This PDF file contains the front matter associated with SPIE Proceedings Volume 7394, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

In this work we perform correlated structural and optical studies of single nanoparticles as well as explore the generality of SMSERS. First, wide-field plasmon resonance microscopy is used to simultaneously determine the LSPR spectra of multiple Ag nanoprisms, whose structure is determined using TEM. Next, the structure-property relationships for well-defined and easily-controlled nanoparticle structures (e.g. monomers, dimers, and trimers) are studied using correlated TEM, LSPR, and SERS measurements of individual SERS nanotags. We present the SER spectrum of reporter molecules on a single nanotag comprised of a Au trimer. It was determined that of 40 individual nanotags, just 19 exhibited SERS. The remaining nanoparticles were established by TEM to be monomers. These results demonstrate that SERS signal is observed from individual nanotags containing a junction or hot spot. Lastly, we explore crystal violet, a triphenyl methane dye that was used in the seminal SMSERS investigations, and re-examine single-molecule sensitivity using the isotopologue approach.

Here we report the design, the fabrication and measurement of a photonic-plasmonic device that is fully compatible with AFM microscopy and surface enhanced Raman spectroscopy. The physical mechanism exploited is the adiabatic compression of Surface Plasmon Polaritons which propagate along a silver nanocone generating a very high electric field at the tip end. A photonic crystal cavity is employed to efficiently couple the external laser radiation with the nanocone. The reported measurements demonstrate the accumulation of the electric field at the tip of the nanocone that allow the detection of a few molecules located near the tip end. The estimated Raman enhancement factor is about 10⁶ with respect to a standard configuration. The present results open a good perspective for the development of an integrated Raman-AFM microscopy able to perform both topography and chemical mapping in label free condition with a spatial resolution comparable to the tip end.

There has been considerable interest in nano-cavity lasers, both from a scientific perspective for investigating fundamental properties of lasers and cavities, and also to produce smaller and better lasers for low-power applications. Light confinement on a wavelength scale has been reported in photonic crystal nano-cavities. Even stronger light confinement can be achieved in metallic cavities which can confine light to volumes with dimensions considerably smaller than the wavelength of light. It was commonly believed, however, that the high losses in metals are prohibitive for laser operation in metallic nano-cavities. Recently we have reported lasing in a metallic nano-cavity filled with an electrically pumped semiconductor. Importantly, the manufacturing approach employed for these devices permits even greater miniaturization of the laser. In particular Metal-Insulator-Metal (MIM) waveguides with dimensions well below the diffraction limit can be fabricated using our techniques. Experimental results from such MIM waveguide lasers will be presented. In theory it is shown that it is possible to reduce the semiconductor gain medium dimensions of these MIM waveguide devices down to a few tens of nanometers in size. Finally, latest results for the fabrication of MIM type waveguide devices will also be examined.

Superoscillations are regions of band-limited waves where the local wavenumber, defined as the local phase gradient, exceeds the global maximum wavenumber in the Fourier spectrum. In random functions, defined as superpositions of plane waves with random complex amplitudes and directions, considerable regions are naturally superoscillatory (M. R. Dennis, et al., Opt. Lett. 33, 2976-2978, 2008; M. V. Berry and M. R. Dennis, J. Phys. A: Math. Theor. 42, 022003, 2009). We discuss this result by deriving the joint probability density function for intensity and phase gradient of isotropic complex random wave in any dimension, with specific reference to the one-dimensional case.

We report the first experimental demonstration of far-field lensing using a plasmonic slit array. We implement a planar nano-slit lens using a combination of thin film deposition and focused ion beam milling. Our lens structures consist of optically thick gold films with micron-size arrays of closely-spaced, nanoscale slits of varying widths milled using a focused ion beam. We demonstrate experimentally that it acts as a far-field cylindrical lens for light at optical frequencies. We show excellent agreement between the full electromagnetic field simulations of the design, which include both evanescent and propagating modes, and the far-field, diffraction-limited confocal measurements on manufactured structures. The flexibility offered by these slit-based planar lenses allows for the design of microlenses that compensate for oblique illumination in integrated opto-electronic systems, such as complementary metal-oxide semiconductor (CMOS) image sensors.

