This PDF file contains the front matter associated with SPIE Proceedings Volume 7757, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

A trimer of gold particles 50 nm in diameter is illuminated in oblique incidence by a plane wave. It is shown that one can fully focus light in only one nanogap and that the localization of the hot spot between the two nanogaps is controlled via the angle of incidence of the illuminating plane wave. The physical mechanism of this surprising phenomenon is unveiled. It relies on the excitation of opposite and in phase modes. Furthermore, balancing of the fundamental modes of the system permits to extinguish the dipolar moment of a metallic particle.

Surface-enhanced Raman scattering (SERS) from trinitrotoluene and other nitro-based explosives is important for the development of a reliable detection scheme exhibiting low false-positive rates. However, the interaction of these compounds with Ag and Au causes the molecules to orient in ways such that the primary vibrations of the nitro groups, the main identifying Raman marker of these compounds, are inhibited in addition to causing a reduction in the SERS response. It has recently been shown that cysteamine, which contains amine functional end groups, will electrostatically attract the nitro groups of TNT. Therefore, as the thiol functional group of cysteamine chemically bonds this molecule to the plasmonically-active Au and Ag nanoparticles studied, SERS of TNT can be obtained following the nitro-amine functional group complex formation. It is observed that the cysteamine adsorbs in one of two configurations on the metal surface, with the trans configuration consisting of bonding at the S end of the molecule and the cysteamine is perpendicular to the metal surface, while in the Gauche configuration S bonding occurs, but the molecule bends over towards the metal film surface, approaching the parallel configuration allowing the amine groups interact with the surface. We find that the trans configuration is best for the detection of SERS from TNT. Experiments compare well with DFT calculations of the cysteamine and TNT complex and their adsorption on Ag.

Although plasmonic nanoparticles are widely utilized in spectroscopy and sensing applications, a quantitative structure-function relationship is lacking. In this proceeding, we discuss measurements of single noble metal nanoparticles using localized surface plasmon resonance (LSPR) spectroscopy, surface-enhanced Raman spectroscopy (SERS), and transmission electron microscopy (TEM) to elucidate structure-function relationships. A recently developed LSPR imaging spectroscopy instrument with an extremely fast camera enables measurement of diffusion constants for individual silver nanoprisms dispersed in water-paving the way for plasmonic particles as dynamic labels in biological systems. Correlated studies involving two or all three of these techniques relate optical properties of the same nanoparticle to its structure. Lastly, single-molecule surface-enhanced Raman spectroscopy of Rhodamine 6G is explored on lithographically fabricated plasmonic structures.

Nanoparticle probes for use in targeted detection schemes and readout by surface-enhanced Raman scattering (SERS) comprise a metal core, Raman reporter molecules and a protective shell. One design of SERS labels specifically optimized for biomedical applications in conjunction with red laser excitation is based on tunable gold/silver nanoshells, which are completely covered by a self-assembled monolayer (SAM) of Raman reporters. A shell around the SAM-coated metal core stabilizes the colloid and prevents particle aggregation. The optical properties and SERS efficiencies of these plasmonic nanostructures are characterized both experimentally and theoretically. Subsequent bioconjugation of SERS probes to ligands such as antibodies is a prerequisite for the selective detection of the corresponding target molecule via the characteristic Raman signature of the label. Biomedical imaging applications of SERS-labeled antibodies for tumor diagnostics by SERS microscopy are presented, using the localization of the tumor suppressor p63 in prostate tissue sections as an example.

Silver nanorod arrays with different lengths fabricated by oblique angle deposition at various vapor deposition angles have been studied systematically by surface-enhanced Raman scattering (SERS). The SERS response of those substrates strongly depends on the length of the nanorods and the deposition angle, and the highest SERS enhancement factor can reach close to 10⁹. The reflections of the support substrate where the Ag nanorods are grown directly affect the SERS enhancement. In addition, the SERS response strongly depends on the incident configuration of the excitation beam, such as polarization and incident angle. We also find that the probe molecules on the side surface of nanorods contribute the most to the SERS intensity. This is due to the anisotropic optical properties of nanorods and the thickness of the nanorods. This study demonstrates that the Ag nanorod arrays are highly sensitive, uniform, and stable SERS substrates, and its SERS mechanism depends on the complex nanorod film geometry.

We will examine progress in electrically pumped Metal-Insulator-Metal (MIM) waveguide laser devices. Such structures allow the concentration of both electrically injected carriers and the optical mode into a gain region of just a couple of tens of nanometers in size in two dimensions. We will show results from such waveguide devices, demonstrating the presence of propagating optical modes in these devices. Another aspect of MIM waveguides is their use in Bragg gratings to form distributed feedback lasers. Results will be shown from such Bragg grating devices and key issues in their design discussed.

Laser science has tackled physical limitations to achieve higher power, faster and smaller light sources. The quest for ultra-compact laser that can directly generate coherent optical fields at the nano-scale, far beyond the diffraction limit of light, remains a key fundamental challenge. Microscopic lasers based on photonic crystals3, metal clad cavities4 and nanowires can now reach the diffraction limit, which restricts both the optical mode size and physical device dimension to be larger than half a wavelength. While surface plasmons are capable of tightly localizing light, ohmic loss at optical frequencies has inhibited the realization of truly nano-scale lasers. Recent theory has proposed a way to significantly reduce plasmonic loss while maintaining ultra-small modes by using a hybrid plasmonic waveguide. Using this approach, we report an experimental demonstration of nano-scale plasmonic lasers producing optical modes 100 times smaller than the diffraction limit, utilizing a high gain Cadmium Sulphide semiconductor nanowire atop a Silver surface separated by a 5 nm thick insulating gap. Direct measurements of emission lifetime reveal a broad-band enhancement of the nanowire's exciton spontaneous emission rate up to 6 times due to the strong mode confinement and the signature of apparently threshold-less lasing. Since plasmonic modes have no cut-off, we show downscaling of the lateral dimensions of both device and optical mode. As these optical coherent sources approach molecular and electronics length scales, plasmonic lasers offer the possibility to explore extreme interactions between light and matter, opening new avenues in active photonic circuits, bio-sensing and quantum information technology.

