This PDF file contains the front matter associated with SPIE Proceedings Volume 8455, including the Title Page, Copyright Information, Table of Contents, and the Conference Committee listing.

We demonstrate reduced reflectance and a corresponding enhancement of transmittance in lamellar hyperbolic metamaterials, with scatterers deposited on the top. The effect is much more significant in curvilinear hyperbolic metamaterials. We also show that absorption strengths of dyes on the top of hyperbolic metamaterials can be tuned and enhanced (nearly threefold). The effect can be controlled by interplay of the substrate geometry, composition and location of the absorbing medium. Our observations pave the way for a variety of applications, including broadband enhancements of light trapping and absorption in solar cells.

Nonlinear metamaterials have received considerable attention in recent years. The inclusion of nonlinear and active effects in metamaterials expands the possibilities for engineering media with designer properties. We detail our recent efforts to create nonlinear and active metamaterials at RF with useful properties through the inclusion of embedded nonlinear or active elements. We demonstrate some of the possible applications of such nonlinear and active metamaterials experimentally, with properties including saturable absorption, phase conjugation, and power harvesting.

In various metamaterials, surface plasmon polaritons (SPPs) play important roles to produce novel electromagnetic functions through the field enhancement, the dispersion modification, and the frequency tunability. Here, we apply the function of the SPP to a color 3D image display with white-light back-illumination. We reconstructed the color image from a hologram with white-light by using SPP. The hologram is recorded as corrugations of a silver film, which is covered by a SiO₂ film to modify the color dispersion of the SPP. A single-color light in the white-light is separated as the SPP owing to the color dispersion. The SPP is diffracted by the hologram to reconstruct the three dimensional wavefront with the selected color. To obtain a multi-color image, RGB-color holograms are recorded with azimuthal-angle multiplex and are reconstructed simultaneously. The silver is used as the metal film so that the SPP of whole visible region can be excited. The silver film is 55-nm thickness, in which the SPP is excited efficiency. The SiO₂ film enhances color selectivity, but if its thickness overs 25-nm, SPP in high optical frequency such as blue vanishes. Corrugation depth is up to 25-nm, within which brightness of the image monotonically increases with the depth. If the depth overs the 25-nm, the brightness is decreased. The SPP on the corrugated silver surface and SiO₂ film have made color selectivity to a thin hologram. The SPP color holography gives a new white-light reconstruction technique using back-lighting.

Metamaterials with a hyperbolic dispersion curve, called hyperbolic metamaterials, exhibit an amazing broad-band singularity in the photonic density of states in the usual local-response approximation. In this paper, under the framework of the hydrodynamic Drude model, we discuss the effects of the nonlocal response of the electron gas in the metal on the hyperbolic metamaterials. By using mean field theory, we derive the effective material parameters of the hyperbolic metamaterials. The original unbounded hyperbolic dispersion is found to be cut off at the wavevector inverse to the Fermi velocity. By expanding the Green function in a plane-wave basis and using the transfer matrix method to calculate the reflection coefficients, we study the local density of states (LDOS) of hyperbolic metamaterials. We show that the nonlocal response of the electron gas in the metal removes the singularity of both radiative and non-radiative local density of states, and also sets up a finite maximal value. We also briefly discuss the effects of the nonlocal response on other plasmonic structures, such as a metallic semi-infinite substrate and a metallic slab.

We investigate conditions for Casimir Force (CF) reversal between two parallel half-space metamaterial plates separated by air or vacuum at ambient temperatures. Practically, the Casimir effect can lead to stiction in nanoscale devices, degradation and decreased performance. While material realizations of repulsive CF has been proposed for high dielectric host materials, so far the CF reversal with air/vacuum as intermediate medium remain challenging. Here, we propose a two plate design based on artificial electromagnetic materials known as metamaterials. This configuration allows a simple analytical treatment that accurately describes the large and short distance asymptotics of CF and allows extraction of important parameters such as lower and upper cutoff gap distances that define the repulsive force window. A parametric study has been performed in terms of the plate's dielectric and magnetic plasma frequencies, plate separation distance and temperature. The parametric domain for achieving CF reversal is identified. If successfully implemented the proposed design could potentially result in frictionless bio-fluid transport devices, quantum levitation and coating for ultra-clean room environment.

