This PDF file contains the front matter associated with SPIE Proceedings Volume 7395, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

We demonstrate nanofabrication of photoreactive azobenzene molecular thin films using optical migration of molecules induced by local polarization in optical near-fields. Transportation and alignment control of the nanomaterial systems were investigated to modulate the excitation of the optical near-fields. Energy transfers from fluorescent molecules were observed along a planar boundary system of metals and dielectrics. The fundamental processes of tunneling energy that flowed to the metallic layer were evaluated from the angular distribution of scattered light in a far field, corresponding to the angular spectrum of scattered fields, including those of evanescent waves excited near the fluorescent molecules and nanostructures fabricated on azo molecular films.

This letter provides a brief summary on early work and developments on both controlling and studying the optical properties of resonant metal nanoparticles and reports on all progress achieved since two years. Our approach is based on controlled nanoscale photopolymerization triggered by local enhanced electromagnetic fields of silver nanoparticles excited close to their dipolar plasmon resonance. By anisotropic polymerization, symmetry of the refractive index of the surrounding medium was broken: C1v symmetry turned to C2v symmetry. This approach has overcome all the difficulties faced by scanning probe methodologies to reproduce the form of the near field of the localized surface plasmons and provides a new way to quantify its magnitude. Furthermore, this approach leads to the production of polymer/metal hybrid nano-systems of new optical properties.

We propose a method for the fabrication of self-assembled semiconductor quantum dots (QDs) and the control of their density and emission wavelength. This method would be fundamental toward the fabrication of nanophotonic devices. We used molecular beam epitaxy and fabricated self-assembled QDs from various materials under various growth conditions. We controlled the emission wavelength over a wide range (700-1700 nm) by changing the materials around the QDs. We used antimonide-related materials or a highly stacked structure to control the density of the obtained QDs within the range of 10⁸-10¹³/cm².

Surface plasmon polariton enhanced fluorescence from CdSe/ZnS quantum dots (QD) deposited onto patterned gold/PMMA substrates has been observed. Comparison of gold, chromium, and ITO substrates is used to verify restriction of enhancement effect to surface plasmon polariton supporting materials. Enhanced fluorescence is observed by using one dimensional gratings defined by electron beam lithography to provide phase matched coupling into surface plasmon polaritons on the metal film surface. Controlled variation of grating parameters is used to examine the dependence of this effect on the periodicity and shape of the coupling grating. Analysis of the results indicates that strong enhancement requires optimization of both grating periodicity and structure for specific wavelengths and materials.

The poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) organic films are widely employed as electronic donor and acceptor in the field of organic film solar cell because of their high photovoltaic conversion efficiency. A home-built parabolic mirror assisted confocal and apertureless near-field optical microscope was used to investigate the degradation behavior of the film and to distinguish the donor and acceptor domains both topographically and optically. Under ambient condition, the degradation rates are decreased in the sequence of pristine P3HT, blend P3HT:PCBM film and pristine PCBM. N2 protection dramatically slows down the film degradation rate. Using confocal spectroscopic mapping, we are able to distinguish the local distributions of P3HT and PCBM. Micrometer PCBM aggregates were observed due to the thermal annealing process. Our experimental methods show the possibility to investigate morphology and the photochemistry properties of the organic solar cell films with high spatial resolution.

Nanoscale materials absorb, propagate, and dissipate energy very differently than their bulk counterparts. Furthermore, hybrid nanostructures consisting of molecular and plasmonic materials with strongly coupled electronic states can produce new optical states and decay pathways that provide additional handles with which to externally control energy flow in complex nanostructured systems. In this talk, we discuss our recent studies of electromagnetic coupling and associated temporal dynamics of molecular excitations with plasmonic resonances supported by either localized or extended planar geometries. Recent experimental results and theoretical analysis for observing and controlling coherences between molecular excitations and plasmonic polarizations are shown. Advances will explore new directions in ultrafast manipulation of energy dissipation processes in hybrid plasmonic structures, as well as ultrafast addressing and switching in plasmonics-based circuit architectures. Also discussed are recent synthetic advances in the creation of hybrid materials. Ultimately, these studies may impact a range of next-generation optical materials and devices, of relevance to new energy conversion materials, nanoscale photocatalysis, or plasmon-enhanced sensors.

Shape dependent sensitivity of localized surface plasmon based biosensing was investigated by combining single particle protein sensing and multiple multipole program simulation. Significantly higher sensitivity was observed for tetrahedral particles than spherical ones, which was revealed by careful structural analysis of individually measured particles. The simulation of the corresponding particles with layered protein adsorption model showed consistent optical property and sensitivity, which were explained in terms of the field enhancement at the pointing edges.