The metallic superlens of a single negative permittivity is easier to implement than the double negative material superlens and can be applied to nano-scale resolution lithography. The metallic superlens amplifies by the resonance the surface plasmon polariton (SPP) waves, which carry the sub-wavelength detail information of the object. However, the excitations of the long- and the short-range SPP modes of the metal slab lead to two peaks in the transfer function which enhance the spatial frequencies disproportionally, resulting in strong sidelobes in the image. Conventionally the metallic superlens is designed by trials without rules to follow. We propose to design the metallic superlens by approaching the cutoff condition of the long-range SPP mode in order to flatten the transfer function and to improve the imaging performance significantly. Design experiments of Al and Ag superlens with both the transfer-matrix approach and the numerical Finite Difference in Time Domain method are shown.

The Surface Plasmon Resonance (SPR) is a label-free, highly sensitive and real time sensing technique and has been extensively applied to biosensing and assay for decades. In a conventional SPR biosensor, a prism is used to create the total reflection in which the evanescent wave can excite the surface plasmon mode at the metal-dielectric interface at certain angle, at which condition the reflectivity of incident TM-polarized vanished as measured by a far-field photodetector. This is the optical detection of surface plasmon resonance. In this research, zinc oxide (ZnO) was used as the dielectric thin-film material above the gold surface on the glass substrate to form a co-plane Schottky diode; this structure is designed to be an alternative way to detect SPR. The strength of plasmonic field is possible to be monitored by measuring the photocurrent under the reverse bias. According to our experimental results, the measured photocurrents with TM-polarized illumination (representing the SPR case), TE-polarized illumination (non-SPR case) and no illumination conditions under DC -1.5V bias are -76.158mA (2.5μA), -76.085mA (3.6μA) and -76.089mA (3.4μA), respectively. Based on the results, we have demonstrated this Schottky diode based co-plane device has the potential to be used as the SPR detector and provides a possible solution for the need of a low-cost, miniaturized, electronically integrated, and portable SPR biosensor in the near future.

The history of optical solitons is fascinating and any theory of these has a weakly guiding foundation. Vortex generation and propagation properties have also a beautiful history, and the possibility of generating them together with magnetooptic control in plasmonic metamaterials will be discussed in detail. An emphasis will be placed on the fact that spatial solitons have a lot of application possibilities, especially when placed into the context of materials being used in a light-controlling light environment that is suitable for optical chips of the future. In addition, temporal solitons will also be invoked. An initial emphasis will be placed upon narrow beams and extremely short pulses, but it will be pointed out very strongly that detailed control of light-packets can also be introduced by using plasmonic metamaterials in the optical frequency range. This feature requires an exact study of wave propagation in waveguides that are possibly tapered, or simply just power controlled. To any designs that are proposed can be added the advantage of using magnetooptics. The complicated structures that will be examined will include soliton-like channels near interfaces. Optically linear and nonlinear metamaterials will be discussed in this context. The applications of the outcomes should lead to a new range of optical switching.

In this work, we study how to use a plasmonic dipole antenna as a multifunctional nanodevice for surface-enhanced Raman spectroscopy (SERS), localized surface plasmon resonance (LSPR) -based sensing and optical trapping. An analytical model is implemented to link the local electric field enhancement with the gradient forces, as well as the resonance shift caused by the presence of the analyte which can be a molecule or a nanoparticle. We find that a higher local field enhancement induces stronger trapping forces and a larger resonance wavelength shift. Experiments were also performed using plasmonic dipole antennas. Strong SERS signals were observed from the nanogap of an antenna, trapping of Au nanoparticles as small as 10 nm was achieved with a moderate laser power, and evident resonance shifts of the antenna associated with the trapping events were also observed. These results are consistent with our theoretical result that the giant field enhancement generated by a plasmonic dipole antenna also generates strong gradient forces and a high spectral sensitivity.

Arrays of "nanorectennas", consisting of nanodiode-coupled nanoantennas, are of interest for converting visible/near-infrared (vis/nir) light into useful direct current. For efficient energy conversion, the nanoantenna array must have a high absorbance (for different polarizations and angles of incidence) and a large fill factor; i.e., the nanoantennas must be tightly packed together. We fabricate hexagonal, close-packed (~ 100 nm nearest neighbor separation), large area (~ 1 cm²) arrays of vertical (e.g., perpendicular to the substrate) Au nanowires (length < 1 μm) on Si, by electrochemically depositing gold into a porous aluminum oxide template (a potentially inexpensive process scalable to large dimensions). Coupling of these nanowires causes a considerable blue-shift of the plasmonic resonance of a single Au nanowire when illuminated by p-polarized light from the infrared to the blue-green portion of the visible spectrum (similar to the s polarization resonance), enabling a nanorectenna with tuned response in the vis/nir regime, whose absorption is roughly polarization-independent and relatively insensitive to angle of incidence. We measure the off-normal reflectivity of these arrays, compare with simulations, and present experimental data on rectification and power generation in the attached Au-Si Schottky nanodiodes.

Chemically synthesized Ag nanowires (NWs) can serve as waveguides to support propagating surface plasmons (SPs). By using the propagating SPs on Ag NWs, the surface-enhanced Raman scattering of molecules, located in the nanowire-nanoparticle junction a few microns away from the laser spot on one end of the NW, was excited. The propagating SPs can excite the excitons in quantum dots, and in reverse, the decay of excitons can generate SPs. The direction and polarization of the light emitted through the Ag NW waveguide. The emission polarization depends strongly on the shape of the NW terminals. In branched NW structures, the SPs can be switched between the main NW and the branch NW, by tuning the incident polarization. The light of different wavelength can also be controlled to propagate along different ways. Thus, the branched NW structure can serve as controllable plasmonic router and multiplexer.

Nanophotonics is finding myriad applications in information technology, health care, lighting and sensing. Plasmonics, as one of the most rapidly growing fields in nanophotonics, has great potential to revolutionize many applications in nanophotonics, including bio-sensing, imaging, lighting, photolithography and magnetic recording. In this chapter, we explore the electrodynamics of plasmonic fields on different structured metallic chips and demonstrate how to manipulate light from nano to micro scale on the structure plasmonic chips. We investigate on-chip plasmonic metamaterials with novel material responses and functionalities in nanometers, develop the design methodology for plasmonic chips compatible with the conventional Fourier optical devices in microns and sub-millimeters, as well as construct sophisticated chip-scale integration of optical elements with feature sizes on different length scales.

