This PDF file contains the front matter associated with SPIE Proceedings Volume 8423, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

The word "magic" is usually associated with movies, fiction, children stories, etc. but seldom with the natural sciences. Recent advances in metamaterials have changed this notion, in which we can now speak of "almost magical" properties that scientists could only dream about only a decade ago. In this article, we review some of the recent "almost magical" progress in the field of meta-materials.

Since Pendry's theoretical proposition of the perfect lens, extensive researches have been carried out in the field by a number of groups and various lenses and structures have been reported. In this article, we present and discuss light transmission in a vertical multilayered metal-dielectric structure and a metal chain array consisting of silver spheres with different diameters. For the incident wavelength of 660 nm, light can transmit a longer distance in the vertical multilayer structure due to low transmission loss. For the metal nanoparticle chain structure with an incident wavelength of 508 nm, the output light intensity can be greatly enhanced by adding a small sphere to the input end and output end, respectively as it is believed to enhance the coupling of the field into the structure and decoupling of the field from the structure, respectively.

We study the sharp Fano-type resonance in a dimer metamaterial based on nanorods with different lengths. Breaking the length symmetry results in the excitation of a dark mode that weakly couples to the free space. Interference between the dark mode and the higher frequency bright mode gives rise to the peculiar asymmetric and sharp profile of the resonance. The steep dispersion and high sensitivity to slight variations of the dielectric environment of this resonance envisage the possible application of the asymmetric dimer metamaterial as an optical sensor for chemical or biological analysis.

We investigate the potential of metallic metamaterials (MM) for integrated optic applications in the near-infrared (λ=1.5μm). Specifically we consider a composite guiding structure made of a MM layer over a high index slab waveguide such as silicon. In this configuration only the evanescent tail interacts with the MM layer which acts essentially as a perturbation. Our numerical simulations show that an array of gold coupled cut wires over a slab waveguide leads to a significant variation of the slab effective index in the vicinity of the resonance and thus can serve as building blocks for implementing optical functions. This geometry is compatible with current nano-fabrication technologies.

Formation and development of the photonic band gap in two-dimensional 8-, 10-, and 12-fold symmetry quasicrystalline lattices of low-index contrast are reported. Finite-size structures made of dielectric cylindrical rods are studied and measured in the microwave region, and their properties are compared with a conventional hexagonal crystal. Band-gap characteristics are investigated by changing the direction of propagation of the incident beam inside the crystal. Various angles of incidence are used to investigate the isotropic nature of the band gap.

We report on the optical properties of a layer-by-layer structure of silver nanorods, with their axes aligned perpendicular to the z direction and mutually twisted through an angle of 60° from layer to layer, by means of rigorous full electrodynamic calculations using the layer-multiple-scattering method, properly extended to describe axis-symmetric particles with arbitrary orientation. We analyze the complex photonic band structure of this crystal in conjunction with relevant polarization-resolved transmission spectra of finite slabs of it and explain the nature of the different eigenmodes of the electromagnetic field in the light of group theory. Our results reveal the existence of sizable polarization gaps and demonstrate the occurrence of strong optical activity and circular dichroism, combined with reduced dissipative losses, which make the proposed architecture potentially useful for practical applications as ultrathin circular polarizers and polarization rotators.

We consider a simplified model for a nonlinear magnetic metamaterial, consisting of a split-ring resonator (SRR) array capable of nonlinear capacitive response. We compute the localized modes around simple magnetoinductive impurities located at the bulk of the array, in closed form for both, linear and nonlinear cases. We also examine the scattering of magnetoinductive waves across internal (external) capacitive (inductive) defects coupled to the SRR array, and examine the ocurrence of Fano resonances, and how to tune them by changing the external parameters of the system. Finally, we describe a method for building a stable localized magnetoinductive mode embedded in the continous band of extended states.