The plasmon resonance of noble metal nanoparticles (NP) manifests itself in a variety of extraordinary optical properties. Resonant excitation of the conduction electrons by incident radiation generates a localized surface plasmon resonance (LSPR) that is responsible for a variety of surface enhanced optical phenomena. This unique optical property coupled with well-established surface chemistry allows us to utilize both Ag and Au NP as optical contrasting agents to probe and monitor the surface receptors of cells. We have employed two plasmon-assisted optical techniques (namely, surface enhanced Raman scattering, and resonant Rayleigh scattering) to monitor the adrenergic receptors in mammalian cardiomyocyte cells that have been labeled with functionalized Ag NPs. In this study, a unique Raman reporter molecule, 4-(mercaptomethyl)benzonitrile, was developed to provide an easily identifiable vibration, the C≡N stretch, in a spectral window free from Raman bands of cell constituents and other biomolecules used in receptor crosslinking and surface passivation. Successfully labeled cells were then monitored with both optical techniques. Both techniques are related through the plasmonic properties of the noble metal NP and combined with high resolution imaging techniques; we outline the importance that different NP architectures play in the different imaging techniques. Furthermore, we will discuss the instrumentation and plasmonic implications in the design of NP best suited for such multimodal imaging approaches.

Surface plasmon resonances in metal nanostructures can lead to novel optical properties. The greatly enhanced electromagnetic field makes surface-enhanced Raman scattering (SERS) a highly sensitive spectroscopic technique. We employed Ag nanowires as plasmonic waveguide and achieved remote-excitation SERS at a few molecules level. The junctions between metal nanowires and nanoparticles offer hot spots for SERS, while the enhancement strongly depends on the laser polarization. We studied the polarization dependence in Au nanowire-nanoparticle systems of different geometry. The polarization of Raman-scattered light in SERS is a rarely studied topic. We found nanoantennas composed of a few nanoparticles can manipulate the polarization of emission light. A nanoparticle trimer is the simplest nanoantenna to realize the polarization control. By tuning the position and size of the third particle, emission polarization can be modified in a controllable way. In addition, the refractivity of the surrounding media also plays a crucial role for the emission polarization.

We have performed the three dimensional (3D) numerical analysis for a gap plasmon waveguide with two stubs in a silver film by using the 3D finite-difference time-domain (FDTD) method. The simulated transmittance shows that such the 3D structure works as a wavelength selective device with submicron size as already predicted in the 2D simulations. We have also fabricated such a structure on a glass substrate by using the focused ion beam method. The width of the gap is around 150 nm. The observed transmittance spectra of the structure have clearly indicated the wavelength dependence and agree well with those obtained by a numerical simulation. Our results show that the structure proposed by us is promising for a compact wavelength selective device.

We present a rigorous closed-form solution to complete the fundamental theory on the transient surface plasmons polaritons (SPP) present on a metal interface, in addition to the conventional long-range SPP, launched by scattering of a metal subwavelength slit. We demonstrate that the Maxwell equations solution includes a transit SPP with complexvalued Exponential Integral envelope by computing the Sommerfeld branch-cut integrals. Physically, the transient SPP is the cylindrical wave initially radiated from the source line, which losses its energy to pumping the long-range SPP mode in the propagation. Its varying damping rate is comparable with existing numerical and approximate results.

The paper studies the molecular-level active control of localized surface plasmon resonances (LSPRs) of Au nanodisk arrays with molecular machines. Two types of molecular machines - azobenzene and rotaxane - have been demonstrated to enable the reversible tuning of the LSPRs via the controlled mechanical movements. Azobenzene molecules have the property of trans-cis photoisomerization and enable the photo-induced nematic (N)-isotropic (I) phase transition of the liquid crystals (LCs) that contain the molecules as dopant. The phase transition of the azobenzene-doped LCs causes the refractive-index difference of the LCs, resulting in the reversible peak shift of the LSPRs of the embedded Au nanodisks due to the sensitivity of the LSPRs to the disks' surroundings' refractive index. Au nanodisk array, coated with rotaxanes, switches its LSPRs reversibly when it is exposed to chemical oxidants and reductants alternatively. The correlation between the peak shift of the LSPRs and the chemically driven mechanical movement of rotaxanes is supported by control experiments and a time-dependent density functional theory (TDDFT)-based, microscopic model.

