visible fluorescence enhancement of ~30 times and the …
Plasmonic nano structures such as wire waveguides or antennas are key building blocks for novel highly integrated photonics. A quantitative understanding of the optical material properties of individual structures on the nanoscale is thus indispensable for predicting and designing the functionality of complex composite elements. In this letter we study propagating surface plasmon polaritons in single silver nanowires isolated from its environment by levitation in a linear Paul trap. Symmetry-breaking effects, e.g., from supporting substrates are completely eliminated in this way. Illuminated w…
We present a numerical study and analytical model of the optical near-field diffracted in the vicinity of subwavelength grooves milled in silver surfaces. The Green's tensor approach permits computation of the phase and amplitude dependence of the diffracted wave as a function of the groove geometry. It is shown that the field diffracted along the interface by the groove is equivalent to replacing the groove by an oscillating dipolar line source. An analytic expression is derived from the Green's function formalism, that reproduces well the asymptotic surface plasmon polariton (SPP) wave as we…
We demonstrate a simple and high-performance laser-assisted technique for silver nanoring fabrication, which includes the ablation of the Ag film by focused nanosecond pulses and subsequent reactive ion polishing. The nanoring diameter and thickness can be controlled by optimizing both the pulse energy and the metal film thickness at laser ablation step, while the subsequent reactive ion polishing provides the ability to fabricate the nanoring with desirable height. Scattering patterns of s-polarized collimated laser beam obliquely illuminating the nanoring demonstrate the focal spot inside th…
Plasmonic circuitry is considered as a promising solution-effective technology for miniaturizing and integrating the next generation of optical nano-devices. A key element is the shared metal network between electrical and optical information enabling an efficient hetero-integration of an electronic control layer and a plasmonic data link. Here, we investigate to what extend surface plasmons and current-carrying electrons interfere in such a shared circuitry. By synchronously recording surface plasmon propagation and electrical output characteristics of single chemically-synthesized silver nan…
We report on the creation of angle-independent colors on silver using closely time-spaced laser bursts. The use of burst mode, compared to traditional non-burst is shown to increase the Chroma (color saturation) by ~50% and to broaden the lightness range by up to ~60%. Scanning electron microscope analysis of the surfaces created using burst mode, reveal the creation of 3 distinct sets of laser induced periodic surface structures (LIPSS): low spatial frequency LIPSS (LSFL), high spatial frequency LIPSS (HSFL) and large laser-induced periodic surface structures (LLIPSS) that are 10 times the la…
We demonstrate propagation of plasmons in single crystalline silver nanostructures fabricated using a combination of a bottom-up and a top-down approach. Silver nanoplates of thickness around 65 nm and a surface area of about 100 μm^2 are made using a wet chemical method. Silver nanotips and nanowires are then sculptured by focused ion beam milling. The plasmons are excited by using the fluorescence from the redeposited silver clusters during the milling process. Propagation of plasmons in the nanowires is observed in the visible spectral region. We also observe a cavity effect by measuring th…
The resonance effects on the optical second harmonic generation from 140 nm silver nanoparticles is studied experimentally by hyper-Rayleigh scattering and numerically by finite element method calculations. We find that the interferences between the broad dipolar and narrow octupolar surface plasmon resonances leads to nonlinear Fano profiles that can be externally controlled by the incident polarization angle. These profiles are responsible for the nonlinear plasmon-induced transparency in the second harmonic generation.