Metamaterial and plasmonic composites have led to the realization that new possibilities abound for creating materials displaying functional electromagnetic properties not realized by nature. Recently, we have extended these ideas by combining metamaterial elements - specifically, split ring resonators - with MEMS technology. This has enabled the creation of non-planar flexible composites and micromechanically active structures where the orientation of the electromagnetically resonant elements can be precisely controlled with respect to the incident field. Such adaptive structures are the starting point for the development of a host of new functional electromagnetic devices which take advantage of designed and tunable anisotropy.

We theoretically and experimentally investigate the optical properties of a subwavelength hole in a thin metallic film. The microscopic origin of the hole plasmon resonance is a collective state formed by propagating thin film surface plasmons of wavelengths equal to integer fractions of the hole diameter. We show that the plasmon resonance depend strongly on the polarization of the incident light. We also, using time-domain terahertz spectroscopy, demonstrate the first experimental observation of the optical coupling between antibonding film plasmon modes and perpendicularly polarized light to the film surface.

The phenomenon of anomalous transmission through subwavelength aperture arrays in metallic films (plasmonic lattices) is thought to be mediated by surface plasmon polaritons (SPP) on the film surfaces. Using terahertz time-domain spectroscopy we systematically studied the anomalous transmission spectrum through plasmonic lattices as a function of the incidence angle, θ of the impinging beam. We observed splitting of the various transmission resonances into two resonance branches when θ deviates from normal incidence that depends on the polarization direction of the beam respect to the plane of incidence and θ. We show that the transmission resonance splitting is not related to dispersion relation of different SPP branches, but rather is associated to the interference properties of the SPP waves on the metal surface. The dependence of the split resonant frequencies vs. θ is fit with a theoretical formula that takes into account the effective dielectric function of the plasmonic lattice vs. θ, which emphasizes the important role of the Fanotype anti-resonances in the transmission spectrum. Finally, we introduced a simple way for making an efficient notch filter with high Q factor exploiting the splitting of transmission resonance under rotation.

Here, for the first time we predict a giant surface plasmon-induced drag effect (SPIDEr), which exists under conditions of the extreme nanoplasmonic confinement. Under realistic conditions, in nanowires, this giant SPIDEr generates rectified THz potential differences up to 10 V and extremely strong electric fields up to ~ 10⁵ ~ 10⁶ V/cm. The SPIDEr is an ultrafast effect whose bandwidth for nanometric wires is ~ 20 THz. The giant SPIDEr opens up a new field of ultraintense THz nanooptics with wide potential applications in nanotechnology and nanoscience, including microelectronics, nanoplasmonics, and biomedicine.

Gold/vanadium dioxide nanoparticles (NPs) were produced with the intention of creating a hybrid NP retaining the characteristic semiconductor-metal phase transition of VO₂ and the plasmonic properties of gold. The fabrication procedure for arrays of the hybrid structure is presented with optical characterization and analysis of the plasmonic structure. The high-temperature anneal required to insure the stoichiometry of the VO₂ leads to dewetting of the Au from the underlying VO₂ layer, and to dramatic reshaping of the gold NP. Surface enhanced Raman spectroscopy verifies the retention of the VO2 crystalline structure and phase transition; white light extinction measurements exhibit the polarization sensitive plasmonic resonance peaks that characterize the electronic signature of the phase transition. Together these techniques show that the composite system experiences no significant intermingling between the two materials during processing. Furthermore, the controllable nature of the extent of dewetting, via aspect ratio of the pre-annealed particle, suggests that the hybrid system will give insight into interface interactions between the optical and structural properties of the constituents. A second method is suggested to circumvent the annealing effect. The conclusions of our investigation suggest applications as both a thermally or optically tunable plasmonic structure.

Temporal changes in signal intensity of Surface Enhanced Raman Scattering (SERS) upon laser excitation is an interesting phenomenon in plasmonics. In-depth understanding of the phenomena is highly important especially when developing a SERS sensor based on the intensity variation of particular Raman peak/band. One of the main challenges in such a technique is the intensity reduction at a given location upon consecutive measurements. Previously, signal loss in SERS measurement was attributed to the electric-field induced roughness relaxations in the SERS active surface. In such cases, as the surface is smoothened out, signals are completely lost. In our observation, the reduction in the spectral intensity is irreversible but never completely lost and a major part of it can be attributed to the plasmon induced heating effect. Here, we experimentally demonstrate this effect by studying the SERS signal from four different Raman active molecules adsorbed onto substrates that contain uniform nano-roughened bi-metallic silver/gold coating. Possible mechanism that leads to irreversible signal loss is explained. Moreover, solutions for minimising such plasmonic heating when developing a biosensor are also discussed.