A new class of optical modes arising from the hybridization between one localized plasmon and two orthogonal waveguide modes is described. Of particular interest is our observation that these hybrid modes simultaneously exhibit extremely low-loss and highly dispersive characteristics, which translate into slow light propagation. We propose that this is a new type of classical analogs of the electromagnetically induced transparency (EIT) in an atomic system. Based on a fine balance of geometric and material dispersion in the system, destructive interference of the waveguide modes cancels out the metal loss, resulting in a narrow transparent window within a broad absorption band. In accordance with the developed phenomenological model, we show that the dispersion characteristics of the hybrid modes can be entirely controlled by tuning the coupling strengths between the plasmon and waveguide modes while the mode losses remain the same.

We discuss how the intriguing phenomenon of surface plasmon resonance (SPR) can be exploited in enhancing the intensity field of the incident femtosecond laser for the purpose of high harmonic generation (HHG). We first summarize our previous attempt made with a 2-D planar nanostructure comprised of metallic bow-tie nano-antennas, which enabled us to generate up to 21st harmonics from Xenon gas using 1-nJ pulse energy with an intensity enhancement factor of ~20 dB. Then we describe another attempt currently being made by devising a 3-D nano-waveguide with the aim of improving the HHG conversion efficiency by expanding the localized volume of field enhancement by means of propagating surface plasmon polaritons (SPPs). Our finite-difference time-domain (FDTD) calculation shows that the enhanced volume can be increased significantly by optimal selection of the waveguide's geometrical parameters as verified in our preliminary experimental results.

We present a systematic investigation into the conditions required for the production of XUV light via nanoplasmonic enhanced high harmonic generation in metallic spheroids. Control over the temporal response of the plasmonic fields, and therefore the resulting XUV radiation, is achieved through the nanostructure configuration and the carrier envelope phase of the driving laser pulse. Coupled symmetric structures are shown to produce sufficient localized field enhancement and relatively long exponential plasmon decay times leading to the characteristic high harmonic spectra. In contrast coupled asymmetric structures have a much broader resonance and a highly non-uniform plasmon response in the temporal domain.

Here, we establish the principal limits for the nanoconcentration of the THz radiation in metal/dielectric waveguides and determine their optimum shapes required for this nanoconcentration. We predict that the adiabatic compression of THz radiation from the initial spot size of R₀ ~ λ₀ to the final size of R = 100 - 250 nm can be achieved with the THz radiation intensity increased by a factor of ×10 to ×250. This THz energy nanoconcentration will not only improve the spatial resolution and increase the signal/noise ratio for the THz imaging and spectroscopy, but in combination with the recently developed sources of powerful THz pulses will allow the observation of nonlinear THz effects and a carrying out a variety of nonlinear spectroscopies (such as two-dimensional spectroscopy), which are highly informative. This will find a wide spectrum of applications in science, engineering, biomedical research, environmental monitoring.

In this paper, we present a design for a widely tunable solid-state optically and electrically pumped THz laser based on the Smith-Purcell free-electron laser. In the free-electron laser, an energetic electron beam pumps a metallic grating to generate surface plasmons. Our solid-state optically pumped design consists of a thin layer of dielectic, such as SiN_x, sandwiched between a corrugated structure and a thin metal or semiconductor layer. The lower layer is for current streaming, and replaces the electron beam in the original design. The upper layer consists of one micro-grating for coupling the electromagnetic field in, another for coupling out, and a nano-grating for coupling with the current in the lower layer for electromagnetic field generation. The surface plasmon waves generated from the upper layer by an external electromagnetic field, and the lower layer by the applied current, are coupled. Emission enhancement occurs when the plasmonic waves in both layers are resonantly coupled.

Optical resonances in a single triangular-shaped metal groove and a periodic array of grooves are studied theoretically with the Green's function surface integral equation method. In the case of a single groove we study the geometric resonances for different groove heights, and show that the groove resonances can be explained by standing waves in the gap being reflected at both the closed groove bottom and the open groove top. We also present the reflection that will be obtained for different cases of picking up the reflected light within a small or large angular range. Large resonant fields at the groove bottom are explained as being due to nanofocusing by the groove which can also be thought of as a closed tapered gap. In the case of a periodic array of grooves we find that resonances of individual grooves are still present in near-field enhancement spectra and reflection spectra but there are also e.g. very sharp resonances (Rayleigh anomalies) at wavelengths near the cutoff wavelength of higher grating-reflection orders. Typical resonant enhancements can easily be two times higher compared with the case of a single groove. The resonances can be realized in the wavelength range from the visible to the infrared by varying groove height, angle, and periodicity.

We study the importance of taking the nonlocal optical response of metals into account for accurate determination of optical properties of nanoplasmonic structures. Here we focus on the computational physics aspects of this problem, and in particular we report on the nonlocal-response package that we wrote for state-of the art numerical software, enabling us to take into account the nonlocal material response of metals for any arbitrarily shaped nanoplasmonic structures, without much numerical overhead as compared to the standard local response. Our method is a frequency-domain method, and hence it is sensitive to possible narrow resonances that may arise due to strong electronic quantum confinement in the metal. This feature allows us to accurately determine which geometries are strongly affected by nonlocal response, for example regarding applications based on electric field enhancement properties for which metal nanostructures are widely used.

We develop a theory of cooperative emission of light by an ensemble of emitters, such as fluorescing molecules or semiconductor quantum dots, located near a metal nanostructure supporting surface plasmon. The primary mechanism of cooperative emission in such systems is resonant energy transfer between emitters and plasmons rather than the Dicke radiative coupling between emitters. We identify two types of plasmonic coupling between the emitters, (i) plasmon-enhanced radiative coupling and (ii) plasmon-assisted nonradiative energy transfer, the competition between them governing the structure of system eigenstates. Specifically, when emitters are removed by more than several nm from the metal surface, the emission is dominated by three superradiant states with the same quantum yield as a single emitter, resulting in a drastic reduction of ensemble radiated energy, while at smaller distances cooperative behavior is destroyed by nonradiative transitions. The crossover between two regimes can be observed in distance dependence of ensemble quantum efficiency. Our numerical calculations incorporating direct and plasmon-assisted interactions between the emitters indicate that they do not destroy the plasmonic Dicke effect.

Infrared absorption spectroscopy offers direct access to the vibrational signatures of molecular structure. Although absorption cross sections are nearly 10 orders of magnitude larger than the Raman cross sections, they are small in comparison with those of fluorescent labels. Sensitivity improvements are therefore required in order for the method to be applicable to single molecule/monolayer studies. In this work, we demonstrate a plasmon enhanced vibrational spectroscopy technique which allow for the measurement of molecule specific signatures at the monolayer level. Specifically, we show 4-5 order of magnitude enhancement of the amide-I and II backbone signature of protein monolayers, the signal resulting from only zeptomole quantities of molecules.

