This PDF file contains the front matter associated with SPIE Proceedings Volume 8096, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Visualization of terahertz (THz) plasmons with local probes allows studying ultra-fast plasmonic phenomena in the time domain. We demonstrate that the integrated sub-wavelength aperture near-field probe can be used to map THz surface plasmon waves in space and time with high resolution. Using experimental near-field observations of plasmon waves formed on a metallic surface by tightly focused THz pulses and of standing plasmon waves in THz antennas, we show that this probe detects the spatial derivative of the electric field rather than the plasmon field itself. The understanding of the coupling mechanism provides a framework for interpretation of near-field images.

We report on strong coupling between surface plasmon polaritons and Rhodamine 6G molecules at room temperature. As a reference to compare with, we first determine the dispersion curve of (uncoupled) surface plasmon polaritons on a 50 nm thick film of silver. Consequently, we determine the dispersion curve of surface plasmon polaritons strongly coupled to Rhodamine 6G molecules, which exhibits vacuum Rabi splitting. Furthermore, we present spontaneous emission spectra of Rhodamine 6G on silver, which are shown to change with detector angle due to surface plasmon polariton generation by Rhodamine 6G molecules.

Using metal nanostructures to concentrate optical-frequency electric fields has garnered significant interest in the literature. For example, by combining an organic dye with a nanorod whose plasmon resonance frequency overalps the fluorescence maximum of the dye, a significant enhancement in the fluorescence quantum yield can be observed. The prevalent theory for describing such an enhancement is kinetic and ascribed to an increase in the intrinsic rate of fluorescence, while the rate of non-radiative decay remains constant. Analysis of the literature will reveal that systems exhibiting fluorescence enhancement also show an alteration of the Stokes shift. The traditional kinetic description of plasmon-enhanced fluorescence cannot explain the origin of this shift. Using the well-known theory developed by Onsager and Debye and applied to solvochromism, it will be shown that it is possible to model plasmon-enhanced fluorescence not as an increase in the intrinsic rate of fluorescence, but by a perturbation of the equilibrium, photoexcited dipole moment of an emitter coupled to a gold nanorod. This theory is different from the well-known Gersten-Nitzan model and offers an explanation of the altered Stokes shift in plasmon-enhanced fluorescence systems.

Plasmon lasers are a new class of coherent optical amplifiers that generate and sustain light well below its diffraction limit [1-4]. Their intense, coherent and confined optical fields can enhance significantly light-matter interactions and bring fundamentally new capabilities to bio-sensing, data storage, photolithography and optical communications [5-11]. However, metallic plasmon laser cavities generally exhibit both high metal and radiation losses, limiting the operation of plasmon lasers to cryogenic temperatures, where sufficient gain can be attained. Here, we present room temperature semiconductor sub-diffraction limited laser by adopting total internal reflection of surface plasmons to mitigate the radiation loss, while utilizing hybrid semiconductor-insulator-metal nano-squares for strong confinement with low metal loss. High cavity quality factors, approaching 100, along with strong λ/20 mode confinement lead to enhancements of spontaneous emission rate by up to 18 times. By controlling the structural geometry we reduce the number of cavity modes to achieve single mode lasing.

Properties of split-ring metamaterials are governed by inter-element interactions. These interactions lead to slow eigenmodes of coupling, which, due to their short wavelengths, are ideal candidates for the design of near-field manipulating devices. In this paper we explore the electric and magnetic coupling mechanisms in nano-U and nano-SRR dimers comprising of two identical nano-resonators arranged axially and twisted relative to each other by an arbitrary angle. We study theoretically the couplings in a periodic chain of nano-dimers for the frequencies from 100 to 300 THz. In our analytical model, the electric and magnetic couplings can be expressed through the self and mutual terms for the magnetic and electric field energy. In addition, we incorporate the effect of kinetic inductance due to the inertia of the electrons (noticeable as element dimensions approach 100nm or smaller). The resulting dependence of the electric, magnetic and the total coupling constants on the twist angle within the dimer obtained analytically is shown to agree with numerical simulations (CST Microwave Studio). Our approach should enable an effective design of metamaterial structures with desired properties and would be a useful tool in developing THz range manipulating devices based on propagation of slow waves by virtue of coupling.