This paper discusses two aspects of current interest in surface plasmon photonics: the surface sensitivity of surface plasmon waveguides, and the amplification of surface plasmon-polaritons via propagation through an optically pumped dipolar gain medium incorporated into one of the claddings. Physically realisable structures are considered in both cases.

The feasibilities and specific features of coherent nonlinear-optical energy transfer from control fields to a negativephase signal are studied, and they are found to stem from the backwardness of electromagnetic waves inherent to negative-index metamaterials. Plasmonic metamaterials that possess negative group velocity for light waves promise a revolutionary breakthrough in nanophotonics. However, strong absorption inherent to such metaldielectric nanocomposites imposes severe limitations on the majority of such applications. Herein we show the feasibility and discuss different nonlinear-optical techniques of compensating such losses, producing transparency, amplification and even generation of negative-phase light waves in originally strongly absorbing microscopic samples of plasmonic metal-dielectric nanostructured composites.

We investigate the interaction of focused Gaussian and radially-polarized beams with a silver nanosphere, with emphasis on the coupling to localized surface plasmon-polaritons. We discuss the overall efficiency, including the effect of the entrance pupil and of absorption in the nanosphere, showing that a Gaussian beam performs better than a radially-polarized beam, when focused by an aplanatic system. We find that more than 50% of the photons in the incident beam can be reflected using realistic focusing parameters.

Computational studies on the optical properties of nanorods with unique compositions and exotic surface structure are presented. The distinctive architectures investigated-and compared to smooth Au rods-include Ni/Au multiblock rods and nanoporous Au rods. The surface plasmon resonances are extremely dependent upon the morphology and makeup of the nanorods. For a rod with a given aspect ratio, the resonance structure is sensitive to attributes such as the size of Ni sections of multiblock rods and pore structure of nanoporous rods. These studies indicate that control of the optical properties of nanorods is possible via characteristics other than the aspect ratio and suggest that a broader range of tunability is attainable.

Recent developments in nanofabrication and optical near-field metrology have faced complementary modeling techniques with new demands. We present a surface integral formulation that accurately describes the extreme near-field of a plasmonic nanoparticle in addition to its far-field properties. Flexible surface meshing gives precise control over even complex geometries allowing investigation of the effects of fabrication accuracy and material homogeneity on a particle's optical response. Using this technique, the influence of a particle's symmetry and shape on surrounding "hot spots" of extremely large field enhancement is explored, giving insight into the mechanisms of surface enhanced Raman scattering and single-molecule detection techniques.

The optical signature of Au nanoparticles within an yttria-stabilized zirconia matrix has been demonstrated as an optical beacon for changes in emission gas concentrations within harsh environments. It has been proposed that this broadening in the localized surface plasmon resonance (LSPR) band is due to the inelastic scattering of plasmons by filled oxygen ion vacancies. Using the theoretical expressions developed by others for adsorbate induced dampening, a model has been developed for plasmonic nanocomposites to describe the changes observed in the LSPR band broadening for metallic nanoparticles due to the same scattering mechanisms. The model agrees with the broadening observed for the experimental results.

When a linearly polarized light wave propagates in a chiral medium, the polarization plane azimuth rotates clockwise or counter-clockwise depending on the handedness of the material. This effect is called optical activity. It can be observed in a number of crystals and organic liquids, however the rotatory power of chiral materials available in nature is useally very small. That is why chiral planar micro- or nano-structures, which possess a much stronger rotatory power than natural chrial media, have attracted a considerable attention in recent years. We demonstrate large optical activity of chiral subwavelength gratings having no in-plane mirror symmetry and fabricated with metal thin films. For zeroth-order transmitted light, the chirality of these gratings manifests itself in the non-coplanarity of the electric field vectors at the air- and substrate-sides of the metal layer and can be interpreted in terms of the surface pllasmon enhanced non-local light-matter interaction. We demonstrate also that in all-dielectric subwavelength chiral gratings, the optical activity can be enhanced even stronger by using waveguide resonance. In the terahertz (THz) region, we obtain rotation of the polarization zimuth of a linearly polarized THz wave by using double-layered metal chiral structure with complimentary patterns.

The light transmission through metallic films with different types of nano-structures was studied both theoretically and experimentally. It is shown, analytically, numerically and experimentally, that the positions of the surface plasmon resonances depend on nano-structural details. This leads to a strong dependence of the amplitude of the light transmission, as well as the polarization of the transmitted light and other optical properties, on those details. Two complementary situations are considered: a metal film with dielectric holes and a dielectric film with metallic islands. Two different possibilities for manipulating the light transmission are considered: One is based upon application of a static magnetic field (actually, this is equivalent to changing the nano-structure in a transformed configuration space), the other is based upon using liquid crystals as one of the constituents of a nano-structured film.