Radiation pressure and photon momentum in negative-index media are no different than their counterparts in ordinary (positive-index) materials. This is because the parameters responsible for these properties are the admittance √ε /μ and the group refractive index n_g of the material (both positive entities), and not the phase refractive index n =√με , which is negative in negative-index media. One approach to investigating the exchange of momentum between electromagnetic waves and material media is via the Doppler shift phenomenon. In this paper we use the Doppler shift to arrive at an expression for the radiation pressure on a mirror submerged in a negative-index medium. In preparation for the analysis, we investigate the phenomenon of Doppler shift in various settings, and show the conditions under which a so-called “inverse” Doppler shift could occur. We also argue that a recent observation of the inverse Doppler shift upon reflection from a negative-index medium cannot be correct, because it violates the conservation laws.

In a recent paper, we questioned the validity of the Lorentz law of force in the presence of material media that contain electric and/or magnetic dipoles. A number of authors have criticized our methods and conclusions. This paper is an attempt at answering the critics and elaborating the relevant issues in some detail.

The opportunities presented by the use of metamaterials have been the subject of extensive discussions. However, a large fraction of the work available to date has been limited to simulations and proof-of-principle demonstrations. One reason for the limited success inserting these structures into functioning systems and real-world applications is the high level of complexity involved in their fabrication. Most approaches to the realization of metamaterial structures utilize traditional lithographic processing techniques to pattern the required geometries and then rely on separate steps to assemble the final design. Obviously, composite structures with arbitrary and/or 3-D geometries present a challenge for their implementation with these approaches. Non-lithographic processes are ideally suited for the fabrication of arbitrary periodic and aperiodic structures needed to implement many of the metamaterial designs being proposed. Furthermore, non-lithographic techniques are true enablers for the development of conformal or 3-D metamaterial designs. This article will show examples of metamaterial structures developed at the Naval Research Laboratory using non-lithographic processes. These processes have been applied successfully to the fabrication of complex 2-D and 3-D structures comprising different types of materials.

Spontaneous emission of a dipole can be significantly modified in metamaterials, providing opportunities to engineer emission rates, yields, spectra, and angular patterns. To better understand specifics of such modifications for electric and magnetic emitters, we study luminescence of Eu³⁺ ions placed in a close vicinity of arrays of gold nanostrips. The luminescence is strongly polarized, with the preferable polarization parallel to the direction of strips. Polarization patterns and angular distributions of radiation depend on wavelength, and are different for electric and magnetic dipole transitions. The results are discussed in terms of different coupling of emitters with radiative and high-loss modes.

In this work, we show that natural crystals, or magnetic semiconductor, Cr-doped indium oxide, has a negative refractive index at ~ 27.8 micron wavelength. The effect was predicted by two of us a few years ago (A.G. Kussow and A. Akyurtlu, Phys. Rev. B, 78, 205202 (2008)). Our result seriously undermines wide-spread opinion that only composite artificial metamaterials can demonstrate negative refractive index. Thin ferromagnetic films of ICO were fabricated by original post-annealing sputtering method. FTIR R and T measurements were processed to extract refractive index within the range of interest. The extracted from combined transmittance and reflectance FTIR data negative refractive index band parameters are found to be close to expected one.

A theoretical framework to analyze the optical properties of amorphous metamaterials made from meta-atoms which are amenable for a fabrication with bottom-up technologies is introduced. The achievement of an isotropic magnetic resonance in the visible is investigated by suggesting suitable designs for the meta-atoms. Furthermore, two meta-atoms are discussed in detail that were fabricated by self-assembling plasmonic nanoparticles using techniques from the field of colloidal nanochemistry. The metamaterials are experimentally characterized by spectroscopic means and the excitation of the magnetic dipole moment is clearly revealed. Advantages and disadvantages of metamaterials made from such meta-atoms are discussed.