High harmonic generation is a well-established optical method to produce coherent short-wavelength light in the ultraviolet and soft-X ray range. This nonlinear conversion process requires ultrashort pulse lasers of strong intensity exceeding the threshold of 10¹³ Wcm^-2 to ionize noble gas atoms. Chirped pulse amplification (CPA) is popularly used to increase the intensity power of a femtosecond laser produced from an oscillator. However, CPA requires long cavities for multi-staged power amplification, restricting its practical uses due to hardware bulkiness and fragility. Recently, we successfully exploited the phenomenon of localized surface plasmon resonance for high harmonic generation, which enables replacing CPA with a compact metallic nanostructure. Surface plasmon resonance induced in a well-designed nanostructure allows for intensity enhancement of the incident laser field more than 20 dB. For experimental validation, a 2D array of gold bowtie nanostructure was fabricated on a sapphire substrate by the focused-ion-beam process. By injection of argon and xenon gas atoms onto the bowtie nanostructure, high harmonics up to 21^st order were produced while the incident laser intensity remains at only 10¹¹ Wcm^-2. In conclusion, the approach of exploiting surface plasmons resonance offers an important advantage of hardware compactness in high harmonic generation.

When a metallic nanostructure is illuminated by ultrashort light pulses, the excitation of surface plasmons is observed along with subsequent strong enhancement of the electric field in the vicinity of the nanostructure. This localized surface plasmonic resonance is exploited to generate coherent extreme ultraviolet light and soft-X ray by interacting noble gas atoms with femtosecond laser pulses. The resulting field enhancement is much affected by the 3-D shape of the used nanostructure, so various nanostructure shapes are examined through finite-difference time-domain analysis to predict their performance in high harmonic generation.

In this work, we present an investigation of the nonlinear optical properties of nanoshells of different size in solutions and deposited on glass substrates using a single beam z-scan method at a wavelength of 806 nm with laser duration of 170 fs. Structural properties of gold nanoshells of about 150 and 220 nm, prepared in water, are characterized by AFM and TEM microscopy. It is found that, in general, they behave as saturable absorbers. The level of saturation depends on the relative overlap between the plasmon resonance of nanoshells and the laser excitation wavelengths. The nonlinear absorption coefficient, obtained by fitting the experimental results, is of the order of -10^-11 cmW^-1.

Metal nanowires with proper length give strong antenna-like plasmonic resonances in the infrared. Their resonance spectrum is a sensitive measure not only of their geometry but also of their conductivity as we will show for lead nanoantennae here.

There is renewed interest in using rectennas (consisting of an antenna coupled to a rectifying diode) for energy conversion applications. Progress in nanofabrication has enabled nanoscale devices to be fabricated, such that "nanoantennas" exist that resonate at visible/near-infrared (vis/nir) wavelengths, and ultrafast "nanodiodes" exist that can rectify vis/nir frequencies (above 10¹⁴ Hz). Photon energies are so high at these frequencies that existing theories of diode responsivity may not apply, justifying new simulations and experiments. We present modeling and experiments of nanoantenna-coupled nanodiodes, such as metal-insulator-metal structures, and discuss how our findings influence models of energy conversion in these structures. We simulate and measure the properties of potential nanorectennas such as gold nanowires on ultrathin insulators.

Individual small gold structures of different sizes and shapes are fabricated on planar substrates for subsequent characterization of their optical properties. In the process, a combination of thin-film metallization, electron beam lithography and ion milling is employed, where electron beam structured hydrogen silsesquioxane is used as an etch mask for the underlying gold layer. Gold cones, vertical rods, cups and flat disks can be prepared with a typical height of about 100 nm. Their optical properties are investigated by confocal optical microscopy using a parabolic mirror for both laser focusing and signal collection. As an example, the photoluminescence signal collected from an array of gold cones is shown.