We report on experimental realization of the Fang Ag superlens structure [1] suitable for further processing and integration in bio-chips by replacing PMMA with a highly chemical resistant cyclo-olefin copolymer, mr-I T85 (Micro Resist Technology, Berlin, Germany). The superlens was able to resolve 80 nm half-pitch gratings when operating at a free space wavelength of 365 nm. Fang et al. used PMMA since it enables the presence of surface plasmons at the PMMA/Ag interface at 365 nm and because it planarizes the quartz/chrome mask. If the superlens is to be integrated into a device where further processing is needed involving various organic polar solvents, PMMA cannot be used. We propose to use mr-I T85, which is highly chemically resistant to acids and polar solvents. Our superlens stack consists of a quartz/chrome grating mask, a 40 nm layer of mr-I T85, 35 nm Ag, and finally 70 nm of the negative photoresist mr-UVL 6000 (Micro Resist). A 50 nm layer of aluminium on top of the quartz/chrome mask reflected all light that did not penetrate through the mask openings thereby reducing waveguiding in the top resist layer. The exposures took place in a UV-aligner at 365 nm corresponding to the excitation wavelength of the surface plasmons at the mr-I T85/Ag interface. Supporting COMSOL simulations illustrate the field intensity distribution inside the resist as well as the presence of surface plasmons at the mr-I T85/Ag boundary. AFM scans of the exposed structure revealed 80 nm gratings.

Loss is a critical parameter in metamaterials because it determines the resolution of a super-lens made of metamaterials. The super-lensing effect observed in alternative multi-layer metamaterials consisting of metal and dielectric layers is derived from the resonant photon tunneling (RPT) via surface plasmon polaritons (SPPs). Here we demonstrates that the losses in the metamaterials can be estimated by simultaneous measurements of attenuated total reflection (ATR) and RPT. RPT through silver (Ag)/SiO₂ metamaterials is studied experimentally. A shift of the RPT peak away from the ATR dip is observed; the shift variation in an Ag/SiO₂ system is smaller than that in an aluminum/MgF₂ system. This indicates that the shift is caused by the imaginary part of permittivity, i.e., intrinsic losses, of metamaterials.

Effective magnetic permeability is investigated theoretically as well as experimentally for stratified metal dielectric metamaterial consisting of alumina (60nm) /Ag (30nm) /alumina (60nm) unit cells. The permeability calculated from complex transmission and reflection coefficients with the transfer matrix amounts to 20 just below the first photonic bandgap. Measurements with a Mach-Zehnder interferometer were found to be consistent with theoretical prediction.

As a typical uniaxial media, stratified metal-dielectric metamaterials (SMDMs) are addressed in my talk. SMDMs have diverse features: (I) Coexistence of metallic and transparent dielectric properties in SMDMs. (II) Nearly zero refractive index just above the effective plasma frequency of metallic components. This feature has enabled to design the ultracompact wave plates. (III) In case of the small ratio of metal, the transmission windows emerge which are often connected to the optical magnetism. In some particular cases, negative refractive index is also found. (IV) When the metal part is dominant, SMDMs can have the very large refractive index.

The effect of surrounding medium on the optical properties of a two layer silver film are investigated using an analytical model. We varied the media before the first layer, between the two layers, and after the second layer. We find that the optical properties of the film is dominantly determined by the medium between the two layers. The resonance wavelength red shifts when the medium between the two layers is changed from vacuum to water and then glass. The media before the first layer and after the second layer have little effect on the spectra of the film when the thicknesses of the layers are larger than 40 nm.

Metal nanoparticle assemblies of well-defined structure are investigated as substrates for quantitative surface enhanced Raman scattering (SERS). The ~100 nm structures are formed from oligonucleotide-functionalized gold core and satellite particles. Raman scattering from Cy5 incorporated on the core particles is detected before and after formation of the coupled plasmonic structures. The amplification of Raman scattering observed upon formation of the coupled structures matches quantitatively the increase in the fourth power of the surface E-field associated with coupling between particles. Raman scattering per core-satellite structure is determined by calibrating measured intensities using methanol as an intensity standard. The number of molecules that contribute significantly to the Raman signal and the mean cross section per adsorbed molecule is determined by analysis of the spatial non-uniformity of the core surface field distribution. Comparison of the wavelength dependence of the near field and the scattering spectrum using simulation reveals that the wavelengths of the maxima in near and far fields are more closely aligned for the coupled structures than for isolated cores.