Ultrafast all optical magnetization switching in GdFeCo layers on the basis of Inverse Faraday Effect (IFE) was demonstrated recently and suggested as a possible path toward next generation magnetic data storage medium with much faster writing time. However, to date, the demonstrations of ultrafast all-optical magnetization switching were performed with powerful femtosecond lasers, hardly useful for practical applications in data storage and data processing. Here we show that utilization of IFE enhancement in plasmonic nanostructures enables fast all-optical magnetization switching with smaller/cheaper laser sources with longer pulse durations. Our modeling results predict significant enhancement of IFE around all major types of plasmonic nanostructures for a circularly polarized incident light. Unlike the IFE in uniform bulk materials, nonzero value of IFE is predicted in plasmonic nanostructures even with a linearly polarized excitation. Experimentally, all-optical magnetization switching at 20 times lower laser fluence and roughly 100 times lower value of laser fluence/pulse duration ratio is demonstrated in plasmonic samples to verify the model predictions. The path to achieve higher levels of enhancement experimentally is discussed.

High-harmonic generation to produce ultrashort EUV pulses by frequency-upconversion of near-infrared (NIR) pulses requires strong laser intensities. Here we describe a 3-dimensional metallic waveguide that enables plasmonic generation of ultrashort EUV pulses through field enhancement by means of surface-plasmon polaritons. Details on the design and fabrication of the plasmonic waveguide on the tip of a cantilever nanostructure are explained along with discussions on experimental data.

With electrons laser-emitted from a nanoscale tungsten tip by few-cycle Titanium:sapphire oscillator pulses we demonstrate that we have reached the attosecond science regime, meaning that the electronic motion is controlled by the optical electric field of the laser pulses. We observe coherent elastic re-scattering at the parent tip as well as interference of the electronic wavefunction if it is emitted in two emission windows spaced by one optical period. Controlled by the carrier-envelope phase of the laser pulses, we can continuously tune between a single and two emission windows in time. All this is facilitated by field enhancement taking place at the tip's apex. From our results we obtain a field enhancement factor of 3...6, depending on experimental conditions and on experimental signatures.

Arrays of "nanorectennas" consist of diode-coupled nanoantennas with plasmonic resonances in the visible/near-infrared (vis/nir) regime, and are expected to convert vis/nir radiative power into useful direct current. We study plasmonic resonances in large format (~ 1 mm² area) arrays, consisting of electron beam-patterned horizontal (e.g., parallel to the substrate) Ag lines patterned on ultrathin (< 20 nm) tunneling barriers (NiO, NbO_x, and other oxides). Our e-beam fabrication technique is scalable to large dimensions, and allows us to easily probe different antenna dimensions. These tunneling barriers, located on a metallic ground plane, rectify the alternating current generated in the nanoantenna at resonance. We measure the plasmonic resonances in these nanoantennas, and find good agreement with modeling, which also predicts that the electric field driving the electrons into the ground plane (and therefore the rectification efficiency) is considerably enhanced at resonance. Various metal-insulator-metal tunneling diodes, incorporating the afore-mentioned barrier layers and different metals for the ground plane, are experimentally characterized and compared to our conduction model. We observe ~ 1 mV signals from NiO-based nanorectenna arrays illuminated by 532 nm and 1064 nm laser pulses, and discuss the origin of these signals.

Silver nanoparticles dispersed on the surface of an inverted GaN LED were found to plasmonically enhance the nearbandedge emission. The resonant surface plasmon coupling led to a significant enhancement in the exciton decay rate and the ensemble of nanoparticles provided a mechanism to scatter the coupled energy as free space radiation. The inverted LED structure employed a tunnel junction to avoid the standard thick p+ GaN current spreading contact layer. In contrast to a standard design, the top contact was a thin n++ AlGaN layer, which brought the quantum well into the fringing field of the silver nanoparticles. This proximity allowed the excitons induced within the quantum well to couple to the surface plasmons, which in turn led to the enhanced band edge emission from the LED.

We explore new types of plasmonic nanoantennas hybridized with semiconductor and metal oxide active materials to achieve controllable plasmonic switches. Theoretically, the response of the active material is tuned through the free carrier density, and the optical response of a rectangular dimer antenna with a photoconductive gap loading is simulated using a COMSOL finite element numerical model. We describe the experimental realization of plasmonic antenna hybrids using an indium tin oxide (ITO) active medium.