Nanostructured metal-ZnO systems provide an ideal workbench for studying the dynamics of exciton-plasmon coupling. In order to characterize the interactions, we grew tri-layer structures comprising thin films of ZnO, variable-thickness spacer layers of MgO, and thin films of Ag or Au. Analysis of the photoluminescence of these structures as a function of increasing MgO thickness confirms the existence of surface plasmon polariton-exciton coupling through Purcell enhancement of the excitonic emission for MgO films thinner than 30 nm, and through emission at the SPP resonance for MgO films thicker than 30 nm. Further, we demonstrate the enhancement of the ZnO impurity photoluminescence through dipole-dipole scattering with Ag and Au LSPs. Preliminary degenerate band-edge pump-probe measurements confirm the conclusions developed from photoluminescence measurements. In order to disentangle and further quantify the interactions seen in these systems, we are lithographically patterning metal nanoparticle arrays and metal hole arrays on ZnO quantum wells and beginning to perform white-light pump-probe spectroscopy to fully characterize the dynamics of energy transfer within these systems.

The spin-Hall effect - the influence of the intrinsic spin on the electron trajectory, which produces transverse deflection of the electrons, is a central tenet in the field of spintronics. Apparently, the handedness of the light's polarization (optical spin up/down) may provide an additional degree of freedom in nanoscale photonics. The direct observation of optical spin-Hall effect that appears when a wave carrying spin angular momentum interacts with plasmonic nanostructures is presented. The measurements verify the unified geometric phase, demonstrated by the observed spin-dependent deflection of the surface waves as well as spin-dependent enhanced transmission through coaxial nanoapertures even in rotationally symmetric structures. Moreover, spin-orbit interaction is demonstrated by use of inhomogeneous and anisotropic subwavelength dielectric structures. The observed effects inspire one to investigate other spin-based plasmonic effects and to propose a new generation of optical elements for nanophotonic applications.

We demonstrate enhanced diffractive coupling resulting in sharpened extinction resonances in periodic arrays of metal nanoparticles embedded effectively below the substrate surface. Strongly enhanced near fields with large spatial overlap with the substrate material are shown to be associated with these extinction features. In particle arrays fabricated on substrates there is a phase velocity mismatch between light propagating above and below the substrate surface, which hinders diffractive coupling and access to such narrow resonances. In contrast, the embedding of the particle arrays beneath the substrate surface, achieved via an etching procedure, offers a more homogeneous dielectric background which improves the diffractive coupling, resulting in the sharp features associated with strong near field enhancements.

We theoretically investigate the properties of absorption switches for metal-dielectric-metal (MDM) plasmonic waveguides. We show that a MDM waveguide directly coupled to a cavity filled with an active material with tunable absorption coefficient can act as an absorption switch, in which the on/off states correspond to the absence/presence of optical pumping. We also show that a MDM plasmonic waveguide side-coupled to a cavity filled with an active material can operate as an absorption switch, in which the on/off states correspond to the presence/absence of pumping. For a specific modulation depth, the side-coupled-cavity switch results in more compact designs compared to the directcoupled- cavity switch. Variations in the imaginary part of the refractive index of the material filling the cavity of Δκ=0.01 (Δκ=0.15) result in ~60% (~99%) modulation depth. The properties of both switches can be accurately described using transmission line theory.

The electromagnetic (EM) eigenstates of a thin, long circular cylinder, for which a very good approximate closed form expression wasderived earlier, are used to set up a numerical computation of the EM eigenstates of a cluster of parallel cylinders. Detailed results are presented for a pair of identical cylinders, as well as for a cluster of three identical cylinders, where the cylinder axes are situated at the vertices of an equilateral triangle. The aim is to find an eigenstate that has an electric dipole moment and a magnetic dipole moment of comparable magnitudes. By operating the system near such an isolated resonance, it should be possible to tweak the macroscopic response so as to have both the macroscopic electric permittivity ε_e and the macroscopic magnetic permeability μ_e attain desirable values, e.g., values that are almost real and negative. It is argued that a three-cylinder cluster is a good configuration for achieving this goal, but a two-cylinder cluster is not.

The localized surface plasmon resonance (LSPR) of a nanoplasmonic particle is often considered to occur at a single resonant wavelength. However, the physical measures of plasmon resonance, namely the far-field measures of scattering, absorption, and extinction, and the near-field measures of surface-average or maximum electric field intensity, depend differently on the particle polarizability, and hence may be maximized at different wavelengths. We show using analytic Mie theory that the differences in peak wavelength between the near- and far-fields can reach over 200 nm for nanoparticle sizes commonly used in spectroscopy applications. Using finite element analysis, we also consider the effect of varying particle shape to spheroidal geometries, and consider polarization dependence. Using the quasi-static and extended quasi-static approximation, we show that the differences between the near- and far- field measures of plasmon resonance can be largely explained by radiation damping effects. We suggest that accounting for these differences is relevant both for optimizing device design, and for improving fundamental understanding of surface-enhanced mechanisms such as surface-enhanced Raman spectroscopy (SERS).

