This PDF file contains the front matter associated with SPIE Proceedings Volume 9921, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

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Nonlinear phenomena provide novel light manipulation capabilities and innovative applications. Recently, we discovered nonlinear saturation on single-particle scattering of gold nanospheres by continuous-wave laser excitation and innovatively applied to improve microscopic resolution down to λ/8. However, the nonlinearity was limited to the green-orange plasmonic band of gold nanosphere, and the underlying mechanism has not yet been fully understood. In this work, we demonstrated that nonlinear scattering exists for various material/geometry combinations, thus expanding the applicable wavelength range. For near-infrared, gold nanorod is used, while for blue-violet, silver nanospheres are adopted. In terms of mechanism, the nonlinearity may originate from interband/intraband absorption, hot electron, or hot lattice, which are spectrally mixed in the case of gold nanosphere. For gold nanorod and silver nanosphere, nonlinear scattering occurs at plasmonic resonances, which are spectrally far from interband/intraband absorptions, so they are excluded. We found that the nonlinear index is much larger than possible contributions from hot electrons in literature. Therefore, we conclude that hot lattice is the major mechanism. In addition, we propose that similar to z-scan, which is the standard method to characterize nonlinearity of a thin sample, laser scanning microscopy should be adopted as the standard method to characterize nonlinearity from a nanostructure. Our work not only provides the physical mechanism of the nonlinear scattering, but also paves the way toward multi-color superresolution imaging based on non-bleaching plasmonic scattering.

An exact calculation of the local electric field E(r) is described for the case of an external current or plane wave source in a setup of an E₁, μ₁ slab in an E₂, μ₂ medium. For this purpose we first calculate all the general eigenstates of the full Maxwell equations. These eigenstates are then used to develop an exact expansion for the physical values of E(r) in the system characterized by physical values of E₁, E₂, μ₁, and μ₂. Results are compared with those of a previous calculation of the local field where μ = 1 everywhere. Numerical results are shown for the eigenvalues in practically important configurations where attaining an optical image with sub-wavelength resolution has practical significance. We show that the k ≫ k₂ components are enhanced for the TM field when E₁/E₂ = −1 and for the TE field when μ₁/μ₂ = −1 where the enhancement of the evanescent waves starts from lower k values as we approach a setup with both E₁/E₂ = −1 and μ₁/μ₂ = −1. We also show that the eigenfunctions for the setup where μ = 1 everywhere correspond to configurations of 3D phased arrays.

In this work, we report on fabrication of deep-profile one- and two-dimensional lattices made from Al-doped ZnO (AZO). AZO is considered as an alternative plasmonic material having the real part of the permittivity negative in the near infrared range. The exact position of the plasma frequency of AZO is doping concentration dependent, allowing for tuning possibilities. In addition, the thickness of the AZO film also affects its material properties. Physical vapor deposition techniques typically applied for AZO coating do not enable deep profiling of a plasmonic structure. Using the atomic layer deposition technique, a highly conformal deposition method, allows us to fabricate high-aspect ratio structures such as one-dimensional lattices with a period of 400 nm and size of the lamina of 200 nm in width and 3 μm in depth. Thus, our structures have an aspect ratio of 1:15 and are homogeneous on areas of 2×2 cm² and more. We also produce two-dimensional arrays of circular nanopillars with similar dimensions. Instead of nanopillars hollow tubes with a wall thickness on demand from 20 nm up to a complete fill can be fabricated.

During the last decade, important attention has been devoted to the observation of nonlinear optical processes in plasmonic nanosystems, giving rise to a new field of research called nonlinear plasmonics. The cornerstone of nonlinear plasmonics is the use of the large field enhancement associated with the excitation of localized surface plasmon resonances to reach high nonlinear conversion yields. Among all the nonlinear optical processes, second harmonic generation (SHG), the process whereby two photons at the fundamental frequency are converted into one photon at the second harmonic frequency, is undoubtedly the most studied one due to the relative simplicity of its experimental observation. However, the physical origin of SHG from plasmonic nanostructures hides a lot of subtleties, which are mainly related to its particular behavior upon inversion symmetry. In order to catch all the peculiarities of SHG, it is mandatory to develop dedicated numerical methods able to accurately describe all the underlying physical processes and the influence of the initial assumptions needs to be well-characterized. In this presentation, we discuss and compare different methods (namely full-wave computations based on the surface integral equations method, mode analysis, the Miller’s rule, and the effective nonlinear susceptibility method) proposed for the evaluation of the SHG from plasmonic nanoparticles emphasizing their limitations and advantages. In particular, the design of double resonant antennas for efficient nonlinear conversion at the nanoscale is addressed in detail.