We present calculations on the implementation of attosecond nanoplasmonic streaking (APS) spectroscopy on isolated nanoparticles. APS spectroscopy might enable a remote measurement of plasmonic field oscillations in the optical regime with sub-cycle temporal resolution, where plasmons are excited by a few-cycle near-infrared (NIR) driving field and the associated near-fields are mapped by the energy of photoemitted electrons using a synchronized, time-delayed attosecond extreme ultraviolet (XUV) pulse. We discuss the influence of the near-field spatial distribution and electron kinetic energy on the streaking process. By numerical simulations we show the feasibility of APS spectroscopy using Au nanospheres with 10 nm and 100 nm diameter. We show that the near-elds around the nanoparticles can be spatiotemporally reconstructed and may give detailed insight into the build-up and decay of collective electron motion.

A unified theory of plasmon-assisted resonance energy transfer (RET) between molecules near a metal nanostructure is developed that maintains energy balance between transfer, dissipation, and radiation. It is shown that in a wide range of parameters, including in the near field, RET is dominated by plasmon-enhanced radiative transfer (PERT) rather than by a nonradiative transfer mechanism. The numerical calculations performed for molecules near the Ag nanoparticle indicate that RET magnitude is highly sensitive to molecules' positions.

Theory of energy transfer interactions between a pair of two level molecules in the molecular nanojunction including surface plasmon (SP) dressed interaction of plasmonic nanostructure, replicating metallic leads is presented. Results on the modification of bare dipolar interaction, known to be responsible for molecular energy transfer processes, in the proximity of metallic nanosystem are presented. Specifically, the manuscript includes theoretical investigation of nanosphere (NSP) monomer, nanoshell (NSH) monomer, and coupled nanosphere pair (dimer) based nanosystems. Closed form analytical expressions for NSP and NSH structures tailored for molecular nanojunction geometry are derived in the theoretical framework of multipole spectral expansion (MSE) method, which is straightforwardly extendible to dimers and multimers. The role of size and dielectric environment on energy transfer is investigated and interpreted. Theory predicts that the monomer and dimer both enhance the dipolar interaction, yet, dimer geometry is favorable due to its spectral tuning potential originated from plasmon hybridization and true resemblance with typical molecular nanojunctions.

In this work we study how plasmon modes of gold dimers are affected by a molecular bridge connecting both particles. Different models for the linker are considered to envisage the relation between the spectral changes observed in the extinction spectra and the electronic transport through the molecules. Depending on the size and nature of the molecular linker two different modes, known as BDP (Bonding Dimer Plasmon) and CTP (Charge Transfer Plasmon), are excited. Furthermore, when the molecular linker has an excitonic resonance, new spectral features emerge due to the plasmon-exciton coupling.

The enhancement of light extraction is one of the major challenges for state of the art LEDs. Beside conventional approaches like surface roughening, metal gratings and metal nano particles offer an alternative approach for tailoring the optical properties of LEDs. The article will summarize theoretical calculations, experimental results and fabrication issues of plasmonic structures on inorganic LEDs. Furthermore a benchmark with state of the art LEDs will be given.

This work describes the design of a new plasmonic device made of gold nanoparticles separated from a gold film through a thermoresponsive polymer layer. This organic polymer responds to temperature variations by conformational changes (with a characteristic temperature called the lower critical solution temperature, LCST) and is therefore able to vary the distance between the gold nanoparticles and the gold film. The optical properties of these stimulable substrates were probed by Surface Enhanced Raman Scattering spectroscopy (SERS) using methylene blue (MB) as a molecular probe. We show that an increase of the external temperature reversibly induces a significant enhancement of the MB SERS signal. This was attributed to a stronger interaction between the gold nanoparticles and the gold substrate. The temperature-responsive plasmonic devices developed in this work thus provide a dynamic SERS platform, with thermally switchable electromagnetic coupling between the gold nanoparticles and the gold surface.

We use simultaneous electronic transport and optical characterization measurements to reveal new information about electronic and optical processes in nanoscale junctions fabricated by electromigration. Comparing electronic tunneling and photocurrents allows us to infer the optical frequency potential difference produced by the plasmon response of the junction. Together with the measured tunneling conductance, we can then determine the locally enhanced electric field within the junction. In similar structures containing molecules, anti-Stokes and Stokes Raman emission allow us to infer the effective local vibrational and electronic temperatures as a function of DC current, examining heating and dissipation on the nanometer scale.

In this work, we pave the route towards the engineering of strong and spectrally sharp Fano resonances in plasmonic nanostructures and derive analytical formulas for their line shape as a function of their electromagnetic response. Contrary to the original work of Fano, the formalism proposed here includes losses in the materials composing the system. As a result, a more general formula is obtained for the response of the system and general conclusions for the determination of the resonance parameters are drawn, in particular on its width and asymmetry. Using a surface integral simulation technique for electromagnetic scattering on three-dimensional individual and periodic nanostructures, we numerically validate our model for structures that are currently under extensive investigation in the plasmonic and metamaterial communities. The insights into the physical comprehension of Fano resonances gained this way will be of great interest for the design of plasmonic sensing platforms and metamaterials.