We report on the fabrication of 70 nm wide, high resolution rectangular U-shaped split ring resonators (SRRs) using nanoimprint lithography (NIL). The fabrication method for the nanoimprint stamp does not require dry etching. The stamp is used to pattern SRRs in a thin PMMA layer followed by metal deposition and lift-off. Nanoimprinting in this way allows high resolution patterns with a minimum feature size of 20 nm. This fabrication technique yields a much higher throughput than conventional e-beam lithography and each stamp can be used numerous times to imprint patterns. Reflectance measurements of fabricated aluminium SRRs on silicon substrates show a so-called an LC resonance peak in the visible spectrum under transverse electric polarisation. Fabricating the SRRs by NIL rather than electron beam lithography allows them to be scaled to smaller dimensions without any significant loss in resolution, partly because pattern expansion caused by backscattered electrons and the proximity effect are not present with NIL. This in turn helps to shift the magnetic response to short wavelengths while still retaining a distinct LC peak.

Meta- material like behavior of natural Pearl are studied in this work. This work makes an attempt to analyze the Left Handed Maxwellian (LHM) properties of Pearl surface. The investigations carried out on natural Pearl specimen are optical reflectance and optical absorbance. Optical reflectance of Pearl surface with plane polarized monochromatic light in the form of verification of Fresnel equation shows distinct difference with that of conventional ordinary material. The UV-VIS analysis is also carried out for further analysis. The results obtained from the optical reflectance characteristics using polarized light indicate LHM behavior as expected for a LHM (type II or type II) meta-material. The overall analysis of the results shows the LHM character of Pearl surface.

We have investigated light propagation and Anderson localization in one-dimensional dispersive random metamaterials, focusing on the effects disorder correlation. We analyze and compare the cases where disorder is uncorrelated, totally correlated and anticorrelated. We show that the photonic gaps of the corresponding periodic structure are not completely destroyed by the presence of disorder, which leads to minima in the localization length. We demonstrate that, in the vicinities of a gap of the corresponding periodic structure, the behavior of the localization length depends crucially on the physical origin of the gap (Bragg or non-Bragg gaps).

Asymmetric split ring resonators (A-SRRs) are formed when two separate metallic arcs of different lengths share the same centre-of-curvature. The resonances of the two arcs interact to produce steep slopes in the reflection spectrum. Due to their size they are also known as nano antennas. By depositing very thin films of poly-methyl-methacrylate (PMMA), a shift in resonance reflection spectra is obtained. Similarly, it is known that the spectral position of the A-SRR resonances can be tuned with size. We show that, when PMMA is used as an organic probe (analyte) on top of an A-SRR array, the phase and amplitude of a characteristic molecular bond resonance associated with PMMA changes the appearance of the observed Fano resonance, according to the spectral position of the plasmonic reflection peaks. This effect can be utilized to give characteristic signatures for the purpose of detection. We also show the effectiveness of localizing different blocks of PMMA at different places on the A-SRR array to detect very small amounts of non-uniformly distributed analytes. Finally we show that even though the resonance Q-factor is much smaller when compared to values achievable in photonic crystal microcavities, the plasmonic nano-antenna arrays can be used to provide highly sensitive detection of organic compounds.

We present the selected results of theoretical and experimental investigations of high-performance ultra-thin metamaterial-inspired absorbers designed for narrow-band operation at subterahertz frequencies and intended for integration with spectrally-selective bolometric devices. The attainability of values up to 182 for the ratio of the free-space wavelength to the absorber's thickness is experimentally demonstrated, while realizability of even thinner structures is shown. The first prototypes of spectrophotometric and imaging detectors with metamaterial-based radiation-sensitive pixels, utilizing a principle of THz-to-IR conversion, are discussed.

