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Articles 1 - 13 of 13
Full-Text Articles in Physical Sciences and Mathematics
Dipole Emission Characteristics Near A Topological Insulator Sphere Coated With A Metallic Nanoshell, Huai-Yi Xie, Railing Chang, P. T. Leung
Dipole Emission Characteristics Near A Topological Insulator Sphere Coated With A Metallic Nanoshell, Huai-Yi Xie, Railing Chang, P. T. Leung
Physics Faculty Publications and Presentations
Topological insulators (TI) are quantum states of (2D/3D) matter with an insulating interior but conducting edge/surface states, with these boundary conducting states being protected topologically by time-reversal symmetry. Composite materials of heavy atoms such as Bi2Te3 can be fabricated to show TI properties due to the strong intrinsic spin-orbit coupling of the electrons in these materials. Among the so many intriguing physical properties of these materials, their topological magneto-electric (TME) response is unique and has been studied intensively in the literature, leading to intriguing optical effects such as Faraday and Kerr rotations of incident polarized beams at …
Topological Magnetoelectric Effect As Probed By Nanoshell Plasmonic Modes, Railing Chang, Huai Yi Xie, Ya-Chih Wang, Hai-Pang Chiang, P.T. Leung
Topological Magnetoelectric Effect As Probed By Nanoshell Plasmonic Modes, Railing Chang, Huai Yi Xie, Ya-Chih Wang, Hai-Pang Chiang, P.T. Leung
Physics Faculty Publications and Presentations
Axion electrodynamics is applied to study the response of a plasmonic nanoshell with a core made of topological insulator (TI) materials. The electric polarizability of such a system is calculated in the long wavelength limit via the introduction of two scalar potentials satisfying the various appropriate boundary conditions. Our focus is on the topological magneto-electric effect (TME) as manifested in the coupled plasmonic resonances of the nanoshell. It is found that for a TI with broken time-reversal symmetry, such TME will lead to observable red-shifts in the coupled plasmonic modes, with more significant manifestation of such shifts for the bonding …
Enhanced Terahertz Emission From Quantum Dot By Graphene-Coated Nanoparticle, Edin Sijercic, P. T. Leung
Enhanced Terahertz Emission From Quantum Dot By Graphene-Coated Nanoparticle, Edin Sijercic, P. T. Leung
Physics Faculty Publications and Presentations
The terahertz (THz) emission from quantum dots in close proximity to graphene-coated nanoparticles is studied via phenomenological modeling with particular interest in the possibility of enhancement for such emission via the excitation of the graphene plasmons. It is shown that depending on various factors such as the damping factor and the Fermi level of the graphene, as well as the size and core material of the coated particle, such plasmonic-enhanced THz emission is indeed possible. This thus opens up a new pathway to provide intense THz sources for future applications.
Förster Resonance Energy Transfer Between Molecules In The Vicinity Of Graphene- Coated Nanoparticles, Tingting Bian, Railing Chang, Pui T. Leung
Förster Resonance Energy Transfer Between Molecules In The Vicinity Of Graphene- Coated Nanoparticles, Tingting Bian, Railing Chang, Pui T. Leung
Physics Faculty Publications and Presentations
The recent demonstration of the plasmonic enhanced Förster resonance energy transfer (FRET) between two molecules in the vicinity of planar graphene monolayers is further investigated using graphene-coated nanoparticles (GNP). Due to the flexibility of these nanostructures in terms of their geometric (size) and dielectric (e.g. core material) properties, greater tunability of the FRET enhancement can be achieved employing the localized surface plasmons. It is found that while the typical characteristic graphene plasmonic enhancements are manifested from using these GNP’s, even higher enhancements can be possible via doping and manipulating the core materials. In addition, the broadband characteristics is further expanded …
Surface Plasmons Of A Graphene Parallel Plate Waveguide Bounded By Kerr-Type Nonlinear Media, H. Hajian, A. Soltani-Vala, M. Kalafi, Pui T. Leung
Surface Plasmons Of A Graphene Parallel Plate Waveguide Bounded By Kerr-Type Nonlinear Media, H. Hajian, A. Soltani-Vala, M. Kalafi, Pui T. Leung
Physics Faculty Publications and Presentations