Surface-enhanced Raman scattering (SERS) and optical properties on quasi-3D gold nanohole arrays with precisely controlled size and shape (circle and triangle) were investigated. The nanostructures with circular nanoholes exhibit two to three orders of magnitude higher SERS signals than those with triangular nanoholes. While the enhancement factor (EF) varies with the diameter of nanoholes for circular shaped nanostructures and shows the maximum EF for the nanostructure with 300 nm diameter, the EF for triangular shaped nanostructures does not change with the length of triangles. The normal transmission spectroscopy of white light and the electric field distributions upon the illumination of a 785 nm laser were calculated using the three-dimensional finite-difference time-domain (3D-FDTD) method. The relationship between SERS optical properties such as normal transmission spectra, and electric field distributions was discussed The broad tunable quasi-3D plasmonic nanostructures could have great potential applications in chemical and biological sensors based on SERS platform with molecular identity.

We have studied characteristics of an optical resonator with two stubs as functional devices in a plasmon waveguide in order to realize compact integrated optical circuits. The resonator is consisting of two stubs set separately in the waveguide where the stub works as low loss mirror. Numerical simulation has clearly shown that the resonator process high Q value as a plasmonic resonator. We have also fabricated stub-type resonators in gap plasmonic waveguides, of which the gap width is around 150 nm, with stubs embedded in a silver thin film on a substrate by using FIB direct processing techniques. The characteristics of these structures have been observed experimentally from visible to near-infrared light. And we have successfully observed the resonance of the resonator in the transmission spectrum.

The absorption spectrum of a dielectric film with periodic array of metallic islands of different shapes and different mutual distances was studied analytically, numerically, and experimentally. We show that the positions of the surface plasmon resonances depend on the nano-structural details. We propose two ways of controlling plasmon resonance frequency: changing the aspect ratio of the elliptical or rectangular islands and changing their mutual distances. A new analytical asymptotic approach for calculating the optical properties of such plasmonic systems is developed. The results of our analytical and numerical studies are in good qualitative agreement with experiment.

Despite surface-enhanced Raman scattering (SERS) being first observed in the late 1970s, efforts to provide reproducible SERS-based chemical sensors have been hindered by the inability to make large-area devices with a uniform SERS response. Furthermore, variations in the observed spectra occur due to the variable interactions and orientations of the analyte with the textured SERS surfaces. Here we report on periodic arrays of Ag- and Au-coated vertical silicon nanopillars fabricated by e-beam lithography and reactive ion etching for use as SERS sensor templates that provide both large and uniform enhancement factors (up to 1×10⁸) over the structure surface area. We discuss the impact of the overall geometry of the structures, by varying both the diameter and the edge-to-edge spacing in an effort to optimize the SERS response for a given excitation laser wavelength. Calculations of the electromagnetic field distributions within such structures were also performed and support the behavior observed experimentally.

Transparent conductive electrodes are critical to the operation of optoelectronic devices, such as photovoltaic cells and light emitting diodes. Effective electrodes need to combine excellent electrical and optical properties. Metal oxides, such as indium tin oxide, are commonly used. There is substantial interest in replacing them, however, motivated by practical problems and recent discoveries regarding the optics of nano-patterned metals. When designing nano-patterned metallic films for use as electrodes, one needs to account for both optical and electrical properties. In general, it is insufficient to optimize nano-structured films based upon optical properties alone, since structural variations will also affect the electrical properties. In this work, we investigate the need for simultaneous optical and electrical performance by analyzing the optical properties of a class of nano-patterned metallic electrodes that is obtained by a constant-sheet-resistance transformation. Within such a class the electrical and optical properties can be separated, i.e., the sheet resistance can be kept constant and the transmittance can be optimized independently. For simple one-dimensional periodic patterns with constant sheet-resistance, we find a transmission maximum (polarization-averaged) when the metal sections are narrow (< 40 nm, ~ 10% metal fill-factor) and tall (> 100 nm). Our design carries over to more complex two-dimensional (2D) patterns. This is significant as there are no previous reports regarding numerical studies on the optical and electrical properties of 2D nano-patterns in the context of electrode design.

Plasmonic structures can be advantageous for single photon sources due notably to their large Purcell factor over a relatively large frequency range. Here, we compare thin disks and optical patch antenna configurations. We analyze the physics involved in the modification of the Purcell factor, and discuss how the structures can be seen as plasmonic cavities. We also discuss briefly the implications for single photon sources.

In this work we describe a dipole wave propagation through a two-dimensional nanoparticles array, where the array is doped with magnetic impurities randomly distributed. The effect of impurities is a trajectory resorting in the wave propagation; this phenomenon is described by means of the percolation theory.

In this work we describe a resonant interaction between nanoparticles considering the geometric parameters using a multidisciplinary approach to mode coupling theory. The study groups are differentiable equations describing the resonant processes.

A theoretical electrostatic approach for determination of plasmon eigenresonances and absorption cross section spectra of arbitrarily shaped metal nanoparticles with cylindrical symmetry in stratified geometries is presented. The method is based on a surface integral equation for the surface polarization charge density. From symmetry considerations and by incorporating all effects of the stratified surrounding into the Green's function we show how the three dimensional analysis can be reduced to a single integral over the polar angle along the surface of the metal nanoparticle. The theoretical scheme is exemplified by analyzing silver nanoparticles shaped as spheres, oblate spheroids, and nanodisks in different surroundings involving silicon. The effect of varying the distance between a silver sphere and a silicon surface on plasmonic eigenvalues and absorption cross section spectra is presented. By flattening silver oblate spheroids and nanodisks embedded in a homogenous silicon surrounding it is shown how the fundamental horizontally polarized plasmon resonance can be shifted into the near infrared wavelength range. Also the effect of varying the thickness of thin silicon films with silver nanoparticles embedded is presented. The results indicate that silver nanoparticles embedded in silicon could be interesting for plasmon assisted solar cells.

In this paper, we present a novel plasmonic substrate for both local preconcentration and surface enhanced Raman scattering (SERS) detection. The plasmonic substrate is fabricated by nanoimprint process and then overlaid a thin silver film to adjust the surface plasmon resonance wavelength. Both photothermal conversion and SERS-active wavelength are designed for He-Ne Laser. The measurement process includes three steps. First of all, local concentration is performed by laser induced heating on the plasmonic substrate (over 100°C) to create a small bubble in high power mode (10mW). Then turn off the laser, the target analyte (Rhodamine 6G solution) will concentrate to the center as the bubble disappeared. Finally, the SERS spectra are taken in low power mode (1mW). The intensity of SERS signal at the concentrated region is an order of magnitude larger than the untreated region. The repeatability of this preconcentration process makes it a good candidate to amplify small SERS signals especially for trace detections.