The design of structures capable of producing strong electric near-fields has become an active area of plasmonics research with applications including sensor technology, surface enhanced Raman scattering and plasmon solar cells. The purposeful design of plasmonic systems is complicated by the problem of finding analytical solutions to Maxwell's equations. Recently we developed a theory, based on a simplification of the boundary element method (BEM), for modeling the interaction between plasmonic nanoparticles mediated by their evanescent electric fields. The theory makes extensive use of "electrostatic" resonances in which the nanoparticle system is taken to be much smaller than the wavelength of the exciting radiation. The key result is an expression describing the "electrostatic" coupling between arbitrarily-shaped particle pairs, expressed in terms of their resonant eigenmodes. Simple analyses of two and three particle systems predict the formation of "dark modes" in which the dipole scattering cross section becomes small but the evanescent electric fields remain large.

Optical properties of a planar array of composite Au/Co/Au magnetic plasmonic nanosandwiches of 60 and 110 nm in diameter are studied using linear absorption and optical second harmonic generation (SHG) technique. Linear absorption spectrum reveals a peak centered at about 2.1 eV, which is associated with the excitation of localized surface plasmon in Au/Co/Au nanosandwiches. The nonlinear-optical experiments are performed using the fundamental radiation of YAG: Nd3+ laser at 1064 nm, so that the SHG radiation corresponds to the resonant plasmon line. It is shown that in spite of spatial inhomogeneity of such an ensemble, the SHG response in the nanosandwiches of the diameter 110 nm is presumably polarized and specular, i.e. substantially coherent. At the same time, for nanosandwiches with the diameter of 60 nm the SHG signal is observed in the form of the hyper-Rayleigh scattering. Plasmon-assisted effects in nonlinear-optical response of nanosandwiches reveal themselves by different relative amplitude and phase of odd in magnetization component of the SHG field as compared with those in plasmon-free continuous trilayer structure.

In the present work, we report optical and nonlinear optical properties of Ag - Polyvinyl alcohol polymer films prepared through a chemical method. Optical absorption measurements show the surface plasmon resonance (SPR) around 410 nm. The SPR intensity increases with annealing temperature. Open aperture z-scan measurements done using 100 femtosecond laser pulses at 400 nm show an intensity dependent nonlinear light transmission behavior.

Enhanced transmission has been associated with surface wave excitation and aperture arrangement on a metallic film. Aperture resonances, however, have been demonstrated to exist without an order in the arrangement of apertures, with properties dependent on geometry and optical properties of the aperture filling. These resonances are accompanied by wavelength-dependent phase shifts in the transmitted fields offering the potential for manipulation of wavefields. Here, we present Finite Element Method simulations investigating light passing through periodic arrays of nanometric spatially varying near-resonant slits perforated in a metallic film. We show that a tailored phase modulation can be introduced into an incident optical wavefield by varying aperture sizes around the resonant dimensions for a particular design wavelength, permitting control of wavefields which can be employed for beam deflection, beam focusing or for producing a wavelength-specific spatial field change.

We observe critical coupling to surface phonon-polaritons in silicon carbide by attenuated total reflection of mid-infrared radiation. Reflectance measurements demonstrate critical coupling by a double-scan of wavelength and incidence angle. Critical coupling occurs when prism coupling loss is equal to losses in silicon carbide and the substrate, resulting in maximal electric field enhancement.

Ag_1-xCu_xI (x= 0.10, 0.20, and 0.50) thin films with thicknesses upto15 nm produced by thermal co-evaporation onto glass substrates were systematically iodized and carefully characterized. Optical absorption spectra of uniodized Ag-Cu films show intense surface plasmon resonance (SPR) features with maxima at 430, 445 and 445 nm for the films of thickness 5, 10 and 15 nm respectively and a gradual transition to zincblende AgI exciton with optical signatures at 425 nm. Delayed evolution and inhomogeneous broadening of the exciton absorption at 425 nm of the spatially confined γ- AgI nanoparticles were clearly seen by the development of Z_1,2 and Z₃ exciton peaks iodization kinetics being controlled by the as-quenched Ag-Cu clusters. Cu addition not only restricts the particle size, but also favors the island type growth mode. PL observed at 428 nm shows a thickness and Cu-composition dependent intensity suggesting the involvement of Frenkel defects in non-radiative recombination.