The transmission properties of a barrier composed of Kerr nonlinear media contained within a photonic crystal waveguide or within circuits formed of photonic crystal waveguides is studied theoretically. The photonic crystal is a two-dimensional array of linear media dielectric cylinders, waveguides are formed in the photonic crystal by replacing a row of photonic crystal cylinders with linear media replacement dielectric cylinders, and the barrier is formed by replacing a finite number of waveguide cylinders with cylinders containing Kerr nonlinear dielectric media. The transmission maxima of the circuits, for an incident waveguide mode into the circuits, are determined as functions of two parameters characterizing the Kerr nonlinear media in the barrier. The resulting two-dimensional plot in the Kerr parameter space gives a complex pattern with features that are identified with Fabry-Perot excitations, intrinsic localized modes, and dark soliton modes resonantly excited within the barrier. Circuits treated are straight waveguides, waveguides with bends, and waveguides with side couplings. The theory is based on a difference equation approach developed for nonlinear barriers in Phys Rev B 69, 235105(2004) and Phys Rev B 77, 115105(2008).

Localized surface plasmons (LSPs) are charge density oscillations caused by an interaction of the external electromagnetic waves with the interface between metallic nanostructures (e.g. noble metal nanoparticles) and a dielectric medium. Intensity and frequency of the resulting SP absorption bands are characteristic for the type of material and depends on the size, shape and surrounding environments of the nanostructures. We have designed core/shellnanostructures with a defined Au-core and increasing Ag-shell thickness as previously described [17]. We have used AFM measurement and dark-field microscopy to characterize the nanoparticles, which were immobilized via silane chemistry on glass substrates. The plasmon band of selected particles was investigated by single particle spectroscopy (SPS) in transmission and reflection mode. Their potential as optical biosensor was demonstrated by immobilization of a protein and a protein specific antibody leading to a refractive index change in the local environment of metal nanoparticles, which causes a characteristic shift of the SP absorption band maximum.

Nano plasmonic resonance energy transfer (PRET) spectroscopy is a new sensing technique to study the electronic energy transfer between plasmonic nanoparticles and adsorbed biological/chemical molecules. PRET spectroscopy has been used to detect complex biomolecular activities including conformational change, electron transfer and protein interactions with ultrahigh sensitivity and specificity. Here we demonstrate in vitro and intracellular imaging of pH values using PRET spectroscopy. Potentially submicron spatial resolution and decimal pH sensitivity can be achieved in PRET pH imaging.

There exists a growing need for fast spatial optical phase modulators in various applications including laser communication for both terrestrial and ground-to-space communications, ultrafast laser pulse shaping as well as in medical imaging. The two principal phase spatial light modulator technologies currently available namely, liquid crystal and digital micro-mirror are limited to frame rates of a few kHz. A need therefore exists for faster MHz-range spatial phase modulating devices. Existing solid state electro-optical modulators such as based on LiNbO3 crystal, although capable of GHz rate modulation rates, cannot be used for 2-D spatial light modulation. This is due to their relatively small electro-optical coefficient which requires the use of a relatively thick layer and its associated large, (100's of Volt) modulating signal, thereby barring their practical use as spatial light or phase modulators. Surface plasmon polariton resonances which can be excited at the metal-dielectric interfaces have been shown to significantly affect both the amplitude and the phase of the traversing optical beam. In this work we present a preliminary study of metallic nanoparticles embedded in a solid state electro-optical modulator (EOM), as potential spatial phase modulating device. Here, the spatial refractive index modulation of the EOM, allows, the modulation of either amplitude of phase modulation, with the added advantage of potentially ultra-fast frame rates. The results of computer simulations, based on finite difference time domain (FDTD) method, with various nano-particle geometries are reported, describing the achievable phase modulation along with the associated absorption losses.

We present the first results of collimating the synchrotron radiation beam by zone plate located at the long distance from the source. Zone plate (ZP) has been fabricated from silicon crystal. We observe the interference fringes due to existence of various orders of focusing. We record experimentally an amplification of synchrotron beam intensity up to four times by means of ZP. The experimental measurements have been performed at the beam line BM-5 of the European Synchrotron Radiation Facility (ESRF) for the energy interval from 8 to 17.5 keV. The fringes were discussed on the base of analytical theory as well as were studied by means of computer simulation. The radial distribution of intensity is determined as a convolution of the zone plate transmission function and the Kirchhoff propagator in paraxial approximation.