We present the formation of a singularity in k-space from a periodic metal-dielectric nanostructure. The singularity originates from the balance between alternating normal and anomalous coupling. By employing the formalism of Dirac dynamics for relativistic quantum particles, we theoretically describe propagation dynamics of surface plasmon polaritons and demonstrate a strong diffraction anomaly (conical-like diffraction) near the singular point.

Here we investigate the interaction of metallic nanoparticles which support localized surface plasmon resonances (LSPR). We use dark-field spectroscopy and normal-incidence transmission spectroscopy to investigate the scattering and extinction of metallic nanoparticles on their own and in both ordered and random arrays. We compare experimental results with theory based on the coupled dipole approximation (CDA) and the finite-element method (FEM). CDA is used to demonstrate the ability to indirectly measure the extinction of an individual particle by considering a sparse, disordered, finite array of particles.

A double-layered nano-aperture on metallic film composed of a large square aperture under a small bow-tie aperture is proposed. Numerical analysis of the proposed structure by using 3-dimensional finite difference time domain method showed that the transmission enhancement factor reached about 245 at 20 nm away from the metal surface compared to the incident intensity. Compared to the single-layered bow-tie aperture, the proposed structure had intensity about three times higher than that of single-layered one at the same resonant wavelength of 1200 nm. In addition, a near-field full width at half-maximum intensity spot size was about 56 nm in the x-direction and 64 nm in the y-direction. The enhancement factor of the proposed structure was mainly depending on the size of the additional square aperture. These properties can be adopted for nano-optical applications such as scanning near-field optical microscopy, optical data storage, nano-lithography, and bio-sensing.

Tb³⁺ and Ag co-doped glass nano-composites are synthesized in a glass matrix Li₂O-LaF₃-Al₂O₃-SiO₂ (LLAS) by a melt-quench technique. The nucleation and growth of Ag nanoparticles (NPs) were controlled by a thermal annealing process. A broad absorption band peaking at about 420 nm was observed due to surface plasmon resonance (SPR) of Ag NPs. Annealing of glass samples results in the growth of Ag NPs. Photoluminescence (PL) emission and excitation spectra were measured from glass samples with different Ag concentrations and different annealing times. Plasmon enhanced Tb³⁺ luminescence was observed at certain excitation wavelength regions. Luminescence quenching was observed for samples with high Ag concentration and longer annealing time. Our luminescence results suggest that there are two competitive effects, enhancement and quenching, acting on Tb³⁺ luminescence in the presence of Ag NPs. The enhancement of Tb³⁺ luminescence is mainly attributed to local field effects: the SPR of Ag NPs causes an intensified electromagnetic field around the NPs, resulting in enhanced optical transitions of Tb³⁺ ions in the vicinity. The quenching effect in the presence of Ag NPs suggests an energy transfer from Tb³⁺ ions to Ag NPs. The competition between the plasmonic enhancement and the quenching effect is discussed for samples with different Ag concentrations and annealing times.

Optical characteristic of a pair of subwavelength holes on metallic thin film has been studied by numerical simulation and FIB-assisted experiment. Each hole is in a square shape with four corners having fillets. One hole is set up adjascent to another by bringing the most pointed corners close to each other. As a result, a dividing wall between the holes has two v-channels on the both sides. When the hole pair is illuminated with laser beam having linear polarization perpendicular to alignment of the holes, surface plasmon polaritons (SPPs) are excited at the bottom of v-channels and propagate to the other edges of holes. Such the SPPs converge at the end of dividing wall and create a highly localized optical near-field like a point light source. The formation of intense spot is studied with systematic configuration and excitation parameters for the two holes by (1) three-dimensional electromagnetic field analysis for multi-layered model including the two holes, and (2) two-dimensional mode analysis for infinite metallic rod waveguide having the two holes near the center of itself, which are based on the proven finite element method (FEM) to solve partial differential equations (PDEs) for electromagnetic waves.

We produce and characterize randomly distributed, highly enhancing, large-area gold nanostructures formed on templates made after anodization of Al with either oxalic acid or phosphoric acid, producing nanoporous alumina films. The interpore distance of the fabricated templates can be tuned continuously, and by a subsequent selective dissolution of the upper film making up the porous Al₂O₃ layers, the remaining embossed barrier layer can be used as a template for sputter deposition of gold. The density (and structure) of gold nanoparticles covering the template is adjusted by varying the sputtering conditions. We directly correlate the strong and broad surface plasmon (SP) resonances investigated by reflection spectroscopy, as well as the field intensity enhancement (FE) factor investigated by far-field two-photon luminescence (TPL) scanning optical microscopy measurements, to the density of the randomly distributed gold nanoparticles on the templates. The position of high enhancements in the TPL-images and the magnitude of the average FE are dictated by the laser excitation wavelength. We relate this large-area massive enhancement to constructive interference of SP polaritons scattered from the densely packed gold particles on the fabricated templates.

Surface Plasmons Resonance (SPR) architectures based on grating coupler/disperser combination is an attractive alternative for spectral-based sensing. We present a new concept where the plasmon coupling occurs through thin film grating and sensing occurs via the first diffraction order in reflective or transmitive mode. The developed geometry is dedicated to droplet sensing. The extension of the architecture to bi-dimensional array of sensors is also facilitated. This paper describes several designs of sensors. The analysis of their theoretical performances is demonstrated and compared, including a sensitivity evaluation.

In this Letter we develop a theory of spoof plasmons propagating on real metals perforated with planar periodic grooves. Deviation from the spoof plasmons on perfect conductor due to finite skin depth has been analytically described. This allowed us to investigate important propagation characteristics of spoof plasmons such as quality factor and propagation length as the function of the geometrical parameters of the structure. We have also considered THz field confinement by adiabatic increase of the depth of the grooves. It is shown that the finite skin depth limits the propagation length of spoof plasmons as well as a possibility to localize THz field. Geometrical parameters of the structure are found which provide optimal guiding and localization of THz energy.