Leonhardt demonstrated (2009) that the 2D Maxwell Fish Eye lens (MFE) can focus perfectly 2D Helmholtz waves of arbitrary frequency, i.e., it can transport perfectly an outward (monopole) 2D Helmholtz wave field, generated by a point source, towards a receptor called “perfect drain” (PD) located at the corresponding MFE image point. The PD has the property of absorbing the complete radiation without radiation or scattering and it has been claimed as necessary to obtain super-resolution (SR) in the MFE. However, a prototype using a “drain” different from the PD has shown λ/5 resolution for microwave frequencies (Ma et al, 2010). Recently, the SR properties of a device equivalent to the MFE, called the Spherical Geodesic Waveguide (SGW) (Miñano et al, 2012) have been analyzed. The reported results show resolution up to λ /3000, for the SGW loaded with the perfect drain, and up to λ /500 for the SGW without perfect drain. The perfect drain was realized as a coaxial probe loaded with properly calculated impedance. The SGW provides SR only in a narrow band of frequencies close to the resonance Schumann frequencies. Here we analyze the SGW loaded with a small “perfect drain region” (González et al, 2011). This drain is designed as a region made of a material with complex permittivity. The comparative results show that there is no significant difference in the SR properties for both perfect drain designs.

We propose an innovative cloak to enable different sizes, shapes and also constituent parameters of arbitrary hidden objects not only to observe the fields with 360-degree eyesight from the environment outside the cloak but also to need neither to be ‘custom-made’ nor to be confined by the position of the corresponding anti-objects. We design the spatially varying constituent parameters of an innovative cloak by the aid of transformation optics with two steps of coordinate transformations and testify the performances of an innovative cloak by COMSOL simulation software. Herein, we demonstrate the corresponding Ez field distribution as a testimony of invisible hidden objects and claim that the simulation results demonstrate a good agreement with analytical study of an innovative cloak.

We demonstrate a flexible thin film zero refractive index optical metamaterial with matched impedance to free space and low absorption loss at 1.55 μm. The metallo-dielectric multilayer structure with fishnet geometry was optimized by a genetic algorithm. The fabrication process and characterization approach are described. The experiment results agree well with the theoretical predictions, showing an effective index of n_eff = 0.072 + 0.51i and an impedance of Z_eff/Z₀ = 1.009 – 0.021_i.

Two major types of optical cavities are in wide-use today: photonic crystals and optical microcavities. However, both of these systems have major drawbacks. Photonic crystals only operate for a certain range of wavelengths while optical microcavities can only trap light for a certain range of angles determined by the microcavity angle of total internal reflection. Here, new types of optical cavities are proposed and investigated, aiming to resolve these problems by providing Lyapunov-stable photon orbits within a specially designed inhomogeneous isotropic/anisotropic media. These types of optical traps, referred to as a Continuous Index Photon Traps (CIPTs), seek to exploit recent advances in the field of optics. Specifically, nanofabricating artificial optical materials, i.e. metamaterials, that can bend light and entrap photons in a finite spatial domain. The CIPT’s potential to provide stable photon orbits is assessed. Material realizations of the proposed photon traps are suggested and their optical properties including cavity Q-factors and decay rates are estimated. Potentialy important practical applications of the CIPTs would include optical cavities that trap light withough use of refraction index discontiniuties and hence have low scattering losses due to surface roughness.

