Effects of Surface Plasmon Coupling on the Whispering-Gallery Resonance in a Hexagonal Nanowire Cavity Structure

Plasmonics - The effects of surface plasmon (SP) coupling with the excitation radiating dipole on the behaviors of the whispering-gallery resonance (WGR) modes in a hexagonal GaN nanowire cavity...     

Imaging of Surfaces by Concurrent Surface Plasmon Resonance and Surface Plasmon Resonance-Enhanced Fluorescence

Surface plasmon resonance imaging and surface plasmon induced fluorescent are sensitive tools for surface analysis. However, existing instruments in this area have provided limited capability for concurrent detection, and may be large and expensive. We demonstrate a highly cost-effective system capable of concurrent surface plasmon resonance microscopy (SPRM) and surface plasmon resonance-enhanced fluorescence (SPRF) imaging, allowing for simultaneous monitoring of reflectivity and fluorescence from discrete spatial regions. The instrument allows for high performance imaging and quantitative measurements with surface plasmon resonance, and surface plasmon induced fluorescence, with inexpensive off-the-shelf components.     

Dispersion and Damping of Gold Surface Plasmon

High-resolution electron energy loss spectroscopy was used to investigate the surface plasmon dispersion in (111)-oriented Au films grown on Cu(111). The measured dispersion of the plasmon mode was positive, as found for Ag. The centroid of the induced charge associated to the plasmon field lies well inside the jellium edge. The damping relation of the Au surface plasmon presented a critical wave vector of 0.11 Å^?1. For higher values of the parallel momentum transfer, the line width of Au surface plasmon considerably increased as a consequence of the opening of a new decay channel via single-particle transitions.     

Liquid Crystal-Based Surface Plasmon Resonance Biosensor

Plasmonics - Surface plasmon resonance has many applications in designing biosensors. In this paper, an easy fabrication liquid crystal-based surface plasmon resonance (LC-SPR) biosensor is...     

Bragg-Scattered Surface Plasmon Microscopy: Theoretical Study

We present a new approach to surface plasmon microscopy with high refractive index sensitivity and spatial resolution that is not limited by the propagation length of surface plasmons. It is based on a nanostructured metallic sensor surface supporting Bragg-scattered surface plasmons. We show that these non-propagating surface plasmon modes are excellently suited for spatially resolved observations of refractive index variations on the sensor surface owing to their highly confined field profile perpendicular to as well as parallel to the metal interface. The presented theoretical study reveals that this approach enables reaching similar refractive index sensitivity as regular surface plasmon resonance (SPR) microscopy and offers the advantage of improved spatial resolution when observing dielectric features with lateral size <10???m for the wavelength around 800?nm and gold as the SPR-active metal. This paper demonstrates the potential of Bragg-scattered surface plasmon microscopy for high-throughput SPR biosensing with high-density microarrays.     

Nano-gap-Enhanced Surface Plasmon Resonance Sensors

This paper analyzes how dual-mode surface plasmon resonance sensors can be further improved if one were to introduce small (∼20 nm) gaps in the film surface. First, a figure of merit, the sensor’s limit of detection (LOD), is defined in order to optimize the design of the nano-gap sensor. Secondly, the LOD of this design is compared with that of an optimized planar dual-mode design. Through this analysis, it is shown that the LOD of the planar sensor can be improved upon by around a factor of 7 when compared with the nano-gap-enhanced design. Furthermore, with the nano-gap design, the lower wavelength plasmon mode demonstrates remarkably improved selectivity when compared with the conventional sensor. In order to explain these results, the dispersion of each plasmon mode along with the electromagnetic field profiles are modeled and analyzed.     

Lifetime of Enhanced Graphene Surface Plasmon and Superstrate Sensitivity

Plasmonics - We investigated the field enhancement and lifetime of tuning surface plasmon in zero-thickness nanostructured graphene patches. The graphene surface plasmon (GSP) resonance mechanism...     