In this work, we use glancing angle deposition (GLAD) to fabricate a silver nanorod array. The average tilt angle and diameter of the silver nanorod are 65° ± 5 and 323 nm, respectively. When the array is illuminated by normal incident light, oscillating electric field parallel to the rod and perpendicular to the rod would induce the transverse and longitudinal plasmon resonant modes. As the longitudinal plasmon mode occurs, the absorption of the array with thickness 323nm is enhanced and the TM mode transmittance is reduced to be 0.3 percentages. The transmitted ellipsometric parameters are measured and the phase difference between TE mode and TM mode transmission coefficients is detected. The absolute transmission coefficient is measured by walk-off interferometer. Compared with the relative phase, the phase of TM mode transmission coefficient becomes a negative value. It is proposed here that a wave propagates through the "effective thin film" and acts like a backward wave in the film.

The glancing angle deposition (GLAD) technique is applied to fabricate a three-layered dielectric-metal-dielectric anisotropic thin film. The silver nanorod array is between two SiO₂ nanorod arrays (NRA). The three-layered thin film is arranged in the Kretschmann configuration and measured the reflectance of the system. The polarization conversion reflectance is measured from this system as the plane of incidence is not coincident with the deposition plane. From the angular spectra of reflectance for R_PP, R_SS, R_SP and R_PS (R_ij, i denotes the polarization of the incident beam and j denotes the polarization of the reflected light) measured at angles larger than critical angle, the absorption for s-polarization and p-polarization incident light can be calculated. The resonant peaks varied with the orientation of the deposition plane are also measured. The configuration combines polarization conversion, transverse surface plasmon resonance and longitudinal surface plasmon resonance of the rods. Those resonances are associated with the relationship between the rod directions and the oscillating electric field vector. The variations of the absorption peaks affected by those resonant modes are discussed in this work.

Noble metal nanoparticles (MNPs) are widely used for fabrication of metal-dielectric plasmonic nanostructures with optical properties attractive for applications. The MNPs embedded in a glass matrix are known to exhibit an intense color related to the resonance oscillation of the free conduction electrons known as surface plasmon resonance (SPR). Silver nanoparticles with diameter about 2 nm are shown to be formed in the subsurface layer of photothermorefractive (PTR) glasses after electron beam irradiation with subsequent heat treatment. The type of MNPs depends on the composition of the PTR glass. The size distribution and MNP concentration depend on irradiation dozes and heat treatment temperatures. The report presents the technology of silver NP fabrication, experimental optical absorption spectra, low frequency Raman scattering, and TEM images used for determination of the MNP size distribution, and simulation of optical extinction spectra using generalized Mie model of light scattering.

In this work we demonstrate the use of holographic lithography for generation of large area plasmonic periodic structures. Submicrometric array of holes, with different periods and thickness, were recorded in gold films, in areas of about 1 cm², with homogeneity similar to that of samples recorded by Focused Ion Beam. In order to check the plasmonic properties, we measured the transmission spectra of the samples. The spectra exhibit the typical surface plasmon resonances (SPR) in the infrared whose position and width present the expected behavior with the period of the array and film thickness. The shift of the peak position with the permittivity of the surrounding medium demonstrates the feasebility of the sample as large area sensors.

Previous observations on arrays of single nanoparticles (NPs) have shown that particle separation and grating constant determine the peak extinction wavelength of the local surface plasmon resonance (LSPR). Recently, it has been predicted that the LSPR peak extinction wavelength in arrays of nanodimers (NDs) exhibit enhanced sensitivity to changes in the local dielectric function compared to single NPs. In order to test this prediction, arrays of NPs, NDs and heterodimers comprising three different NP sizes were fabricated by electron-beam lithography with various grating constants, particle diameters, and interparticle separations. Another set of arrays were also fabricated and coated with approximately 60-nm of vanadium dioxide, which undergoes an insulator to metal phase transition at a critical temperature near 68.C. By tuning the temperature of the samples through the strong-correlation region around the critical temperature, we varied the effective dielectric constant surrounding the NP arrays over a significant range. Linear extinction measurements on the arrays were made at temperatures above and below the critical temperature, with linear polarizers placed in the incident beam in order to distinguish between LSPR modes. Measurements show a clear dependence of LSPR sensitivity to interparticle separation as well as the dielectric function of the surrounding medium. Finally, finite-difference time-domain (FDTD) simulations were carried out for comparison with the experimental results.