The goal of our project is to use computational methods, such as discrete dipole approximation (DDA) to study nanoparticles in biomedical photonics problems. Nanoparticle absorption and scattering are strongly affected by their shape, size, composition and dielectric environment. We focus on light scattering from nanoparticles embedded in biological or biocompatible media, such as water, glycerin and hemoglobin at erythrocyte hemoglobin concentration at concentration characteristic to intrinsic erythrocyte concentration. This method lets us consider complex refractive index of the nanoparticle and the surrounding medium as a function on the wavelength of light. We are interested in strong absorption and scattering around 800 nm that makes such nanoparticles potentially useful in biomedical applications, such as detection and curing cancer. Considering nanoparticles in living cells containing nanoparticles lets us understand light scattering from normal and pathological structures within biological tissue.

We demonstrate a convenient method to improve the surface Plasmon resonance sensitivity by manipulating the permittivity of active medium using metal-dielectric (Ag-SiO₂) composite monolayer. We demonstrate the successful permittivity engineering of SPR active medium in both theory and experiments. Based on the basic theory of SPR and Bruggeman effective medium theory (EMT), we theoretically confirm that the angular sensitivity enhances using manipulated permittivity of metal-dielectric composite layer.

Silver-doped titanium dioxide thin films were deposited on glass substrates by the sol-gel process. Undoped films and films doped with 1 mol% AgNO₃ were annealed at 100°C for 30 minutes and sintered at 520°C for 1 hour. The optical and morphological properties of the films were analyzed by optical absorption spectroscopy, X-ray diffraction and scanning electron microscopy. Two crystalline phases, anatase and rutile were identified in the films by X-ray diffraction. An absorption band was located at 415 nm which is associated to the surface plasmon resonance of the silver nanoparticles. This spectrum was modelled using the Gans theory considering small silver nanoparticles with diameters of 3 nm and a refractive index lower than that coming from host matrix.

Metallic nanospheres (Au, Ag, Cu) deposited on PV-active semiconductor surface can act as light converters, collecting energy of incident photons in plasmon oscillations. This energy can be next transferred to semiconductor substrate via a near-field channel, in a more efficient manner in comparison to the direct photo-effect. We explain this enhancement by inclusion of all indirect inter-band transitions in semiconductor layer due to near-field coupling with plasmon radiation in nanoscale of the metallic components, where the momentum is not conserved as the system is not translationally invariant. The model of nano-sphere plasmon is formulated (RPA, analytical version, adjusted to description of large metallic clusters, with radius of 10-100 nm) including surface and volume modes. Damping of plasmons is analyzed including Lorentz friction, and irradiation losses in far- and near-field regimes. Resulting resonance shifts are verified experimentally for Au and Ag (10-80 nm) colloidal water solutions with respect to particle size. Probability of interband transition (within the Fermi golden rule) caused by coupling to plasmons in near-field regime turns out to be 4-order larger than for coupling of electrons to planar-wave photons. Inclusion of proximity effects (for type of deposition of nano-components and their shape) allows for explanation of photo-current growth experimentally measured. We describe also a non-dissipative collective mode of surface plasmons in a chain of near-field-coupled metallic nanospheres, for particular size/separation parameters and wave-lengths.

Performances of surface biosensors are often controlled by the analyte delivery rate to the sensing surface instead of sensors intrinsic detection capabilities. In a microfluidic channel, analyte transports diffusively to the biosensor surface severely limiting its performance. At low concentrations, this limitation, commonly known as mass transport problem, causes impractically long detection times extending from days to months. In this proceeding, we propose and demonstrate a hybrid biosensing platform merging nanoplasmonics and nanofluidics. Unlike conventional approaches where the analytes simply stream pass over the sensing surface, our platform enables targeted delivery of analytes to the sensing surface. Our detection platform is based on extraordinary light transmission effect (EOT) in suspended plasmonic nanohole arrays. The subwavelength size nanoholes here act as nanofluidic channels connecting the microfluidic chambers on both sides of the sensors. In order to materialize our detection platform, we also introduce a novel multilayered micro/nanofluidics scheme allowing three dimensional control of the fluidic flow. Using our platform, we show 14-fold improvement in mass transport rate constant appearing in the exponential term. To fabricate these biosensors, we also introduce a lift-off free plasmonic device fabrication technique based on positive resist electron beam lithography. Simplicity of this fabrication technique allows us to fabricate nanostructures with ease, high yield/reproducibility and minimal surface roughness. As a result, we achieve higher refractive index sensitivities. This fabrication technique can find wide range of applications in nanoplasmonics field by eliminating the need for operationally slow and expensive focused ion beam lithography.

Metal enhanced fluorescence (MEF) has received much attention because of possible biomedical and sensing applications. MEF includes two mechanisms for fluorescence enhancement: (1) the enhanced electromagnetic field associated with surface plasmons increasing the excitation of fluorophores and (2) excited fluorophores radiating via induced surface plasmons. The second mechanism results in enhanced directional emission when fluorophores are located near a metal film or grating. This work focuses on gold wire gratings fabricated on a silica substrate coated with a layer of fluorophores. Previous studies on corrugated film gratings show that coupling to higher order as well as substrate side plasmon modes occurs with lower efficiency. We find for wire gratings, fluorophores couple to higher order plasmon modes on both the active and substrate side of the gold wires with uniform efficiency. We also measure directional enhanced fluorescence on both the active (reflection) and substrate (transmission) side of the gratings. Utilizing higher order modes allows gratings with micron and larger sized features to enhance fluorescence wavelengths in the visible range, greatly loosening fabrication requirements for potential applications. The ability to measure enhanced fluorescence in transmission also makes wire gratings appropriate for applications favoring a linear optical set up.

Analyses of the resonances of both symmetric and antisymmetric polarization states in pairs of tightly coupled nanoshells, made of either a gold-core/dielectric-shell or a dielectric-core/gold-shell, are carried out at optical frequencies. The nanoparticles are modeled as single electric dipoles, at first considering only the static (non retarded) field terms and resorting to closed-form expressions to investigate the transverse and longitudinal (with respect to the pair axis) plasmonic resonance frequencies of the nanoshell pair. These approximate resonance values are then compared to the ones obtained including all dynamical retarded field terms, and with full wave simulations. We also show how the additional degree of freedom provided by using nanoshells, in contrast to using solid metallic nanoparticles, can be exploited for tuning the symmetric and antisymmetric resonance frequencies in pairs of tightly coupled nanoshells. Indeed, optical resonances of nanoshells can be varied over hundreds of nanometers in wavelength, across the visible and into the infrared region of the spectrum, by varying the relative dimensions of the core and shell. This makes the pair suitable as a constituent for metamaterials since it supports an antisymmetric mode that can be interpreted as an effective magnetic dipole; therefore, it is useful for providing artificial magnetism in metamaterials that may support backward propagation or have equivalent high/low characteristic wave impedance. Furthermore, we show the field enhancement between the two nanoparticles which may find applications in surface enhanced Raman scattering. We also show how an incident field excites the transversal and longitudinal modes supported by the pair.