Aluminum-Based Deep-Ultraviolet Surface Plasmon Resonance Sensor

Plasmonics - An aluminum-based deep-ultraviolet surface plasmon resonance (DUV-SPR) sensor is promising for biological applications. Design aspects of a DUV-SPR sensor are here considered by using...     

Multiple-Beam Surface Plasmon Holographic Nanolithography

Multiple-beam surface plasmon holographic nanolithography based on a hemispherical prism coupling configuration is numerically studied in this paper. The proposed configuration is systematically analyzed and optimized for the purpose of achieving five different two-dimensional Bravais lattices by means of adjusting the spatial distribution of three incident beams properly. Furthermore, it is shown that the variation in the relative phase between incident beams can give rise to rich periodic patterns when overlapping more than three beams for surface plasmon holographic nanolithography.     

Long-Range Surface Plasmon Supported by Asymmetric Bimetallic Structure

With this study, we prove that an asymmetric bimetallic structure can support long-range surface plasmon (LRSP) and propose a procedure for its optimization. By applying different criteria we prove that the plasmon which is supported by the structure is indeed LRSP. Unlike all known asymmetric structures supporting LRSP, our structure provides prism excitation and can be used as a biochip for biosensing. Moreover, we show that the structure supports a plasmon with the same propagation constant as LRSP and which is excited at the interface of metal and buffer. This plasmon can be used as a reference channel providing information for the temperature of the structure.     

InGaN/GaN MQW Photoluminescence Enhancement by Localized Surface Plasmon Resonance on Isolated Ag Nanoparticles

Spectroscopic study of photoluminescence (PL) enhancement due to the coupling of the light emitters in InGaN/GaN multiple quantum wells (MQWs) with the localized surface plasmon (LSP) resonance on silver (Ag) nanoparticles (NPs) is performed using the confocal microscopy and scanning near-field optical microscopy (SNOM) techniques. The paper is focused on revealing the emission enhancement due to coupling with a single metal nanoparticle. The enhancement is confirmed by time-resolved study of differential transmission (DT). The enhancement suppression caused by potential fluctuations due to the variations of indium content and quantum well (QW) width is also studied. A strong photoexcitation intensity dependence of the emission enhancement due to spectral runaway of the MQW emission from the resonance as carrier density increases is observed both in spatially integrated spectra and in the vicinity of a single nanoparticle.     

Impedance-Matching Surface Plasmon Absorber for FDTD Simulations

The perfectly matched layer (PML) can be used as an excellent boundary in the finite-difference time-domain method; however, it fails to absorb surface plasmon (SP) wave directly. In order to absorb an incident SP wave at the edge of a metal surface, an impedance-matching layer (IML) is implemented between the metal surface and the PML. A very low SP wave reflectance of −26.54 dB is achieved through the use of an IML with a length of only λ/3. The IML significantly reduces SP wave reflectance and creates a quasi-infinite regime for the purpose of SP wave propagation on the metal’s surface while the acquired simulation area undergoes a slight increase.     

Theoretical Assessment of Localized Surface Plasmon Resonance Properties of Au-Interlayer-Ag Multilayered Nanoshells

Plasmonics - The localized surface plasmon resonance (LSPR) properties of Au-interlayer-Ag multilayered nanoshells are studied by discrete dipole approximation (DDA) and plasmon hybridization...     

Nanostructuring of Continuous Gold Film by Laser Radiation Under Surface Plasmon Polariton Resonance Conditions

The physical mechanisms of metallic nanoparticles formation by laser technology were studied. The system air/Au film/glass was irradiated by laser at the conditions of surface plasmon resonance. A surface electromagnetic wave was excited in Kretchmann configuration by the fundamental and second harmonics of the Q-switched YAG/Nd⁺³ laser with pulse power density close to the threshold of melting. Nanostructuring of Au film was observed only for the second harmonic (λ = 0.532 μm) irradiation at the surface plasmon polariton resonance (SPR) conditions. Estimations were done using the interference model of the differently directed plasmon polariton waves excited by a surface electromagnetic wave on the metal surface. It was shown that a regular pattern of locally heated spots can be formed in a metallic film by pulsed laser irradiation. The spatial distribution of this pattern is close to the period of interference. The observed effect of laser nanofragmentation is explained by the self-organization of plasmon polariton subsystem in the process of Au nanoparticles formation at high laser intensity levels. These methods open new possibilities for nanostructured surfaces formation utilizing simple self-organization processes.     