We show that subwavelength diffracted wave fields may be managed inside multilayered plasmonic devices to achieve ultra-resolving lensing. For that purpose we first transform both homogeneous waves and a broad band of evanescent waves into propagating Bloch modes by means of a metal/dielectric (MD) superlattice. Beam spreading is subsequently compensated by means of negative refraction in a plasmon-induced anisotropic effective-medium that is cemented behind. A precise design of the superlens doublet may lead to nearly aberration-free images with subwavelength resolution in spite of using optical paths longer than a wavelength.

We present recent progress in nondiffracting subwavelength fields propagating in complex plasmonic nanostructures. In particular, diffraction-free localized solutions of Maxwell's equations in a periodic wire medium are discussed thoroughly. The Maxwell-Garnett model is used to provide analytical expressions of the electromagnetic fields for Bessel beams directed along the cylinders axes. Large filling factors of the metallic composite induce resonant-plasmonic spots with a size that remains far below the limit of diffraction. Some numerical simulations based on the finite-element method support our analytical approach.

We demonstrate thermal and ultrafast optical tuning in planar terahertz (THz) superconducting metamaterials. The fundamental resonance of an array of split-ring resonators (SRRs) fabricated from a 50-nm-thick high-temperature superconducting (HTS) YBa₂Cu₃O_7-δ (YBCO) film is characterized as a function of temperature and near-infrared photoexcitation fluence. The HTS metamaterial exhibits a very strong resonant response at temperatures much lower than the transition temperature T_c. Increasing the temperature reduces the density of Cooper pairs, which results in a dramatically decreasing imaginary part of the complex conductivity, and thereby tunes the metamaterial resonance. We observe switched resonance strength and large red shift of resonance frequency when the temperature increases from 20 K to T_c. Similar resonance switching and frequency tuning is also demonstrated in an ultrafast time scale through near-infrared femtosecond laser excitation. We further compare the thermal tuning behaviour of the 50-nm-thick HTS metamaterial with a metamaterial sample comprised of gold SRRs with identical geometry and dimensions, which has negligible tunability.

We report our latest results on second harmonic generation (SHG) microscopy from arrays of G-shaped chiral gold nanostructures. The nanostructures are arranged in unit cells composed of four Gs, each rotated at 90° with respect to its neighbors. As it has already been demonstrated, for linearly polarized light, these unit cells yield a pattern of four SHG hotspots. However, upon increasing the pitch of the nanostructured arrays, extra hotspots can be observed at the edges of the unit cells. While the origin of these extra hotspots remains to be elucidated, their position indicates a relationship to coupling behavior between the unit cells.

The concept of broadband extraordinary optical transmission (EOT) through metallic gratings at the plasmonic Brewster angle has recently been introduced. It is based on the ultrabroadband impedance matching between guided modes supported by ultranarrow slits in a one-dimensional (1D) metallic grating and an incident transverse magnetic (TM) wave. The overall mechanism results in total transmission through such a corrugated plasmonic screen. This concept was first demonstrated in 1D metallic gratings and it can also be extended to two-dimensional (2D) periodic metallic gratings made by either multiple rectangular or cylindrical rods. In this contribution, we review this concept and we demonstrate that this phenomenon can be applied to semiconductor gratings, whose materials have plasmonic properties at THz frequencies. This may open several opportunities to develop low-loss, broadband optical metamaterials for energy harvesting and concentrators.

Periodic single metallic meander structures have been shown to exhibit extraordinary transmission in the visible frequency domain within a well-defined pass band that can be shifted by geometry variation. Furthermore, meander structures are not only linear polarizers but also induce phase retardation between s- and p-polarized light. In addition, they are able to convert the polarization of light due to plasmonic excitations. Those features combined with the advantages of plasmonic metamaterials in general, such as radiation stability, temperature independence and low weight make them perfect candidates for optical devices in space instruments. We show analytically and numerically that an optical depolarizer can be designed by spatially distributing meander structures in a pixel-like fashion and rotating each element by a random angle. The depolarizing properties of meander structures, indicated by the Mueller matrix elements, are investigated for various geometrical parameters and can be improved by stacking two meander structures onto each other. The presented polarization scrambler can be flexibly designed to work anywhere in the visible wavelength range with a bandwidth of up to 100 THz. Furthermore, the depolarization effect relies on optical activity rather than scattering. With our preliminary design, we achieve depolarization rates larger than 60% for arbitrarily polarized, monochromatic or narrow-band light, respectively. One advantage of our concept is the flexibility to tune the polarization scrambler to a particular optical frequency or functionality. Circularly polarized light (S = [1, 0, 0, ±1]) for instance could be depolarized by 95% at 600 THz.