Spin-Hall effect is a basic phenomenon arising from the spin-orbit coupling of electrons. In particular, the spatial trajectory of the moving electrons is affected by their intrinsic angular momentum. The optical spin-Hall effect (OSHE) - beam deflection due to the optical spin (polarization helicity) - was recently presented. The effect was attributed to the optical spin-orbit interaction occurring when the light passes through an anisotropic and inhomogeneous medium. Here, we present and experimentally observe the OSHE in coupled localized plasmonic chains. The OSHE is due to the interaction between the optical spin and the path of the plasmonic chain with an isotropic plasmonic mode. In addition, OSHE was observed due to the interaction between the optical spin and the local anisotropy plasmonic mode, which is independent on the chain path. A spin-dependent orbital angular momentum was observed in a circular path. Moreover, a wavefront phase dislocation due to the scattering of surface plasmons from a topological defect is directly measured in the near-field by means of interference. The dislocation strength is shown to be equal to the incident optical spin and with analogy to the magnetic flux parameter in the Aharonov-Bohm effect. OSHE in spontaneous emission was also obtained in a structure consisting of a coupled thermal antenna array. The effect is due to a spin-orbit interaction resulting from the dynamics of the surface waves propagating along the structure whose local anisotropy axis is rotated in space. The OSHE in the nanoscale provides an additional degree of freedom in spin-based optics.

The local electric field distribution of propagating surface plasmons along Ag nanowires can be imaged by coating the nanowires with a layer of quantum dots, which provide a useful tool to study the plasmon propagation. In simple photonic networks composed of Ag nanowires, plasmons can be controllably routed to a specific nanowire output. The underlying physical mechanism is that the plasmon interferences modulate the near field distribution and thus control the output intensity. The plasmon interference can result in combinations of optical signals that execute specific interferometric Boolean logic operations. And a complete family of Boolean logic gates is realized in the simple nanowire networks. The primary nanowire in the network can be viewed as the plasmonic equivalent of a bus in a central processing unit. Furthermore, a plasmonic NOR gate is demonstrated by cascading OR gate and NOT gate. To realize the cascaded NOR gate, the plasmon wave packet should overlap with the junction between the main wire and the branch wire for the control signal.

An upgrade for the efficiency proven electromagnetic simulation tool, Multiple Multipole Program (MMP) is proposed, in order to efficiently analyze plasmonic structures in layered geometries. In this upgrade, a new expansion set, the layered media Green's function, is included in the open source EM simulation package Open- MaX, which contains the latest version of MMP. By this upgrade the advantages of both the MMP and layered media Green's functions are combined and an efficient and robust simulation tool for the analysis of structures in layered geometries in optical range of the spectrum is obtained. In this paper, the fundamentals of MMP and the derivation of layered media Green's functions will be discussed. Numerical results will also be included in order to demonstrate the efficiency of the upgraded method.

Raman spectroscopy is an extremely powerful analytical tool. Surface enhanced Raman scattering (SERs) enables sample sensitivity to extend down to the single molecule level. There is presently great interest in using uniform nanostructured surfaces to give reproducible and strong surface enhanced Raman (SER) signal. The nanocavities studied here have spherical cap architecture and are arranged uniformly in an Au array. These structures support both localised and delocalised plasmons. Localised surface plasmon polaritons exist inside the nanocavities and delocalised or propagating surface plasmon polaritons exist on the flat surface of the sample (Bragg plasmons). The angle dependence property of surface enhanced Raman is used in the present work to enable comparison between SERs caused by localised plasmons and SERs caused by delocalised plasmons. The samples used here were modified to enable separate investigations of the two plasmon types. The externally modified array had dye placed only on the flat top surface of the array. The internally modified array had dye placed only on the internal walls of the cavities. Results show that the changes in Raman intensities with respect to the incident angle depend on the location of dye on the array.

The optical near-field of lithography-defined gold nanostructures, arranged into regular arrays on a gold film, is characterized via ablation of a polymer coating by laser illumination. The method utilizes femto-second laser pulses from a laser scanning microscope which induces electrical field enhancements on and around the gold nanostructures. At the positions of the enhancements, the ablation threshold of the polymer coating is significantly lowered creating subdiffractional topographic modifications on the surface which are quantified via scanning electron microscopy and atomic force microscopy. The obtained experimental results for different polymer coating thicknesses and nanostructure geometries are in good agreement with theoretical calculations of the near field distribution for corresponding enhancement mechanisms. The developed method and its tunable experimental parameters show that the different stages in the ablation process can be controlled and characterized making the technique suitable for characterizing optical near-fields of metal nanostructures.