This study investigated spectral changes in the absorption cross-sections of single strong coupling systems composed of single silver nanoparticle dimers and a few dye molecules during the quenching of surface-enhanced resonant Raman scattering (SERRS). The absorption cross-section was obtained by subtracting the scattering cross-section from an extinction cross-section. The spectral changes in these cross-sections were evaluated using a classical hybridization model composed of a plasmon and a molecular exciton including a molecular multi-level property. The changes in the scattering and exti…
Plasmonic waveguides are key elements in nanophotonic devices serving as optical interconnects between nanoscale light sources and detectors. Multimode operation in plasmonic two-wire transmission lines promises important degrees of freedom for near-field manipulation and information encoding. However, highly confined plasmon propagation in gold nanostructures is typically limited to the near-infrared region due to ohmic losses, excluding all visible quantum emitters from plasmonic circuitry. Here, we report on top-down fabrication of complex plasmonic nanostructures in single-crystalline silv…
We present an electron energy loss study using energy filtered TEM of spatially resolved surface plasmon excitations on a silver nanorod of aspect ratio 14.2 resting on a 30 nm thick silicon nitride membrane. Our results show that the excitation is quantized as resonant modes whose intensity maxima vary along the nanorod's length and whose wavelength becomes compressed towards the ends of the nanorod. Theoretical calculations modelling the surface plasmon response of the silver nanorod-silicon nitride system show the importance of including retardation and substrate effects in order to describ…
Enhanced transmissions through a gold film with arrays of subwavelength holes are theoretically studied, employing the rigid full vectorial three dimensional finite difference time domain method. Influence of air-holes shape to the transmission is firstly studied, which confirms two different resonances attributing to the enhanced transmission: the localized waveguide resonance and periodic surface plasmon resonances. For the film coated with dielectric layers, calculated results show that in the wavelength region of interest the localized waveguide resonant mode attributes to sensing rather t…
We investigate the propagation of surface-enhanced resonant Raman scattering (SERRS) light by several micrometers through a one-dimensional hotspot (1D HS) located between a plasmonic nanowire dimer (NWD). The propagation exhibits the properties, e.g. an effective propagation induced by excitation and detection polarization orthogonal to the 1D HS long axis, the propagation profiles composed of bright short and dark long propagations, SERRS spectral shapes independent of localized plasmon (LP) resonance of NWDs, redshifts in the SERRS spectra at the edges of 1D HSs, and considerable NWD-by-NWD…
We present an optical investigation of surface plasmon polaritons propagating along nanoscale Au-wires, lithographically defined on GaAs substrates. A two-axis confocal microscope was used to perform spatially and polarization resolved measurements in order to confirm the guiding of surface plasmon polaritons over lengths ranging from $5-20 μm$ along nanowires with a lateral dimension of only $\approx 100 nm$. Finite difference time domain simulations are used to corroborate our experimental observations and highlight the potential to couple proximal quantum dot emitters to propagating plasmon…
We propose and analyze a family of nanoscale cavities for electrically-pumped surface-emitting semiconductor lasers that use surface plasmons to provide optical mode confinement in cavities which have dimensions in the 100-300 nm range. The proposed laser cavities are in many ways nanoscale optical versions of micropatch antennas that are commonly used at microwave/RF frequencies. Surface plasmons are not only used for mode confinement but also for output beam shaping to realize single-lobe far-field radiation patterns with narrow beam waists from subwavelength size cavities. We identify the c…
Using a random array of coupled metallic nanowires as a generic example of disordered plasmonic systems, we demonstrate that the structural disorder induces localization of light in these nanostructures at a deep-subwavelength scale. The ab initio analysis is based on solving the complete set of 3D Maxwell equations. We find that random variations of the radius of coupled plasmonic nanowires are sufficient to induce the Anderson localization (AL) of surface-plasmon polaritons (SPPs), the size of these trapped modes being significantly smaller than the wavelength. Remarkably, the optical-gain c…
We demonstrate an unexpectedly strong surface-plasmonic absorption at the interface of silver and high-index dielectrics based on electron and photon spectroscopy. The measured bandwidth and intensity of absorption deviate significantly from the classical theory. Our density-functional calculation well predicts the occurrence of this phenomenon. It reveals that due to the low metal-to-dielectric work function at such interfaces, conduction electrons can display a drastic quantum spillover, causing the interfacial electron-hole pair production to dominate the decay of surface plasmons. This fin…
The morphology of a columnar thin film (CTF) of silver renders it an effectively biaxially anisotropic continuum. CTFs of silver deposited on one-dimensional gratings of photoresist showed strong blazing action and asymmetrically coupled optical radiation to surface plasmon-polariton (SPP) waves propagating only along one direction supported by either the CTF/photoresist or the CTF/air interfaces. Homogenization of the CTFs using the Bruggeman formalism revealed them to display hyperbolic dispersion, and the dispersion of SPP waves was adequately described thereby.