Self-assembly techniques are used to build complex amorphous structures from plasmonic particles. The assembly makes use of surface chemistry and intermolecular interactions between surfaces, surfactants, polymers and particles. The resulting two- or three-dimensional structures have optical properties that derive from the coupling between particles. A high control of the structural parameters on the nanometer scale can easily be achieved. In contrast to top-down techniques relatively large areas can be prepared in a versatile manner thus paving the way to applications as functional devices. Several structures are discussed such as layered arrays of gold nanoparticles, core-shell structures and hierarchical structures. The optical properties of these structures are also presented and compared with simulations. Some of the structures are of interest for plasmonic cloaking whereas other might find applications as substrates for sensing by surface-enhanced Raman spectroscopy.

This paper is dedicated to the study of plasmonic cloaking, based on the use of appropriate core-shell systems that may act as a cloaking devices for a finite range of frequencies. This cluster consists of an amorphous arrangement of metallic (gold or silver) and/or polaritonic nano-particles, which could be approximated in the quasistatic limit by an effective medium, having interesting properties such as a negative or very low permittivity and/or permeability in the optical domain with moderate losses. We first derive the effective properties of a shell made of such small spheres using the Maxwell-Garnett and Clausius-Mosotti formulas. We then numerically show that a dielectric core sphere is almost made invisible at optical frequencies with a scattering reduction of more than 70 percent. We finally derive some analytical expressions that we have compared to rigorous numerical simulations.

We discuss the concept of infrared cloaking using nanosphere dispersed liquid crystal (NDLC) matematerial in cylindrical geometry for TM polarization. The system consists of layers of NDLC with different values of ordinary refractive index and the same value of extraordinary refractive index of liquid crystal host. Finite element calculations (COMSOL Multiphysics), which include the Poynting vector calculations, show that scattering from the hidden object is limited in the presence of the layered cloak.

Based on the analogy between the Maxwell equations in complex metamaterials and the free-space Maxwell equations on the background of an arbitrary metric, transformation optics allows for the design of metamaterial devices using a geometrical perspective. This intuitive geometrical approach has already generated various novel applications within the elds of invisibility cloaking, electromagnetic beam manipulation, optical information storage, and imaging. Nevertheless, the framework of transformation optics is not limited to three-dimensional transformations and can be extended to four-dimensional metrics, which allow for the implementation of metrics that occur in general relativistic or cosmological models. This enables, for example, the implementation of black hole phenomena and space-time cloaks inside dielectrics with exotic material parameters. In this contribution, we present a time-dependent metamaterial device that mimics the cosmological redshift. Theoretically, the transformation-optical analogy requires an innite medium with a permittivity and a permeability that vary monotonically as a function of time. We demonstrate that the cosmological frequency shift can also be reproduced in more realistic devices, considering the fact that practical devices have a nite extent and bound material parameters. Indeed, our recent numerical results indicate that it is possible to alter the frequency of optical pulses in a medium with solely a modulated permittivity. Furthermore, it is shown that the overall frequency shift does not depend on the actual variation of the permittivity. The performance of a nite frequency converter is, for example, not aected by introducing the saw tooth evolution of the material parameters. Finally, we studied the eect of the introduction of realistic metamaterial losses and, surprisingly, we found a very high robustness with respect to this parameter. These results open up the possibility to fabricate this frequency converting device with currently available metamaterials [V. Ginis, P. Tassin, B. Craps, and I. Veretennico, Opt. Express 18, 5350{5355 (2010)¹].