Although gold nanoparticles (GNPs) are promising probes for biological imaging because of their attracting optical properties and bio-friendly nature, properties of the multi-photon (MP) emission from GNP aggregates produced by a short-wave infrared (SWIR) laser have not been examined. In this paper, characterization of MP emission from aggregated 50 nm GNPs excited by a femtosecond (fs) laser at 1560 nm is discussed with respect to aggregate structures. The key technique in this work is single particle spectroscopy. A pattern matching technique is applied to correlate MP emission and SEM images, which includes an optimization processes to maximize cross correlation coefficients between a binary microscope image and a binary SEM image with respect to xy displacement, image rotation angle, and image magnification. Once optimization is completed, emission spots are matched to the SEM image, which clarifies GNP ordering and emission properties of each aggregate. Correlation results showed that GNP aggregates have stronger MP emission than single GNPs. By combining the pattern matching technique with spectroscopy, MP emission spectrum is characterized for each GNP aggregate. A broad spectrum in the visible region and near infrared (NIR) region is obtained from GNP dimers, unlike previously reported surface plasmon enhanced emission spectrum.

A two-photon photoemission microscopy experiment with femtosecond time-resolution for imaging of propagating surface plasmon polaritons is discussed. The experimental setup of an actively Pancharatnam’s phase stabilized interferometer is described, and a temporal stability in time-resolved two-photon photoemission microscopy of less than 20 attoseconds is demonstrated. The time-resolved setup is applied to investigate the interaction of a surface plasmon polariton wave packet with a plasmonic beam-splitter. Pump-probe data recorded at times before and after the interaction of the surface plasmon polariton wave packet with the beam-splitter indicate transmission and reflection coefficients of T≈0.3 and R≈0.4, respectively.

We have realized a plasmonic sensor based on Au/Pd metal bilayer in a multimode plastic optical fiber. This metal bilayer, based on a metal with high imaginary part of the refractive index and gold, shows interesting properties in terms of sensitivity and performances, in different refractive index ranges. The development of highly sensitive platforms for high refractive index detection (higher than 1.38) is interesting for chemical applications based on molecularly imprinted polymer as receptors, while the aqueous medium is the refractive index range of biosensors based on bio–receptors. In this work we have presented an Au/Pd metal bilayer optimized for 1.38-1.42 refractive index range.

We present second-order nonlinear optical properties of two-dimensional periodic arrays of Au nanorods arranged two dimensionally on SiO2 along with the one-dimensional periodic arrays in the direction either coaxial or vertical to the plasmon polarizations. The geometry of the nanorods was symmetric with respect to the normal line to the top surface of the rods, and the system was excited at oblique incidence angles so as to break the centro-symmetry. Our experimental results demonstrated that the coordination longitudinal to plasmon polarizations reduced the nonlinearities of the nanorods while the coordination transverse to polarizations did not give any significant influences on them.

All-optical modulation of light using metallic nanostructures can potentially enable processing of information with speed in the terahertz range. This is because the optical nonlinearity of metals dictated by the electron-phonon coupling is intrinsically fast. Nobel metals have achieved great success to this end due to their superior plasmonic properties in the visible. However, each type of noble metals only works in a specific wavelength range and therefore broadband spectral response covering the wide visible spectrum can be a challenge. Here we introduce indium-tin-oxide nanorod arrays (ITO-NRAs) which exhibit broadband response covering the visible spectrum. We show that the static spectral response of ITO-NRAs does not depend on the incident polarization and is insensitive to whether the lattice is a square or a rectangle. We further demonstrate that the transmission spectrum can be slightly shifted by changing the sample temperature, as well as adjusting the doping concentration which can be achieved by annealing the sample in oxygen rich environments. When pumped by an optical pulse with photon energy above the bandgap, the transmission can be modified in the entire visible range. These preliminary results show that ITONRAs offer unique opportunities for all-optical modulation in optical frequencies.