The exact dispersion relations of the transverse magnetic surface plasmons (SPs) supported by a graphene parallel plate waveguide (PPWG), surrounded on one or both sides by Kerr-type nonlinear media, are obtained analytically. It is shown that if self-focusing nonlinear materials are chosen as the surrounding media, the SPs localization length (LL) is decreased, while their propagation length (PL) remains unchanged, as compared to those of a typical graphene PPWG. Moreover, PL and LL of the SPs are considerably affected by adjusting nonlinear parts of the dielectric permittivities of the nonlinear media. It is found that using an appropriate defocusing nonlinear …
Direct Coupling Of Photonic Modes And Surface Plasmon Polaritons Observed In 2-Photon Peem, Robert Campbell Word, Joseph Fitzgerald, Rolf Könenkamp
Direct Coupling Of Photonic Modes And Surface Plasmon Polaritons Observed In 2-Photon Peem, Robert Campbell Word, Joseph Fitzgerald, Rolf Könenkamp
Physics Faculty Publications and Presentations
We report the direct microscopic observation of optical energy transfer from guided photonic modes in an indium tin oxide (ITO) thin film to surface plasmon polaritons (SPP) at the surfaces of a single crystalline gold platelet. The photonic and SPP modes appear as an interference pattern in the photoelectron emission yield across the surface of the specimen. We explore the momentum match between the photonic and SPP modes in terms of simple waveguide theory and the three-layer slab model for bound SPP modes of thin metal films. We show that because the gold is thin (30- 40 nm), two SPP …
Controlled Spatial Switching And Routing Of Surface Plasmons In Designed Single-Crystalline Gold Nanostructures, Rolf Kӧnenkamp, Robert Campbell Word, Joseph Fitzgerald, Athavan Nadarajah, S. D. Saliba
Controlled Spatial Switching And Routing Of Surface Plasmons In Designed Single-Crystalline Gold Nanostructures, Rolf Kӧnenkamp, Robert Campbell Word, Joseph Fitzgerald, Athavan Nadarajah, S. D. Saliba
Physics Faculty Publications and Presentations
Electron emission microscopy is used to visualize plasmonic routing in gold nano-structures. We show that in single-crystalline gold structures reliable routing can be achieved with polarization switching. The routing is due to the polarization dependence of the photon-to-plasmon coupling, which controls the mode distribution in the plasmonic gold film. We use specifically designed, single-crystalline planar structures. In these structures, the plasmon propagation length is sufficiently large such that significant plasmon power can be delivered to the near-field region around the end tips of the router. Solid state devices based on internal electron excitation and emission processes appear feasible.
Photoelectron Emission Control With Polarized Light In Plasmonic Metal Random Structures, Robert Campbell Word, Joseph Fitzgerald, Rolf Kӧnenkamp
Photoelectron Emission Control With Polarized Light In Plasmonic Metal Random Structures, Robert Campbell Word, Joseph Fitzgerald, Rolf Kӧnenkamp
Physics Faculty Publications and Presentations
The authors report on the possibility of switching the emission rate of photoelectrons by polarization changes in the plasmon excitation light. Photoelectron emission is strongly enhanced in the near-field of localized surface plasmons and occurs from areas with typical diameters of 20-70 nm. The underlying physical process involves excitation of a localized surface plasmon polariton with a femtosecond laser pulse, and a subsequent multi-photon photoemission process. The non-linearity of this process leads to a sharp polarization dependence that allows efficient switching of the emission. We demonstrate that a 90° polarization change can result in on/off ratios of ∼100 for electron …
High-Resolution Angular Measurement Using Surface-Plasmon-Resonance Via Phase Interrogation At Optimal Incident Wavelengths, Hai-Pang Chiang, Jing-Lun Lin, Railing Chang, Sheng-Yu Su, P.T. Leung
High-Resolution Angular Measurement Using Surface-Plasmon-Resonance Via Phase Interrogation At Optimal Incident Wavelengths, Hai-Pang Chiang, Jing-Lun Lin, Railing Chang, Sheng-Yu Su, P.T. Leung
Physics Faculty Publications and Presentations
It is demonstrated that ultrahigh-resolution angular measurement can be achieved via surface-plasmon-resonance excitation in which the phase difference between p- and s-polarized reflected waves is monitored as a function of the incidence angle. Resolutions down to 1.9 x 10(-6) deg are obtained by performing the measurements at optimal incident wavelengths. This represents an order of magnitude improvement compared with previously reported values.