We study second harmonic generation from dipole gold nanoantennas by analyzing the different contributions of bulk and surface nonlinear terms. Numerical calculations have been performed applying a Green's tensor method. The SHG as a function of the wires cross section size is investigated in both the near and far field regimes. We show that the excitation of localized surface plasmon polaritons in these structures can remarkably modify the nonlinear response of the system by enhancing surface and/or bulk contributions, creating regimes where bulk nonlinear terms dominate over surface linear terms and vice versa. We also report results of calculations performed on Silver coupled 2D-nanoresonators. Coupling is responsible for the formation of resonant modes that can be localized on small portions of the structure or distributed over the whole structure.

An array of rf SQUIDs (Superconducting Quantum Interference Devices) in an alternating magnetic field can operate as a magnetic metamaterial where the phase and group velocities have opposite signs. In this system, discreteness and nonlinearity may lead to the generation of intrinsic localized modes in the from of discrete breathers. These breathers result from a balance of incoming power and losses, and they may change locally the response of a SQUID array to an applied field from diamagnetic to paramagnetic or vice-versa. We derive the dynamic flux equations for the damped and driven SQUID array and integrate them in the weak-coupling approximation to demonstrate the existence of various kinds of dissipative breathers. Besides using standard algorithms for breather construction, we have also observed the spontaneous breather generation in weakly disordered SQUID arrays. Moreover, low-energy breather-like pulses may be generated in end-driven arrays which propagate for fairly long distances in a dissipative environment. A short account on the tunability of the resonance of individual SQUIDs by application of either constant and/or alternating fields is also given.

In the recent decade metamaterials with magnetic permeability different than unity and unusual response to the magnetic field of incident light have been intensively explored. Existence of magnetic artificial materials created an interest in a scanning near-field magnetic microscope for studies of magnetic responses of subwavelength elementary cells of those metamaterials. We present a method of measuring magnetic responses of such elementary cells within a wide range of optical frequencies with single probes of two types. The first type probe is made of a tapered silica fiber with radial metal stripes separated by equidistant slits of constant angular width. The second type probe is similar to metal coated, corrugated, tapered fiber apertured SNOM probe, but in this case corrugations are radially oriented. Both types of probes have internal illumination with azimuthally polarized light. In the near-field they concentrate into a subwavelength spot the longitudinal magnetic field component which is much stronger than the perpendicular electric one.

In this work, we show that closely-spaced gold nanohoops periodically distributed in a square lattice can provide a strong magnetic response in the near infrared regime when illuminated under normal incidence (perpendicular to the structure plane). Therefore, just a single metallic layer is needed to achieve the magnetic activity. A key point to achieve this response is that the aspect ratio must be higher than 1. Transmission and reflection spectra taken by means of a Fourier-Transform Infrared spectrometer show a strong absorbance peak at a wavelength that can be tuned by modifying the hole radius of the nanohoops or the underlying dielectric substrate. Numerical simulations show that at the resonance wavelength a virtual current loop is created, giving rise to a strong magnetic moment and a large magnetic field enhancement in the space between nanohoops.

We investigate spatial-dispersion properties of hybrid surface waves propagating in the boundary of a semi-infinite layered metal-dielectric nanostructure. Electromagnetic fields can be dramatically affected by a nonlocal optical response of the plasmonic lattice. We demonstrate that the use of the so called effective medium approximation (EMA) is not justified if the thickness of a metallic layer becomes of the order of the metal skin depth. We compare the results obtained by means of EMA with computer solutions of Maxwell's equation, including losses in the metal.