Heat-assisted magnetic recording (HAMR) is a potential enabling technology for ultrahigh density data storage systems. In HAMR, a near-field transducer (NFT) delivers a subdiffraction heat spot to record bits of data on a high-anisotropy magnetic media. We developed an intuitive 1D Fourier model that expedites the analysis and design of the NFT. Among other strengths, the simple model predicts rather surprisingly and in agreement with 3D simulations, that for metallic nanoresonators the longitudinal component of the electric field dominates the heat transfer to the media. The proposed Fourier model serves well as a platform to study electromagnetic behavior such as field confinement and heat spot generation of 3D NFT designs.

Is it possible to design a dedicated nanostructure on which all surface features contribute entirely to energy harvesting within a solar cell? This is an important challenge in the light that the efficiency of the solar cell technology utilised has a direct impact on the required land-use and also on reaching grid parity. Here, we take a unique approach and present an analytically derived optimum solution to the problem: a nanoscale metal topography, capable of significantly improving the efficiency of solid state solar cells via excitation of surface plasmon polaritons (SPPs). The presented structure is designed to achieve broadband excitation of SPPs through the highest possible density of desired k-vectors at the interface. This leads to high weighted absorption enhancements (>130%) and unprecedented improvements (>30%) of solar cell external quantum efficiencies over the entire harvestable range.

Observing the resonance wavelengths of nanoantennas (NAs) with changing incident angles in TM and TE polarization. Extinction cross section shows the dark and bright coupling modes at resonance wavelength of NAs with symmetry breaking oblique incidence. The plasmonic enhancement is stronger under evanescent wave in total internal reflection.

We have numerically evaluated the complex valued eigenfrequencies of infinite silver nanotubes as a function of the ratio of internal and external radius, by solving the surface plasmon dispersion relations for the TE polarization. The results are shown for tubes of external radius of 20 nm, 50 nm, 100 nm, 150 nm, 200 nm and 300 nm with the internal radius varying from 0.1 to 0.9 fractions of the external radius. We have observed that their quality factor Q is substantially enhanced as compared to solid cylinders or wires.

Surface-enhanced Raman scattering (SERS) is drawing increasing interest in fields such as chemical and biomolecular sensing, nanoscale plasmonic engineering and surface science. In addition to the electromagnetic and chemical enhancements in SERS, several studies have reported a “back-side” enhancement when nanostructures are excited through a transparent base rather than directly through air. This additional enhancement has been attributed to a local increase in the electric field for propagation from high to low refractive index media. In this study, Mueller matrix ellipsometry was used to derive the effective optical constants of Ag nanostructures fabricated by thermal evaporation at oblique angles. The results confirm that the effective optical constants of the nanostructured Ag film depart substantially from the bulk properties. Detailed analysis suggests that the optical constants of the nano-island Ag structures exhibit uniaxial optical properties with the optical axis inclined from the substrate normal towards the deposition direction of the vapour flux. The substrates were functionalized with thiophenol and used to measure the wavelength dependence of the additional SERS signal. Further, a model based on the Fresnel equations was developed, using the Ag film optical constants and thickness as determined by ellipsometry. Both experimental data and the model show a significant additional enhancement in the back-side SERS, blue shifted from the plasmon resonance of the nanostructures. This information will be useful for a range of applications where it is necessary to understand the effective optical behaviour of thin films and in designing miniaturized optical fibre sensors for remote sensing applications.