With the goal of improving photo-absorption of photovoltaic device and for plasmonic application we have fabricated nanopillar black silicon devices through etching-passivation technique which does not require any photomask and whole wafer scale uniformity is achieved at room temperature in a short time. We have carried out thorough optical characterization for nanopillar black silicon devices to be used for solar cell and plasmonic applications. Cathodoluminescence (CL), current dependent CL spectroscopy, photoluminescence (at room temperature and 77 K), Raman spectroscopy, reflectance and absorption measurement have been performed on the device. A thin layer of Ag is deposited to render with plasmonic property and the plasmonic effect is probed using surface plasmon enhanced fluorescence, angle dependent reflectance measurements, high resolution cathodoluminescence (CL), surface enhanced Raman spectroscopy (SERS) measurement and Fluorescence Lifetime Imaging Microscopy (FLIM) experiment. We obtained reduction in optical reflection of ~ 12 times on b-Si substrate from UV to NIR range, the nanostructured fluorescence enhancement of ~40 times and the Raman scattering enhancement factor of 6.4×10⁷.

We investigated the optical properties of ZnO/Ag grating structures, with the periods of 1000 and 1400 nm, fabricated by sputtering and nanoimprint lithography. The grating structures exhibited multiple peak features in visible-range photoluminescence (PL) spectra. Whereas a ZnO/Ag planar thin film showed two broad PL peaks in UV and visible region. Moreover, the PL intensity of the periodic structures was ~100 times larger than that of the planar counterpart. Several reflectance dips in the visible range were seen only in the grating structures, which could be caused by photoninduced surface plasmon polariton (SPP) excitation via the grating coupling. The PL peaks well matched with the reflectance dips. This represented that the PL enhancement should be originated from the SPP excitation. The finitedifference time-domain simulations also supported the plasmonic effects in the periodic structures.

Localized surface plasmon resonances (LSPR) govern the optical properties of metallic nanoparticles at the nanoscale level and depend strongly on their shape, size and environment. When particles are a few nanometers apart, new plasmon modes, that can be either bright or dark, arise from the electromagnetic coupling of the plasmon modes of the individual nanoparticles. In the case of 3 gold nanorods assembled in a dolmen-like structure, a transmission window has been observed experimentally from 0.9 and 1.3 eV. It has been attributed to Fano interferences between a broad bright mode coming from the monomer and a narrow dark mode coming from the dimer. Because it is optically inactive, the latter has to be probed locally with an electron beam. This is why we investigate numerically the energy electron loss (EEL) response of coupled metallic nanorods together with their optical properties to get insight into the origin of these Fano resonances. To achieve this, calculations are performed in the frame of the discrete dipole approximation both for optical and EEL excitations.

We examine the propagation of plasmonic TM (Transverse Modes) modes generated in the designed periodic array of silver (Ag) embedded on silicon (Si) substrate. The properties of surface plasmons are tailored by altering the size of Ag nanorods and its periodicity. Conventional waveguides cannot guide electromagnetic energy below the diffraction limit of light, which can be overcome by texturing the metal or dielectric surface. In this hybrid design we have textured the interface by placing metallic, Ag nanorods on Si substrate placed over bilayer system of glasses. This provides the missing momentum required, since SPP modes always lay beyond the light line and has shown strong confinement of light. Ag nanorods are structured at nano dimensions to control and manipulate surface plasmon polariton (SPP) propagation and thus open new possibilities in light matter interaction.

We study plasmonic cavity in a 1D array of asymmetric T-shaped plasmonic gratings. The asymmetric T-shaped plasmonic grating contains a silver bigrating structure. The first metallic grating contains the post of the T-shaped structure embedded in SiO2 and the second metallic grating is the cap of the T-shaped structure embedded in air. The bigrating can open a large plasmonic band gap (~ 0.15eV). We introduce a defect in a 1D array of asymmetric T-shaped structure by reducing the width of the cap in one line or in multiple lines. We have studied two kinds of defects. The first defect is a missing line from the T-shaped grating and it has a relatively low quality factor of 64 and a very small effective mode area [0.026 (λ/n)²]. The second one is done by removing or shifting more than one line from the T-shaped grating to make a gentler confinement and it leads to an enhancement of the quality factor (~200) and a slight increase in the effective mode area to [0.0375 (λ/n)²].