We report an analytic approach to describe all-dielectric graded periodical media (namely graded photonic crystals) operating in the homogeneous regime. Beneath this condition, the method is based on the equations of Hamiltonian optics and provides an analytical expression of the two-dimensional refraction index needed to make light follow prescribed paths. It is applied to a proof-of-concept structure (light 90° bend), which behaviour is investigated by considering a two-dimensional planar silicon on insulator slab waveguide drilled by a sub-wavelength air-hole lattice with a gradual filling factor corresponding to the required optical index map. The electromagnetic properties of the considered structure are then verified using Finite Difference Time Domain simulation. As a whole, the proposed method is an alternative solution to conformal space coordinate transforms applied to all-dielectric photonic metamaterials and could help the design of new structures in forthcoming works.

Recent disclosures on subwavelength plasmonic crystals, like the potential excitation of a pair of coexisting wave-fields with opposite refraction, only can be understood by considering two dispersion branches with completely different features that characterize the metamaterial. One branch gives elliptic-like dispersion and the other provides hyperbolic-like dispersion. However the effective medium approximation, also known as Rytov approximation, is not consistent with both curves simultaneously. We follow an approach leading to a single curve that allows a complete description of both diffraction behaviors concurrently. Importantly only two parameters of the closed curve, together with the lattice period, fulfill such a complete picture. In addition, our semi-analytical approach may include more general situations straightforwardly.

The properties of new optical waveguides with nanosize cross-section made of noble metals and glasses are described. As was found, this waveguide supports propagation of modes with unusual propagation properties. For estimation of the field localization, losses, propagation length, velocity and others characteristics the numerical simulations by FEM method has been used. The set of advanced structures are studied: a conventional coaxial; a coaxial waveguide with periodically arrange metal tubes for reducing the metal part in the structure; the coaxial waveguides with elliptic-type central rod and two cross ellipses. The effects of the asymmetry of the central part those structures have been estimated. The comparison of the results of this investigation by wavelength deviation has been performed. A combination of noble metal plus active glasses has been estimated towards minimization of losses. The power flow distribution for different types of modes is investigated. The best characteristics can be achieved for the dipole-like modes which can be excited by an external dipole.

In this work we address the phonon-polariton band gap study in periodic and quasi-periodic (Fibonacci-type) multilayers made up of both positive (SiO2) and negative refractive index materials (metamaterials) following the Fibonacci sequence in the terahertz region. The behavior of the polaritonic band gaps as a function of the multilayer period is investigated. Our theoretical model makes use of a transfer matrix approach to simplify the algebra involved and to set up analytical phonon-polariton dispersion relations (bulk and surface modes). We also present a quantitative analysis of the results, pointing out the distribution of the allowed polaritonic bandwidths for high Fibonacci generations. An analysis of the connement eects arising from the competition between the long-range aperiodic order, induced by the quasi-periodic structure, and the short-range disorder, are made, yielding a good insight about they localization and power law of the polaritonic modes.

Plasmonic microcavities are compact systems having the capability to confine light in an extremely small volume. Light matter interactions can therefore be mediated very effectively by them. In this report we demonstrate experimentally that dispersion of photonic cavity modes can be tuned to a large degree in a plasmonic microcavity with two identical corrugated metallic films as resonant mirrors. The modification of the dispersion is induced by interactions between the photonic and plasmonic modes. Additionally, the excited surface waves are strongly enhanced by the gratings, which is important for coupling and enhancing evanescent fields. To realize such a cavity, we employed self-assembled monolayer nanosphere crystals as a prepatterned substrate. Metal/dielectric/metal films were subsequently deposited on it. The cavity length was used to tune the interaction strength. As a result, the original positively dispersive FP mode, i.e., the resonance frequency is increased with the incident angle, becomes independent or even negatively dependent on the incident angle. Due to the hexagonal textured corrugation of the metal film and the existence of some line defects in a large area, the optical response is isotropic and independent of the specific polarization. This behavior can have potential applications for light emission devices, plasmonic color filters and subwavelength imaging.