Surface plasmon modes can be considered as the analogous to plane waves for homogeneous media. The extension to partially coherent surface plasmon beams is obtained by means of the incoherent superposition of the interference between surface plasmon modes whose profile is controlled associating a probability density function to the structural parameters implicit in their representation. We show computational simulations for cosine, Bessel, gaussian and dark hollow surface plasmon beams.

Silver nanoparticles in sol-gel silica films have been synthesized by heat treatment in air atmosphere. We find that the surface plasmon resonance exhibits a principal peak at 534 nm, longer wavelength than that corresponding to the spherical silver nanoparticles in silica (400 nm). The anisotropy in the geometry of the metallic nanoparticles explains this noticeably red shift of the silver nanoparticles. The effect of solvents (ethanol, cyclohexane and toluene) and ligand (pyridine) on the optical properties of these nanoparticles are measured by UV-vis spectroscopy. The position of the surface plasmon resonance varies from 534 nm up to 573 nm depending on the refractive index or the concentration of the solvents. On the contrary, the surface plasmon resonance is gradually shifted to the blue from 534 nm up to 462 nm when the films were immersed in pyridine due to complexing on the surface of silver nanoparticles. These results show highest sensitivity of the surface plasmon to variations in the local environment of the nanoparticles and they suggest that the films can be used as colorimetric sensors.

Efficiently coupling far field light into a nano structure is a challenge. This limits the utility of many of the nanophotonics devices that have been developed recently, such as waveguides carrying surface plasmon polariton modes with subwavelength confinement and long propagation length. End fire coupling is an option but requires careful alignment and may not be suitable for exciting densely packed arrays of waveguides. This paper investigates the use of a nanoscale bowtie aperture as an antenna for directly coupling far field light into a nanoscale plasmonic waveguide. The paper shows that when the aperture is designed to be resonant the coupling coefficient can be as high as 600% relevant to the energy incident on the open area of the aperture.

Extraordinary optical transmission through nanoholes has recently taken much interest for its promise to a wide range of applications. Enhancement of non-linear optical phenomena and the development of sensitive biosensors are among the leading ones. As a result of recent studies on the subject, it is now widely accepted that either the non-trivial interaction of the localized and extended surface plasmons or only the localized surface plasmons (for direct transmissions) are responsible from the extra-ordinary light transmission effect. On the other hand, there is little conceptual understanding for controlling the localized surface plasmonic behavior of the individual apertures and their coupling to the extended surface plasmons. In this letter, an intuitive and straightforward picture of the extra-ordinary light transmission phenomena is developed using basic antenna principles for the elementary plasmonic excitations and hybridization of these plasmonic excitations in complex nano-apertures. As an example, the model is successfully applied to explain the experimentally observed plasmonic response of the complex rectangular coaxial apertures. Experimentally measured red-shifting of the plasmonic resonances of the rectangular coaxial-apertures with respect to those of the simple rectangular aperture arrays are successfully described and the asymmetric nature of the plasmonic resonances are explained in relation to strong shape anisotropies. Further enhancement of the extra-ordinary light transmission is also predicted by the model and experimentally demonstrated by using rectangular coaxial aperture arrays as a result of significantly larger net dipole moment in the apertures. Model is also verified by rigorous 3D-FDTD calculations.

In this paper we present the effect of gold, silver and oxide thicknesses on the sensitivity of Surface Plasmon Resonance (SPR). SPR sensor with enhanced sensitivities can be realized based on gold/silver films. Surface Plasmons (SP) are electromagnetic waves that transmit along the interference between a metal and a dielectric film, and the electromagnetic wave of the surface plasmons is coupled to oscillations of free electrons in the metal. SPR has attracted interest in many applications such as solar cells, chemical and biological sensing. The potential sensor application by using gold/silver nanocrystal enhanced SPR phenomenon. Sensitivity is a significant parameter to assess the sensor's performance. Essentially, sensitivity is determined by the force of light and matter interaction.