Nonlocal Electrodynamic Modeling Of Fluorescence Characteristics For Molecules In A Spherical Cavity, Pui T. Leung, M. H. Hider
Nonlocal Electrodynamic Modeling Of Fluorescence Characteristics For Molecules In A Spherical Cavity, Pui T. Leung, M. H. Hider
Physics Faculty Publications and Presentations
The emission characteristics for molecules in a spherical metallic microcavity are computed using a nonlocal electrodynamic model, based on a theory previously published by Fuchs and Claro [Phys. Rev. B 35, 3722 (1987)] for the multipole polarizability of a sphere. Both radially and tangentially oriented molecules at arbitrary locations inside the cavity are considered, and the results are compared with those from both the local response theory and those for molecules outside a spherical particle. The issue of reciprocity of the solutions for each of the sphere and cavity cases, respectively, is examined in the light of the nonlocal effects. …
The Surface Plasmon Enhancement Effect On Adsorbed Molecules At Elevated Temperatures, P.T. Leung, Hai-Pang Chiang, W. S. Tse
The Surface Plasmon Enhancement Effect On Adsorbed Molecules At Elevated Temperatures, P.T. Leung, Hai-Pang Chiang, W. S. Tse
Physics Faculty Publications and Presentations
The surface plasmon enhancement effect on adsorbed molecules at elevated substrate temperatures is studied theoretically using surface enhanced Raman scattering (SERS) as an example. The surface structure is idealized to be a monodisperse spherical particle with its nonlocal dielectric response accounted for. The temperature effects are modeled using a temperature-dependent collision frequency in the Drude model. Numerical results show that only a small decrease in the SERS enhancement ratio occurs for temperatures up to the melting point of the substrate, even for scattering close to the surface plasmon resonance frequency of the metal. More definitive results are subjected to more …
Surface-Enhanced Raman Scattering At Elevated Temperatures, P.T. Leung, M. H. Hider, Erik J. Sánchez
Surface-Enhanced Raman Scattering At Elevated Temperatures, P.T. Leung, M. H. Hider, Erik J. Sánchez
Physics Faculty Publications and Presentations
The effect on surface-enhanced Raman scattering due to the increase in temperature of the metallic substrate is studied via a simple model for physisorbed molecules. Surface roughness is represented by a spherical or spheroidal island, and the temperature effects on the surface plasmon are accounted for via a slightly modified Ujihara model. It is found that the enhancement ratio in general decreases as substrate temperature increases. For noble metals like silver, this temperature effect is particularly pronounced at scattering frequencies close to that of the surface-plasmon resonance; and for frequencies well below the surface plasmon frequency, the enhancement ratio is …
Decay Of Molecules At Corrugated Thin Metal Films, P.T. Leung, Young Sik Kim, Thomas F. George
Decay Of Molecules At Corrugated Thin Metal Films, P.T. Leung, Young Sik Kim, Thomas F. George
Physics Faculty Publications and Presentations
The problem of the decay rate for molecules at corrugated thin metal films is considered theoretically via a classical phenomenological approach by generalization of a previous theory for a single rough surface. In particular, numerical results are worked out in detail for grating films with various possible arrangements of the two grating surfaces, and for both cases with a supported and a free-standing film. Effects due to cross coupling into the long- and short-range surface plasmons are observed, and correlations to recent experiments performed by Gruhlke, Holland, and Hall are made. It is suggested that fluorescence experiments with pulsed-laser excitations …