Using a holographic approach, we experimentally study the near-field intensity distribution of light squeezed through an isolated subwavelength plasmonic hole in a thin metallic film. Our experiments revealed an in-plane electric dipole moment excited near the isolated hole. By analyzing the fringe patterns formed between the in-plane dipole and plane wave illumination, both the transmission coefficient and phase shift of the dipole can be retrieved. We also observed opposite phases of the excited dipoles from the subwavelength dent and protrusion in the metallic film, in good agreement with t…
We report on the first experimental demonstration that the microstructure based on a dielectric cuboid combined to a thin metal film can act as an efficient plasmonic lens allowing focusing surface plasmons in a subwavelength scale. By means of numerical simulation of surface plasmon-polariton (SPP) field intensity distributions in the microstructure, we observe a low divergence of plasmonic photonic jet (PPJ) and high intensity subwavelength spots at the communication wavelength of 1530 nm. Then we fabricate an experimental sample of the microstructure and study the SSP field intensity distri…
The effect of the tilt angle of metal film on the transmissivity of subwavelength holes in optically thick metal film is investigated. The transmission efficiency is found can be highly dependent on the tilt angle. It is also found that when the input photons are polarized not along the eigenmode directions of surface plasmon polariton, a birefringent phenomenon is observed when the array with periodic of subwavelength holes is tilted. Linear polarization states can be changed to elliptical polarization states and a phase can be added between two eigenmodes. The phase is changed with the tilt …
Optical binding allows creation of mechanically stable nanoparticle configurations owing to formation of self-consistent optical trapping potentials. While the classical diffraction limit prevents achieving deeply subwavelength arrangements, auxiliary nanostructures enable tailoring optical forces via additional interaction channels. Here, a dimer configuration next to metal surface was analyzed in details and the contribution of surface plasmon polariton waves was found to govern the interaction dynamics. It was shown that the interaction channel, mediated by resonant surface waves, enables a…
In this Comment I discuss two incorrect statements which were made in the paper "Silver nanoparticle array structures that produce remarkably narrow plasmon line shapes" [J. Chem. Phys.120, 10871 (2004)] by Zou, Janel, and Schatz (ZJS). The first statement is about the use of quasistatic approximation in my earlier work on the similar subject, and the second statement concerns the possibility of exact cancellation of radiative relaxation in periodical chains of nanoparticles. The relationship between the quasistatic approximation, the dipole approximation, and the approximation due to Doyle [P…
We study the surface plasmon modes in a silver double-nanowire system by employing the eigenmode analysis approach based on the finite element method. Calculated dispersion relations, surface charge distributions, field patterns and propagation lengths of ten lowest energy plasmon modes in the system are presented. These ten modes are categorized into three groups because they are found to originate from the monopole-monopole, dipole-dipole and quadrupole-quadrupole hybridizations between the two wires, respectively. Interestingly, in addition to the well studied gap mode (mode 1), the other m…
Fundamental understanding of the light-matter interaction in the context of nano-particles is immensely bene- fited by the study of geometry dependent tunable Localized Surface Plasmon Resonance (LSPR) and has been demonstrated to have potential applications in various areas of science. The polarization characteristics of LSPR in addition to spectroscopic tuning can be suitably exploited in such systems as contrast enhancement mech- anisms and control parameters. Such polarization characteristics like diattenuation and retardance have been studied here using a novel combination of Muller-matri…
The enhanced light transmission through an array of subwavelength holes surrounded by Bragg mirrors is studied, showing that the mirrors act to confine the surface plasmons associated with the Extraordinary Optical Transmission effect, forming a surface resonant cavity. The overall effect is increased light transmission intensity by more than a factor of three beyond the already enhanced transmission, independent of whether the Bragg mirrors are on the input or the output side of the incident light. The geometry of the Bragg mirror structures controls the enhancement, and can even reduce the t…
In electron energy-loss spectroscopy (EELS) of individual silver nanoparticles encapsulated in silicon nitride, we observe besides the usual dipole resonance an additional surface plasmon (SP) resonance corresponding to higher angular momenta. We even observe both resonances for nanoparticle radii as small as 4 nm, where previously only the dipole resonance was assumed to play a role. Electron beams positioned outside of the particles mostly excite the dipole mode, but the higher-order resonance can even dominate the dipole peak when exciting at the particle surface, the usual choice for maxim…
The concepts of spoof surface plasmon polaritons and adiabatic field compression are employed to design metallic near-field probes that allow guiding and focusing of mid-infrared wavelength electromagnetic radiation and provides subwavelength field confinements and a lateral optical resolution of about 10 nm.