This study investigated theoretically and experimentally that two-photon excited fluorescence is enhanced and quenched via surface plasmons (SPs) excited by total internal reflection with a silver film. The fluorescence intensity is fundamentally affected by the local electromagnetic field enhancement and the quantum yield change according to the surrounding structure and materials. By utilizing the Fresnel equation and classical dipole radiation modeling, local electric field enhancement, fluorescence quantum yield, and fluorescence emission coupling yield via SPs were theoretically analyzed at different dielectric spacer thicknesses between the fluorescence dye and the metal film. The fluorescence lifetime was also decreased substantially via the quenching effect. A two-photon excited total internal reflection fluorescence (TIRF) microscopy with a time-correlated single photon counting device has been developed to measure the fluorescence lifetimes, photostabilities, and enhancements. The experimental results demonstrate that the fluorescence lifetimes and the trend of the enhancements are consistent with the theoretical analysis. The maximum fluorescence enhancement factor in the surface plasmon-total internal reflection fluorescence (SP-TIRF) configuration can be increased up to 30 fold with a suitable thickness SiO₂ spacer. Also, to compromise for the fluorescence enhancement and the fluorophore photostability, we find that the SP-TIRF configuration with a 10 nm SiO₂ spacer can provide an enhanced and less photobleached fluorescent signal via the assistance of enhanced local electromagnetic field and quenched fluorescence lifetime, respectively.

In this study, a three-dimensional (3D) polyacrylamide microstructure containing gold nanorods (AuNRs) was fabricated successfully by utilizing femtosecond laser-based two-photon polymerization (TPP) with a Rose Bengal (RB) photoinitiator, and can provide a great diversity of optical properties. To maintain AuNRs in the 3D polymer microstructures, the fabrication laser power can be significantly reduced to 1.0 mW by tuning the laser wavelength for the two-photon absorption of RB to improve TPP efficiency, but not for the longitudinal plasmon resonance of AuNRs to photothermally damage AuNRs. After the TPP processing, a higher laser power, greater than the threshold of the AuNR damage at the wavelength for the longitudinal plasmon resonance, is adopted to reshape the AuNRs into gold nanospheres. Then, the existence of the AuNRs in designated positions of the fabricated 3D microstructures can be achieved. The doped AuNRs with two-photon luminescence also act as contrast agent for internal diagnosis of 3D polymer microstructures.

Nano slit arrays perforated on thin metallic film are the basic structure of metallic nano-optic lenses, which resemble the shape of the conventional glass lens, and can be applied to beam manipulation, such as beam reflecting/deflecting or focusing. It has been proven that optical transmission is feasible through metallic nano slit arrays, making new nano technology applications possible. In conventional dielectric lenses, the edge effect-the very strong diffraction of the transmitted beam that take place at the lens edges restricts the possibility of sizing down the conventional optics components to a sub-wavelength range. This is due to the fact that the size of the lens is an important determinant of focusing beam to the nano scale. In this paper we present the metallic nano lenses and study their optical transmission properties. These lenses do not suffer from the edge effect mentioned above. The phase of each nanoslit element can be managed by changing the material of the metal film and/or the structural parameters of the lens. In our simulation work, we examine the transmission performance of metallic nano slit arrays by the method of finite-difference time-domain (FDTD). We use various metals such as copper, silver, aluminum and titanium as the material of the thin films. We also investigate various structural parameters such as slit number, width and thickness, to show their influence on the optical transmission performance. By adjusting the material and/or structural parameters of the Nano slit arrays, the desired transmission performance can be realized.

We theoretically investigate the effect of fabrication-related disorders on subwavelength metal-dielectric-metal plasmonic waveguides. We use a Monte Carlo method to calculate the roughness-induced excess attenuation coefficient with respect to a smooth waveguide. We find that the excess attenuation is mainly due to reflection from the rough surfaces. For small roughness height (δ<4nm), the excess optical power loss due to disorder is small compared to the material loss in a smooth waveguide. However, for large roughness height (δ>4nm), the excess attenuation increases rapidly and the propagation length of the optical mode is severely affected. We also find that the disorder attenuation due to reflection is maximized when the power spectral density of the disordered surfaces at the Bragg frequency is maximized. Finally, we show that increasing the modal confinement or decreasing the guide wavelength, increase the attenuation due to disorder.

Plamonic coaxial structures have drawn considerable attetion recently because of their unique properties. They exhibit different mechanisms of extraordinary optical transmission observed from subwavelength holes and they can support localized Fabry-Pérot plasmon modes. In this work, we experimentally demonstrate color filters based on coaxial structures fabricated in optically thick metallic films. Using nanogaps with different apertures from 160 nm down to only 40 nm, we show varying color outputs when the annular aperture arrays are illuminated with a broadband light source. Effective color-filter function is demonstrated in the optical regime. Different color outputs are observed and optical spectra are measured. In such structures, it is the propagating mode playing an important role rather than the evanescent. Resonances depend strongly on ring apertures, enabling devices with tunability of output colors using simple geometry control.

The local excitation of the surface plasmon vortex and hot spot via the plasmonic vortex lens is both theoretically studied and experimentally demonstrated. The phase delay of the excited surface plasmon is caused by the three parameters, which are the geometrical topological charge of the plasmonic vortex lens, the polarization state of the incident beam, and the angular momentum state of the incident beam. These parameters eventually decide the total topological charge of the surface plasmon vortex generated at the center of the plasmonic lens structure. From these results, we finally provide the simple relation between these parameters and the state of the surface plasmon vortex generated by plasmonic lens.ïýïý