Surface Plasmon Resonance (SPR) optical fiber sensors can be used as cost-effective small sized biosensors that are relatively simple to operate. Additionally, these instruments are label-free, hence rendering them highly sensitive to biological measurements. In this study, a three-channel microstructure optical fiber plasmonic-based portable biosensor is designed and analyzed using Finite Element Method. The proposed system is capable of determining changes in sample’s refractive index with precision of order one thousandth. The biosensor measures three absorption resonance wavelengths of the analytes simultaneously. This property is one of the main advantages of the proposed biosensor since it reduces the error in the measured wavelength and enhances the accuracy of the results up to 10^-5 m/RIU by reducing noise. In this paper, Jurkat cell, an indicator cell for leukemia cancer, is considered as the analyte; and its absorption resonance wavelengths as well as sensitivity in each channel are determined.

Over the last decade, plasmonic photothermal therapy (PPTT) has received significant attention as the new therapeutic strategy for the cancer therapy due to unique characteristics of the gold-nanoparticles. The characterization of the spatiotemporal heating potential for the gold nanorods (GNR) through mimicking PPTT process on the various conditions can help more quantitative approaches to treatment planning. The purpose of this study was to clearly understand the optical-thermal interactions between the laser, GNRs, and bio-tissues, and provide the information in clinical applications to implement the concept of heterogeneity, which can enable the optimization of treatment parameters for superficial breast cancer treatment.

Surface plasmons are known for their ability to provide large field enhancement at the interface between a metal and another medium. They can be observed in a variety of structures ranging from plain metallic films to nanoparticles and gratings. Thanks to their large electric field enhancement, surface plasmons have also been exploited for the enhancement of second and third harmonic generation. In fact, metals possess a relatively high third order susceptibility and, although dipole-allowed quadratic nonlinearities are not present in the bulk, they also display an effective second order response that arises from symmetry breaking at the surface, magnetic dipoles (Lorentz force), inner-core electrons, convective nonlinear sources, and electron gas pressure. While much attention has been devoted to achieve efficient excitation of surface plasmons to improve far-field harmonic generation, little or no attention has been paid to the dissipation of the generated harmonic light. Therefore, we undertake a discussion of both harmonic generation and absorption in simple metallic/dielectric interfaces with or without excitation of surface plasmons. We demonstrate that, despite the best efforts embarked upon to study plasmon excitation, the absorbed harmonic energy can far surpass the energy emitted in the far-field. These findings suggest that quantification of the absorbed harmonic light should be an important parameter in evaluating designs of plasmonic nanostructures for frequency mixing.

The interaction between plasmonic resonances, sharp modes, and light in nanoscale plasmonic systems often leads to Fano interference effects. This occurs because the plasmonic excitations are usually spectrally broad and the characteristic narrow asymmetric Fano line-shape results upon interaction with spectrally sharper modes. We investigate a plasmonic waveguide system using the finite-difference time-domain (FDTD) method, which consists of a metal-insulator-metal waveguide coupled with a rectangle and a ring cavity. Numerical simulations results show that the sharp and asymmetric Fano-line shapes can be created in the waveguide. Fano resonance strongly depends on the structural parameters. This has important applications in highly sensitive and multiparameter sensing in the complicated environments.

Because of the electromagnetic field enhancement effect in subwavelength scale, the surface plasmon wave (SPW) has been widely used in beam forming, bio-prospecting, and subwavelength structure design. But most research work is in the visible light or terahertz frequency band, and the surface plasmonic material (SPM) is usually limited to metals. In the microwave band, complex structures have to be used to achieve the desired subwavelength effects, making use of both metal and dielectric materials. In this paper, we propose the excitation of SPW in the microwave range using a simple structure and the material of indium tin oxide (ITO). By measuring the electric field profile during the propagation process, the excitation of SPW in ITO was verified. At the same time, frequency dependence was seen during the propagation process. Therefore, ITO can be a good SPM in the microwave band, just like metals in the visible light band. Considering the transparent characteristics of ITO, it can have many interesting applications.