Due to their surface plasmon resonance silver nanoparticles are known to absorb visible light and give glasses various colors. Grown in mesoporous titania films, they give the material a photochromic behaviour that can be used to produce rewritable data carriers. On the one hand, UV light forms silver nanoparticles thanks to the photo-induced generation of electrons by titania matrix. On the other hand, visible light oxidizes the silver nanoparticles via the photoexcitation of electrons on Ag and their stabilization by oxygen molecules. The well controlled porosity of the mesoporous films allows to tune the nanoparticles size and to obtain, under UV illumination, homogenous distributions of small nanoparticles embedded within the titania matrix, which color the films. As all nanoparticles absorb light similarly, the film can then be completely bleached under exposure to a visible laser beam whose wavelength falls in the SPR band of the particles. Therefore, CW UV and visible focused-laser radiations, respectively, can repeatedly print and completely erase colored micropatterns within TiO₂/Ag films. The paper shows patterns printed under different conditions, deals with the reproducibility of the process and the inscription stability, and explains the nanoscale mechanisms, including silver migration during exposures, leading to the reversible color changes on the basis of TEM, SEM, absorption spectroscopy and Raman micro-spectroscopy characterizations. This paper also evidences that CW laser illuminations at higher intensity locally crystallize the titania matrix and investigates the influence of the absorption-induced heating around nanoparticles.

In this paper, long range surface plasmon devices using metallic subwavelength gratings are experimentally demonstrated. Subwavelength gold gratings are fabricated with deep UV interference lithography. Long range surface plasmon device using these subwavelength gold gratings is characterized by measuring the surface plasmon resonance reflectance curve in an attenuated total reflection setup. Surface plasmon resonance curve with approximately ten times narrower angular width than that from long range surface plasmon propagating along metallic thin films has been observed experimentally..

We present a powerful technique to fully characterize individual gold nanorods by using confocal microscopy in combination with higher order laser modes. We obtain topological information far beyond the optical resolution limit, although the used method is diffraction limited. We perform, for the first time, the imaging of gold nanorods by recording simultaneously their scattering and luminescence signal. In the future, this might permit to extent the results achieved already in [1] to a 3D system. Moreover, the scattering pattern is strongly dependent on the phase relation between the light scattered and reflected at the sample interface, while the luminescence pattern does not depend on this phase relation. By exploiting an index matched sample geometry, we were able to omit the phase relation and therefore detect the pure scattering signal and qualitatively compare it with the luminescence one. Furthermore, as previously shown [2, 3], our technique is capable to track the rotation of single noble metal nanorods. We show that measuring the rotation rate of gold nanorods might be useful to estimate the local viscosity of the surrounding medium.

In this paper, a unique nanoscrew Si structure is presented. The nanoscrew surface is made by anodized aluminum oxide (AAO) mask formation followed by extended deep reactive ionic etching (DRIE). Dense random zig-zag pillar structures that represent screw shapes are formed, with 1 um in height and the bottom base width ranging from 100 nm to 250 nm. The tip of the nanoscrews have radius of curvature even lower than 10 nm. The apparent naked-eye view of the nanoscrew surface, which only consists of nanopatterned N-type single crystalline Si is diffusively green. The optical properties of nanoscrew Si with and without metal deposition is presented as discussion in applications for SERS.

Tb, Yb, and Ag co-doped glass nano-composites were synthesized in a lithium-lanthanum-aluminosilicate glass matrix (LLAS) by a melt-quench technique. Ag nanoparticles (NPs) were formed in the glass matrix and confirmed by optical absorption and transmission electron microscopy (TEM). Plasmon enhanced luminescence was observed. Cooperative infrared to visible upconversion and visible to near-infrared quantum cutting were studied for samples with different thermal annealing times. Because the Yb³⁺ emission at 940 - 1020 nm is matched well with the band gap of crystalline Si, the quantum cutting effect may have its potential application in silicon-based solar cells.

We propose a novel and cost-effective copper-gold planar nanostructure resulting in strong plasmonic enhancement of the electromagnetic field with a peak at 615 nm and FWHM of 180 nm. The structure consists of aggregates of 20 nm in diameter gold nanospheres on a thin continuous 50 nm thick copper film. We attribute the strong field enhancement to the coupling of interparticle plasmon resonances from gold nanospheres to the surface plasmons induced in the copper film. The high reflectivity of the copper layer increases the collection efficiency in a reflection mode of the scattered light that would otherwise be transmitted. We achieved the homogeneity and planarity of the copper-gold structure through the electrostatic attraction between the negative surface charge of gold nanospheres and a lattice of positive copper ions of copper oxide, formed by ionic bonds during the exposure of copper to air.