Planar photonic crystal (PPC) has recently attracted much attention as a promising platform for the realization of compact nanocavity devices. Our proposed photonic crystal (PC) structure consists of a periodic hole array with a point defect at the center. The device has been integrated on the facet of a quantum cascade laser working in the mid-infrared region of optical spectrum. Finite-difference time domain (FDTD) simulations have been performed to optimize the design structure. Simulations showed that with a periodicity of the holes (Λ) between 1.3um and 1.4um, the near field enhancement at the center of the cavity on the same level as the top metal surface can be as high as 10 times the incident electric field. The radius of the hole and center cavity radius are 0.45 and 0.2 times Λ. The structure was simulated at experimentally measured operating wavelength (λ=5.98um) of our device. During fabrication, we used a buffer SiO₂ layer thickness of 100nm followed by metal-dielectric-metal structure with layer thicknesses of Au - SiO₂ -Au (100/20/ 100 nm). Next, the MDM photonic crystal design was fabricated on the MDM coated facet of the QCL using focused ion beam (FIB) milling. The integrated device has been tested using an apertureless mid-infrared near field scanning optical microscopy (a-NSOM). The measurement set-up is based on an inverted microscope coupled with a commercially available Atomic Forced Microscopy (AFM). Using this technique, we could simultaneously measure the topography and NSOM image of the photonic crystal integrated QCL. It showed that the combination of high quality factor and extremely low mode volume of the PC design can squeeze the optical mode within a nanometric spot size ~ 450nm. The experimental results is a proof of concept, although we believe, further optimization and improvisation with different PC designs can lead squeezing the optical mode into a much smaller volume. Such integrated device are capable of focusing radiant infrared light down to nanometer length scale and strongly enhance the near field intensity which can be extremely useful in molecular sensing.

A label free, non-destructive and high sensitivity biosensor with sub-nanometer thickness resolution is presented. We investigate various sequences of DNA attached on gold nanoparticles (AuNPs) on top of a layer of self assembling molecules. A strategy to amplify localized surface plasmon resonance (LSPR) response is made by sandwiching DNA sequences between two AuNPs. We monitor the induced changes in polarization state or phase of reflected light from the surface as a function of the photon energy as a sensor signal by using ellipsometry and compare that with theoretical simulation.

We present here a mathematical formulation determining the enhancement factors of Raman scattered light from molecules adsorbed on to multiply coated ellipsoidal particles. We use this formulation to present enhancement of Raman scattering from molecules, such as pyridine and CV from nanoparticles of gold and silver as well as their core-shell structures with magnetic metal cobalt. The nanoparticles of these metals are widely used in biomedical applications. We also present results for the cases when the nanoparticle is covered with a monolayer of Raman active molecules and dispersed randomly in a medium. Our results can be of importance in medical technology.

We have theoretically investigated the effects of temperature on the superlensing properties of single metal and stacked metal-dielectric films. We find that decreasing the temperature usually has the effect of slightly lowering the optimum operating frequency of the superlens. The imaging performance of various designs are evaluated by analytic calculations and simulations. Accurate modeling of the temperature dependence on the focusing/imaging properties of such structures is important for many potential applications and may in certain suggested cases lead to direct applications as e.g. local temperature sensing.

Structures consisting of layered metallic films can be designed to have evanescent transmission and reflection coefficients that oscillate as a function of transverse wavevector and frequency. When combined with an exit face diffraction grating, a setup can be realized where for different frequencies one has different spatial components of an incident field scattered into the dominant propagating order behind the grating. One is thereby able to simultaneously gather information over a larger range of evanescent field components by combining measurements at more than one frequency. For sources emitting over the relevant frequency ranges, it becomes possible to reconstruct a higher ("super") resolution image in the far-field without the need for mechanical scanning or consecutive measurements. We present calculations and simulations demonstrating the operation of the proposed technique at visible frequencies along with some preliminary experimental results on the transmission properties of the proposed metal/dielectric stacks.

Modifications in scattering strength of and local field enhancement by retardation-based plasmonic nanoantennas when being transformed from straight nanorods to split-rings are investigated. The scattering properties are monitored by linear reflection and extinction spectroscopy whereas local field enhancement is estimated from measurements on individual nanoantennas by nonlinear scanning optical microscopy in which two-photon-excited photoluminescence (TPL) is detected. The linear and nonlinear optical characterizations reveal, that the optical response of nanoantennas is dominated by constructively interfering short-range surface plasmon polaritons (SR-SPP) and that the transformation of straight nanorods into split-rings by bending significantly influences the scattering strength. Importantly, strong suppression of scattering for the fundamental SR-SPP mode is observed when the bend radius is decreased, a feature that we attribute to the decrease in the nanoantenna electric-dipole response in tact with its bending. The experimental observations are corroborated with numerical simulations using the finite-element method.

Finite difference time domain (FDTD) simulations are used to find the electric field intensity at the center of a cluster of plasmonic nanoparticles irradiated by a planewave source. We use an iterative optimization algorithm to maximize the electric field intensity. The resulting optimized configurations are found to be non-symmetric and non-intuitive, and cannot be obtained by analytical calculation methods. Experimentally, we investigate a novel technique using angle evaporation to produce plasmonic nanostructures with gap sizes of 1-2 nm. We evaluate the plasmonic activity of these nanoparticles both experimentally using surface enhanced Raman spectroscopy (SERS) measurements and theoretically using FDTD simulations. These simulations predict an electric field intensity enhancement of 82,400 at the center of the nanoparticle dimer, and an electromagnetic SERS enhancement factor of 10⁹-10¹⁰.

State-of-the-art copper interconnects suffer from increasing spatial power dissipation due to chip downscaling and RC delays reducing operation bandwidth. Wide bandwidth, minimized Ohmic loss, deep sub-wavelength confinement and high integration density are key features that make metal-insulator-metal waveguides (MIM) utilizing plasmonic modes attractive for applications in on-chip optical signal processing. Size-mismatch between two fundamental components (micron-size fibers and a few hundred nanometers wide waveguides) demands compact coupling methods for implementation of large scale on-chip optoelectronic device integration. Existing solutions use waveguide tapering, which requires more than 4λ-long taper distances. We demonstrate that nanoantennas can be integrated with MIM for enhancing coupling into MIM plasmonic modes. Two-dimensional finite-difference time domain simulations of antennawaveguide structures for TE and TM incident plane waves ranging from λ = 1300 to 1600 nm were done. The same MIM (100-nm-wide Ag/100-nm-wide SiO₂/100-nm-wide Ag) was used for each case, while antenna dimensions were systematically varied. For nanoantennas disconnected from the MIM; field is strongly confined inside MIM-antenna gap region due to Fabry-Perot resonances. Major fraction of incident energy was not transferred into plasmonic modes. When the nanoantennas are connected to the MIM, stronger coupling is observed and E-field intensity at outer end of core is enhanced more than 70 times.