In this work, we have studied the effect of AuGe alloy nanoparticles deposition on properties of molecular beam epitaxy grown heptalayer coupled InGaAs 5.25 mono-layer quantum-dots (QDs) samples. AuGe 12 nm film was deposited using electron beam evaporator on these samples which were later annealed at 300 °C to create AuGe nanoparticles. SEM measurement confirms formation of AuGe nanoparticles which support surface Plasmon modes. The PL spectra at 20K confirms maximum enhancement of 53% in intensity of peak at ̴̴ 1123 nm for 300 °C annealed sample in comparison to as-grown (without nanoparticle) sample. Single pixel detectors were fabricated from asgrown and 300°C annealed nanoparticle sample using two level lithography and wet etching process. We have observed two-order and one-order augmentation in responsivity and detectivity from device having nanoparticles compared to the as-grown respectively at 80K. Peak detectivity of 4.2×10⁷cm.Hz ^1/2/W at 80K was observed for device having nanoparticles. Around 30% increment in spectral response having peak around 5μm at -1V bias for device having AuGe nanoparticles compared to the as-grown device was observed. The observed enhancement is due to increase light trapping or light scattering into the device by nanoparticles. Demonstration of this plasmonic-based detector will move forward the development of high-performance infrared QDs detectors.

The optical fiber sensor for higher pressure detection based on surface-plasmon resonance (SPR) phenomena is design and analysed. The optical fiber is coated with a thin film of metal by removing cladding from core of a multi-mode optical fiber. The calculated pressure sensitivity is based on two parameter. First one is the derivative of the resonance wavelength of SPR-based optical sensor with respect to the refractive index of surrounding medium; the second is the derivative of refractive index of polymer with respect to the pressure. The proposed structure can be suitable for high sensitivity pressure measurements, for various industrial applications.

We present a strategy to control Fano resonances in hybrid graphene-silicon-on-insulator gratings. The presence of a mono- or few-layer graphene film allows to electrically and/or chemically tuning the Fano resonances that result from the interaction of narrow-band, quasi-normal modes and broad-band, Fabry-Perot-like modes. Transmission, reflection and absorption spectra undergo significant modulations under the application of a static voltage to the graphene film. In particular, for low values of the graphene chemical potential, the structure exhibits a symmetric Lorentzian resonance; when the chemical potential increases beyond a specific threshold, the grating resonance becomes Fano-like, hence narrower and asymmetric. This transition occurs when the graphene optical response changes from that of a lossy dielectric medium into that of a low-loss metal. Further increasing the chemical potential allows to blue-shift the Fano resonance, leaving its shape and linewidth virtually unaltered. We provide a thorough description of the underlying physics by resorting to the quasi-normal mode description of the resonant grating and retrieve perturbative expressions for the characteristic wavelength and linewidth of the resonance. The roles of number of graphene layers, waveguide-film thickness and graphene quality on the tuning abilities of the grating will be discussed. Although developed for infrared telecom wavelengths and silicon-on-insulator technology, the proposed structure can be easily designed for other wavelengths, including visible, far-infrared and terahertz, and other photonic platforms.

Extraordinary optical transmission (EOT) is a classic phenomenon in plasmonics. The study of plasmonic nanostructures in the ultraviolet (UV) is a relatively uncharted field due to challenges in both engineering (nanostructure design, optimization, and fabrication) and materials science (detailed composition analysis). Our previous research has been mainly focused on UV field enhancement ofdifferent Al nanostructures. In this work, two-dimensional periodic nanohole arrays in Aluminium (Al) and Magnesium (Mg) films were fabricated using Ga focused ion beam (FIB) lithography. Optical transmission through the arrays was obtained in the UV and visible range, with varying array periodicity. Transmission results showed strong resonance enhancement in the UV and visible region resulting from SPP coupling, with corresponding red-shift as the period increases, while waveguide mode peaks remain in place. Comparing Al and Mg EOT results, Al hole-array enabled larger transmission than that of Mg. Dips in transmission through Al arrays occur at similar spectral positions to those of Mg arrays with same periods. Numerical analysis was carried out through finite-difference-time-domain (FDTD) method, which showed far-field transmission consistent with experiments in general. The model was constructed based on transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) of cross-sectioned samples. The effect of Gallium (Ga) implantation from FIB fabrication was qualitatively studied, which indicated Ga implants inside the hole bottom as well as higher implantation within Mg than that within Al. The model also takes into account sidewall geometry and undercut into the substrate.