Sensitivity Enhancement of Surface Plasmon Resonance Biosensor with 2-D Franckeite Nanosheets

Plasmonics - The sensitivity of a standard surface plasmon resonance (SPR) biosensor in angular interrogation is low. A unique 2-dimensional substantial heterostructure, franckeite/graphene layer,...     

Compact Color Filter and Polarizer of Bilayer Metallic Nanowire Grating Based on Surface Plasmon Resonances

Surface plasmon resonances on bilayer aluminum nanowire gratings are studied in both theory and experiment. It is found that there are two kinds of surface plasmon on the bilayer metallic gating: longitudinal aluminum/dielectric/aluminum slit and lateral aluminum/dielectric interface waveguide mode. The surface plasmon waveguide mode resonance in the slits makes the grating act as a transverse magnetic (TM)-passing polarizer. With the lateral waveguide mode resonance, certain wavelengths of the incident TM light are translated to aluminum/air or aluminum/substrate waveguide light, and the grating acts as a color filter. With both resonances, the bilayer nanowire grating can be a compact-integrated polarizer and color filter.     

Surface Plasmon as a Probe of Local Field Enhancement

New method of experimental determination of local field enhancement at metal nanoparticles is suggested. It uses surface plasmon as a probe. Alternating-sign shift of surface plasmon resonance in copper nanoparticles incorporated in silica matrix has been observed under irradiation by intense femtosecond laser pulse. The red shift of plasmon observed during the action of pump pulse is interpreted as a result of change of dielectric constant of silica matrix due to optical Kerr effect in electric field of pump pulse enhanced in a vicinity of metal nanoparticles. The field enhancement factor is estimated from the value of the observed red shift of plasmon resonance.     

Multiple Surface Plasmon Resonances in Compound Structure with Metallic Nanoparticle and Nanohole Arrays

The optical properties of a compound structure with metallic nanoparticle and nanohole arrays are numerically investigated by the means of finite-difference time domain method. We report on the observation of multi-valleys in the reflection spectra due to the excitation of surface plasmon (SP) resonant modes of the compound structure. Simulation results show that multiple SP resonances consist of surface plasmon polaritons on the gold film, localized surface plasmons on the nanoparticles, and coupling mode between them. These findings are important for applications utilizing multiple surface plasmon resonances.     

Localized Surface Plasmon Resonances of Simple Tunable Plasmonic Nanostructures

Plasmonics - We derive and present systematic relationships between the analytical formulas for calculation of the localized surface plasmon resonances (LSPR) of some plasmonic nanostructures which...     

Giant Infrared Sensitivity of Surface Plasmon Resonance-Based Refractive Index Sensor

Surface plasmons (SPs), the coherent charge density oscillations of the electrons bound to the metal-dielectric interface, are dominating the research field of optics. One of the ubiquitous applications of SPs is in sensing. In the present work, we have theoretically studied a couple of surface plasmon resonance (SPR)-based fiber-coupled ultra-sensitive refractive index sensors working in the infrared (IR) region. Either of the copper (Cu) and aluminum (Al) is used as surface plasmon exciting layers in these sensing probes. On the top of the metal layer, field-enhancing graphene and silicon layers are considered. The probes are characterized in terms of sensitivity and detection accuracy (DA). The sensitivities of Cu- and Al-based optimized probes are obtained respectively to be 23.50 and 24 μm/refractive index unit (RIU). To ensure the probes’ compatibility with bio-samples, an extra bio-recognition layer of graphene has been considered over the silicon layer which resulted into the respective sensitivities of 20 and 19.50 μm/RIU for Cu- and Al-based probes with appreciably good DAs.