Adding holes in a periodic arrangement to metallic thin films greatly affects the optical properties of the metal film. The compound structure can exert a large influence on electromagnetic fields that interact with the hole array. Many parameters affect the actual response of the hole arrays to electromagnetic fields, such as the periodicity, the size of the holes and their shape. Here, we will show by calculation that the angular emission and lifetime of emitters, embedded in hole arrays comprised of rectangular holes with varying aspect ratio, depend strongly on the hole aspect ratio. Specifically, changing the aspect ratio of the holes leads to a large variety in far-field emission patterns and a more than 10-fold changes in decay rate of a single emitter placed in the central hole of such an array.

Extraordinary optical transmission through metallic gratings is mediated by Fabry-Perot cavity modes inside the apertures and surface waves propagating along the grating. Anomalous features arise in the grating transmission spectrum when the optical period for the surface wave is equal to the grating pitch. The surface waves can be plasmonic in nature or due to diffracted orders propagating parallel to the surface. At optical frequencies, plasmonic effects are well separated from Wood-Rayleigh anomalies. The plasmonic band gap properties were determined with COMSOL by propagating a plasmon on a smooth Ag surface followed with a section containing a series of air gaps. The reflection spectrum for the plasmons shows a well defined frequency gap for plasmon propagation. The COMSOL simulations for light transmitted through the grating reveal anomalies in the vicinity of the plasmonic band gap. At the center frequency of the gap where surface waves are forbidden, the transmission through the grating is very low and the reflection is 98%. Standing waves are formed at the band edges and the fields become localized. At the high energy band edge the electric field localizes in the low index medium and the magnetic field in the high index medium. The field localization reverses at the low energy band edge. As a result of the localization at the band edges, the surface plasmons couple strongly to the Fabry-Perot cavity modes at the high energy band edge leading to enhanced transmission through the grating with the opposite properties for the low energy band edge.

The absorption spectra of different aqueous dispersions containing silver nanoparticles were computed by finite element method and compared to spectra determined by UV-Visible spectroscopy. This comparative study proved that the spectrum measured on the aqueous dispersion of bare silver nanoparticles with absorptance maximum at λ_meas = 391 nm corresponds to the characteristic UV surface plasmon band of spherical nanoparticles with 8.25 nm diameter. The presence of aggregates in aqueous dispersions resulted in splitting on the spectrum, when the surface of the silver nanoparticles with c_Ag = 2×10^-4 M concentration was functionalized by L-cysteine with cCys=5.7×10^-6 M concentration. The simplest aggregate-geometries that exhibit resonance at the measured absorptance maxima were determined by varying the number of silver nanoparticles, and the inter-particle distance in linear chains, and taking 0.45 nm thick cysteine-shell into account. The FEM computations proved that the primary maxima in the UV involve quadrupolar modes, while the secondary maxima red-shifted to λ_{meas_2}=567 nm at pH=2.98 and λ_{meas_2}'=588 nm at pH=4.92 originate from coupled dipolar plasmon resonances on extended aggregates aligned along the E-field oscillation direction. The non-aggregated particles and the aggregates rotated with respect to the E-field oscillation direction significantly contribute to the UV peak.

We compare two designs of metallodielectric stacks (MDS) based on Ag/GaP and Au/GaP, and calculate their superresolving bandwidths. The super-resolving bandwidth of the Ag/GaP design is (520nm-560nm), while that of Au/GaP is (630nm-660nm). We evaluate these two designs in their ability to resolve two 20nm wide apertures separated by a center-to-center distance of 80nm. We also compare two numerical techniques used to study these systems, namely the transfer matrix method (TMM) and the finite element method (FEM). The TMM is simpler than more numerically demanding FEM technique but FEM is more robust for determining super-resolution in most cases. Finally we discuss the practical limitations of our super-resolving imaging devices in resolving objects that are much smaller than the incident wavelength.