Ag and Cu nanoparticles supported in mordenite structure have been formed applying reduction temperatures in the range 100-400 C and varying Ag/Cu atomic ratios. Absorbance spectra of samples exhibit signature features consistent with absorption via localized surface plasmons propagating in metallic nanoparticles. The formation of binary Ag-Cu nanoparticles is inferred. Theoretical calculations within an average field Maxwell-Garnett model modified for a three component composite system are used to interpret resonance shifts and relative intensities of plasmon peaks in the experimental findings. Within the applied model the relative volume occupied by each metallic species can be changed. This permits the simulation of experimental conditions of the samples. It is experimentally found that the simultaneous presence of two metal species during the synthesis affects reduction temperatures, stability and relative concentration of embedded nanoparticles. Furthermore the observed optical spectra of the supported bimetallic nanoparticles is contrasted with that of single metal nanoparticles studied previously. Our study represents a contribution to the possibility of optical monitoring of synthetic pathways in zeolite + metal nanoparticle systems.

We analyze the resonant interaction between cumulus of nano-particles distributed on a two-dimensional array controlling the polarization states on the illumination, this allows controlling the dipole moment induced in a tunable-way obtaining an analytic expression for the refractive index. The resonant effects depend on the parameters that characterize the spatial distribution of the particle arrangement. We present two cases, firstly the interaction is described using a linear polarization on a linear particle array, and secondly it is obtained using circular polarization inducing resonant interaction between ring-particle kind structures. The refractive index associated to both configurations is implemented in the Fresnel equations for the study of the reflectivity and transmittance of optical fields. As a main result of the analysis is that we can to identify and control the parameters required for the synthesis of metamaterials. Computer simulations are presented.

In this work, we report the experimental and numerical study of second harmonic generation (SHG) from Si-surface with randomly distributed Au-nanorods. The dependence of plasmonic resonance frequency was studied numerically for the gold nanorod-silicon dioxide-silicon substrate system as a function of nanorod sizes and dioxide film thickness. The numerical results demonstrate a high sensitivity of plasmonic resonance on the silicon dioxide thickness at the range up to 6 nm. We measured experimentally the dependencies of second harmonic signal as functions of the polarization angle of the pump beam from randomly distributed Au-nanorods on the Si-surface.

Many of today’s technological applications, such as solar cells, light-emitting diodes, displays, and touch screens, require materials that are simultaneously optically transparent and electrically conducting. Here we explore transparent conductors based on the excitation of surface plasmons in nanostructured metal films. We measure both the optical and electrical properties of films perforated with nanometer-scale features and optimize the design parameters in order to maximize optical transmission without sacrificing electrical conductivity. We demonstrate that plasmonic transparent conductors can out-perform indium tin oxide in terms of both their transparency and their conductivity.

An optical setup able to switch between the surface-plasmon resonance (SPR) angular resolved spectroscopy in Kretschmann’s configuration and SPR imaging is presented. The system’s concept is based on an adaptive optical module which allows to perform the two complementary measurements by sharing all optical elements and avoiding any moving part. Among the main advantages given by this switching feature there are both the fast calibration capability of the SPR image by using the angular resolved spectroscopy and the optimization of the SPR chip probing area.

The phase function of optical fields collapse on focusing regions generating a discontinuity in the amplitude function, this induces sources or sinks that corresponds with the topological charge. When the previous comments are transferred to the Plasmon optics context, the discontinuity of the electromagnetic field generates a real distribution of electric charge. This distribution has associated a geometry which can be obtained from the boundary condition of the field. A dynamical character can be implemented on the charge distribution using partial coherence processes in the illumination configuration for the synthesis of the Plasmon field, generating local current distributions modifying selectively the electromagnetic field properties. The model is performed using as a prototype the interaction between plasmon fields Pearcey and Airy kind. Both of them have associated a catastrophe function to the phase function, this mathematical representation allows us to identify and quantify the discontinuity of the electromagnetic field. The computational simulations show that the charge/current distributions present non-linear effects, which offers applications for tunable spectroscopy, plasmonic tweezers, etc.