Surface Plasmon Resonant THz Wave Transmission on Carbon Nanotube Film

The properties of the terahertz resonant surface plasmons wave on the carbon nanotube film and dielectric interface have been investigated. As a first step towards engineering terahertz SPPs-like surface modes, we present a computer experiment to demonstrate that the carbon nanotube film surface can also be employed to concentrate and guide the terahertz SPPs wave. The carbon nanotube film is modeled in an experimentally realizable geometry. It is shown that a unique electromagnetic surface mode in terahertz region can be supported along the carbon nanotube film/dielectric interface when the free-space broadband terahertz pulse is incident on the carbon nanotube film with subwavelength gratings. Comparing with noble metals, plasmonic nano-structure materials based on carbon nanotube film offer a potentially more versatile approach to engineering tightly confined surface modes in the THz regime.     

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.     

Sensitivity Enhancement of Ag-ITO-TMDCs-Graphene Nanostructure Based on Surface Plasmon Resonance Biosensors

Plasmonics - The novel configuration of surface plasmon resonance (SPR) based on Ag-indium tin oxide (ITO)-transition metal dichalcogenides (TMDCs)-graphene hybrid structures is proposed for highly...     

Surface Plasmon Enhancement of Optical Absorption in Thin-Film Silicon Solar Cells

Strong electromagnetic field enhancement that occurs under conditions of the surface plasmon excitation in metallic nanoparticles deposited on a semiconductor surface is a very efficient and promising tool for increasing the optical absorption within semiconductor solar cells and, hence, their photocurrent response. The enhancement of the optical absorption in thin-film silicon solar cells via the excitation of localized surface plasmons in spherical silver nanoparticles is investigated. Using the effective medium model, the effect of the nanoparticle size and the surface coverage on that enhancement is analyzed. The optimum configuration and the nanoparticle parameters leading to the maximum enhancement in the optical absorption and the photocurrent response in a single p-n junction silicon cell are obtained. The effect of coupling between the silicon layer and the surface plasmon fields on the efficiency of the above enhancement is quantified as well.     

Photoconductivity of Silver Nanoparticle Ensembles on Quartz Glass (SiO2) Supports Assisted by Localized Surface Plasmon Excitations

We have studied the conductivity and photoconductivity in silver nanoparticle ensembles on quartz glass substrates. We observed a significant increase of the photoconductivity if the localized surface plasmon resonance in the metal nanoparticles was excited. A detailed analysis of the temperature dependence of the conductivity as well as dependences of the conductivity and photoconductivity on the amount of deposited metal led to the mechanism of the charge transfer in these structures. We found that the primary role in this mechanism is due to defects in the quartz glass structure which act as traps for electrons.     

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.     

Large Nonlinearity Enhancement of Ag/MEH-PPV Nanocomposite by Surface Plasmon Resonance at 1,550 nm

We experimentally demonstrate a large third-order nonlinear susceptibility for a nanocomposite made of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] doped with silver nanoprisms at 1,550 nm, achieved based on nonlinearity enhancement associated with strong surface plasmon resonance. The nonlinear refractive index reaches −1.37 × 10⁻¹² m²/W, which is three orders of magnitude larger than that of pure poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]. An ultrafast response time of 18.7 ps is reached using fast energy transfer from excited states of organic molecules to silver nanoprisms. A low-power and ultrafast nanocomposite photonic crystal all-optical switching is also realized.     

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,...     

Quantification of the Field Enhancement of Surface Plasmon Under Standing Wave Conditions

Plasmonics - We performed a quantitative study of the field intensity under surface plasmon (SP) using different impinging source changing the beam width for several metallic structures and compare...     

Resonant Mode Analysis of the Nanoscale Surface Plasmon Polariton Waveguide Filter with Rectangle Cavity

The resonant mode characteristics of the nanoscale surface plasmon polaritons (SPP) waveguide filter with rectangle cavity are studied theoretically. By using the finite difference time domain method, both the band-stop- and band-pass-type rectangle SPP filters are analyzed. The results show that the whispering gallery mode (WGM) and the Fabry–Perot (FP) mode can be supported by the rectangle SPP resonator. Furthermore, both traveling-wave mode and standing-wave mode can be realized by the WGM, while only standing-wave mode can be introduced by the FP mode. The traveling-wave mode can only be realized by the square-shaped SPP resonator, and the traveling-wave mode is splitted into two standing-wave modes by transforming the cavity shape from square to rectangle. Also, the effects of the cavity shape, cavity size, and coupling gap size on the transmission spectra of the SPP resonators are analyzed in detail. This simple SPP waveguide filter is very promising for the high-density SPP waveguide integrations.     

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.     