In this paper, we used PEDOT:PSS(Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)) as light sensing material with enhanced sensitivity by localized surface Plasmon resonance generated by gold nanoparticles . PEDOT:PSS was spin coated on ITO glass substrate and 120 nm of Al were evaporated above the PEDOT:PSS. The electrical properties of PEDOT:PSS was then enhanced after adding the gold nanoparticles between the ITO glass substrate and the film of PEDOT:PSS . We observed that the sample with gold nanoparticles has lower resistance when the samples were lighted. Compared with no illumination, the sample resistance (with naonparticles) decreased about 70%. This is not observed in the sample without gold nanoparticles. And when the density of the gold nanoparticles was increased, the total resistance of the sample was further decreased. When the sample with naonparticles was illuminated at different wavelengths , the total resistance of the sample was distinct. We measured the current intensity at 0.5 voltage at various wavelengths , and we can obtain that the current intensity correlate with the surface Plasmon resonance frequency of gold nanoparticles .

We show the effects of hole shape, size, and periodicity variation on extraordinary transmission through a tuned metamaterial of 4 pairs of alternating layers of Ag-Al₂O₃ with 20 nm thicknesses under illumination of TM light. The advantage of a metamaterial over a Ag film of similar thickness is the tunability of the surface plasmons coupling k-vector. Because their cross sections appear the same in fourier space, incident TM light sees the same structure for circular, square, and rectangular holes transmission is unaffected by these shape variations. Further, as we increase the hole size, the transmission does not exhibit the expected enhancement as both the 250 nm and 150 nm diameter holes are both too small to have their maxima overlap with the tuned transmission enhancement of the metamaterial. For the metamaterial, we are able to tune it to support surface plasmons from periodicities ranging from 130 nm to 215 nm, which effectively shifts the transmission peaks from the blue end of the spectrum in Ag films across the visible and into the red.

We have studied and analysed in this paper, the modeling of single-walled carbon nanotubes (SWNTs) optical and electrical properties utilizing terahertz (THz) time-domain spectroscopy in the frequency range of 0.1-2 THz. We have compared the measurement data of the THz power absorption coefficient, index of refraction and conductivity of SWNTs film with the experimental results obtained in Ref. [9], being our results based on the combination of Drude- Lorentz and Maxwell-Garnett models. Since we suppose the SWNTs network as an effective medium embedded in air, the comparison shows good agreement.

A technique capable of characterizing the spectral parameters of gold nanostructures is demonstrated. These properties are providing numerous advances in the field of high sensitive diagnostics, drug delivery and optical therapeutic applications. To obtain spectroscopic measurements of gold nanorods within a turbid media that mimics soft tissue, this work presents the potential of the photon to ultrasound conversion, by means of real-time Laser Optoacoustic Spectroscopy (LOS), The obtained results are shown for the complete wavelength range of 410 to 1000 nm that followed by a comprehensive comparative analysis with achieved results of parallel reference measurement schemeand standard spectrophotometry.

In the band structure analysis of photonic crystals it is normally assumed that the full photonic gaps could be found by scanning high-symmetry paths along the edges of Irreducible Brillouin Zones (IBZ). We have recently shown [1] that this assumption is wrong in general for sufficiently symmetry breaking geometries, so that the IBZ is exactly half of the complete BZ. That minimal required symmetry arises from the requirement on time-reversal symmetry. In this paper we show that even that requirement might be broken by using gyro-magnetic materials in the composition of photonic structures we can observe that the IBZ extends fully to the boundaries of the complete BZ, that is IBZ must be as the same as BZ.

Traditional mirrors at optical wavelengths use thin metalized or dielectric layers of uniform thickness to approximate a perfect electric field boundary condition. The electron gas in such a mirror configuration oscillates in response to the incident photons and subsequently re-emit fields where the propagation and electric field vectors have been inverted and the phase of the incident magnetic field is preserved. We proposed fabrication of sub-wavelength-scale conductive structures that could be used to interact with light at a nano-scale and enable synthesis of the desired perfect magneticfield boundary condition. In a magnetic mirror, the interaction of light with the nanowires, dielectric layer and ground plate, inverts the magnetic field vector resulting in a 0 degree phase shift upon reflection. Geometries such as split ring resonators and sinusoidal conductive strips were shown to demonstrate magnetic mirror behavior in the microwave [1] and then in the visible [2]. Work to design, fabricate and test a magnetic mirror began in 2007 at the NASA Goddard Space Flight Center (GSFC) under an Internal Research and Development (IRAD) award. Our initial nanowire geometry was sinusoidal but orthogonally asymmetric in spatial frequency, which allowed clear indications of its behavior by polarization. We report on the fabrication steps and testing of magnetic mirrors using a phase shifting interferometer and the first far-field imaging of an optical magnetic mirror.