Transmission Surface Plasmon Resonance Signal Enhancement via Growth of Gold Nanoparticles on a Gold Grating Surface

We developed a novel technique for increasing the sensitivity of transmission surface plasmon resonance (T-SPR) signals. T-SPR spectroscopy was performed by irradiating, with white light, a gold grating substrate whose surface was nanostructured by growing gold nanoparticles (AuNPs). AuNPs were grown directly on the substrate surface by alcohol reduction and their growth was observed at various stages by UV–visible spectroscopy and standard Kretschmann-type SPR spectroscopy. For comparison, normal gold film with smooth surface was examined under similar condition. The T-SPR results show a possibility of hybrid excitation of both localized and propagating surface plasmon. Significantly, T-SPR spectra of the gold grating substrate obtained during AuNP growth show stronger and narrower peaks in the range 650–800 nm. The maximum T-SPR excitation was at an incident angle of 35°. A layer-by-layer system of 5,10,15,20-tetrakis (1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate) molecules and sodium copper chlorophyllin molecules was used to verify the enhancement of the developed system. We believe that the AuNPs/Au grating for T-SPR devices will provide enhanced signals for detecting nanometer order materials and for high-sensitive sensor applications.     

Impact of Propagative Surface Plasmon Polaritons on the Electromagnetic Enhancement by Localized Gap Surface Plasmons Between Metallic Nanoparticles and Substrate

Plasmonics - The nanoparticle-on-mirror system as a surface-enhanced Raman scattering substrate is sufficient for single molecule detection and possesses advantages of high reproducibility and ease...     

Resonant Enhancement of Photoluminescence Intensity and Anisotropy of Quantum Dot Monolayers with Self-Assembled Gold Nanorods

Plasmonics - Quantum dot (QD) films are well known as promising materials for photo-detectors and photovoltaic and next generation display devices. In this study, we show, experimentally, how...     

Eigenmode Decomposition of the Near-Field Enhancement in Localized Surface Plasmon Resonances of Metallic Nanoparticles

I present a direct and intuitive eigenmode method that evaluates the near-field enhancement around the surface of metallic nanoparticles of arbitrary shape. The method is based on the boundary integral equation (BIE) in the electrostatic limit. Besides the nanoparticle polarizability and the far-field response, the near-field enhancement around nanoparticles can be also conveniently expressed as an eigenmode sum of resonant terms. Moreover, the spatial configuration of the near-field enhancement depends explicitly on the eigenfunctions of both the BIE integral operator and of its adjoint. It has also established a direct physical meaning of the two types of eigenfunctions. While it is well known that the eigenfunctions of the BIE operator are electric charge modes, it is less known and used that the eigenfunctions of the adjoint represent the electric potential generated by the charge modes. For the enhanced spectroscopies, the present method allows an easy identification of hot spots which are located in the regions with maximum charge densities and/or regions with fast variations of the electric potential generated by the charge modes on the surface. This study also clarifies the similarities and the differences between the far-field and the near-field behavior of plasmonic systems. Finally, the analysis of concrete examples like the nearly touching dimer, the prolate spheroid, and the nanorod illustrate some modalities to improve the near-field enhancement.     

Systematic Evolution of Resonant Coupling Behavior Between Surface Plasmon Polaritons and Multi-waveguide Modes in Metal-Dielectric Multi-layers

Plasmonics - A multi-layer structure consisting of metal and dielectric layers which allows coupling between surface plasmon polaritons and waveguide modes is studied by calculating reflectivity...     

Experimental Demonstration of Spoof Surface Plasmon Based THz Antennas for Huge Electric Field Enhancement

Plasmonics - We experimentally demonstrate the fabrication and optical measurement of a novel terahertz antenna array due to the excitation of spoof surface plasmon modes. With the unit cell...     

Emission Enhancement of Light-Emitting Diode by Localized Surface Plasmon Induced by Ag Inserts in p-GaN and TiO2-Ag Grating

Plasmonics - The structure composed of a TiO2-Ag grating on the surface of p-GaN layer is proposed and investigated. The performance of light-emitting diodes is enhanced by coupling of localized...     

Surface Plasmon Effects Excited by the Dielectric Hole in a Silver-Shell Nanospherical Pair

Using the finite-element method, the surface plasmon effects in a three-dimensional silver-shell nanospherical pair with five different dielectric holes (DHs) that interact with a transverse magnetic mode incident plane wave are investigated. The proposed structure exhibits a red-shifted localized surface plasmon that can be tuned over an extended wavelength range by varying the dielectric constant and the radii in DHs. The increase in the near-field intensity is attributed to a larger effective size of DH that is filled with a higher refractive index medium. The predictive character of these calculations allows one to tailor the shape of the nanoparticle to achieve excitation spectra on demand with a controlled field enhancement.     

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.