For one-dimensional photonic bandgap structures consisting of alternating layers of positive and negative index materials, Anderson localization effects will appear when one or more parameters is disordered. Such long randomly disordered systems can be modeled via a long chain of independent identically distributed random matrices. The Lyapunov exponent of such a random matrix product characterizes the energy confinement due to Anderson localization. Furstenberg’s integral formula gives, at least theoretically, the Lyapunov exponent precisely. Furstenberg’s integral formula requires integration with respect to the probability distribution of the randomized layer parameters, and integration with respect to the so-called invariant probability measure of the direction of the vector propagated by the long chain of random matrices. This invariant measure can rarely be calculated analytically, so some numerical technique must be used to produce the invariant measure for a given random matrix product model. Here we use the Froyland-Aihara method to find the invariant measure. This method estimates the invariant measure from the left eigenvector of a certain sparse row-stochastic matrix. This sparse matrix represents the probabilities that a vector in one of a number of discrete directions will be transferred to another discrete direction via the random transfer matrix. This paper, possibly for the first time, presents the numerically calculated invariant measure for a discretely disordered one-dimensional photonic bandgap structure which includes negative index material in alternating layers. Results are compared with the structure containing all positive index layers, as well as with the counterpart structure in which random variables are drawn from a uniform probability density function.

The pulsed laser deposited nanocrystalline ZnO films doped by Ga up to six weight percent are studied by X-ray difraction and generalized spectro-ellipsometry. We report substantial atomic structure modification of heavy Ga-doped ZnO resulted and a concentration dependent increase of inter-planar distance. Measured dielectric function spectra show strong blue-shift of the samples studied. Equilibrium atomic configurations and electron energy structure of ZnO containing defects (voids and Ga impurities) are studied by the density functional theory (DFT) and generalized gradient approximation (GGA). Atomic geometries are obtained from the total energy minimization method. Optical functions are calculated within the random phase approximation including the quasi-particles corrections and plasma excitation effects. We report energetically favorable paths of the voids growth and aggregation in ZnO. Comparative analysis of experimental and theoretical results indicate that measured blue-shift in ZnO:Ga substantially exceeds the Burstein-Moss shift as used in many previous work to interpret concentration dependence of optical functions in heavy doped ZnO. We demonstrate that additional mechanisms, such as structural and alloying effect, should be involved for quantitative interpretation of optics of the nano-crystalline heavy-doped ZnO films.

We demonstrate a composite metamaterial composed of two asymmetrically oriented π-shaped structures that exhibits plasmonic analogue of electromagnetically induced transparency (EIT). The structure exhibits fine tuning of EIT-like spectral behavior and spatial control of near-field intensity distribution. Originated from the asymmetric design, we introduce a more compact system which possesses the similar EIT-like spectral response as well as much smaller optical mode volumes.

We demonstrate the use of liquid crystal infiltration of fishnet structures for the realization of highly tunable and nonlinear optical metamaterials. We show that fishnet metamaterials infiltrated with nematic liquid crystals can exhibit strong nonlinear response at moderate laser powers. We also show that this nonlinear response arises due to the molecular orientation of the liquid crystal molecules and can be therefore be fine-tuned with an electric field, opening new opportunities for electrically tunable nonlinear metamaterials.

Using active loads in circuits that result in negative differential resistances at various nodes in the circuit are used for producing resistance cancellation, gain, oscillations, and other types of effects not seen in passive circuits. We aim to demonstrate these properties in metamaterial unit cells with the hope of mimicking the circuit behavior in bulk media. In the metamaterial unit cells, we were able to experimentally show resistance cancellation by controlling the quality of the resonance of the unit cell, oscillation and harmonic generation in the unit cell, and mixing within the unit cell between incident signals and the self generated oscillations and harmonics.

Long-wave IR transmission spectra of crystal KTm(MoO₄)₂ have been measured in polarized light (Е║а and Е║с) at T=6К in the energy range 10-40 cm^-1. Two vibration modes with energy 18.5 cm^-1 in polarization Е║а and with energy 25.5 cm^-1 in polarization Е║с have been found. The structure of low-frequency vibration spectrum in the Brillouin zone was calculated using a one-dimensional model. The dependences of microwave radiation transmission in crystal KTm(MoO₄)₂ on the external magnetic field were measured in the frequency range 90-333 GHz at low temperatures (Т=2K). It is revealed that in addition to the absorption band caused by the excitation of Tm³⁺ ions from the ground state to the first Stark level, the transmission spectrum contains peaks in the form of sidebands. This structure is assumed to result from the dynamic coupling between the low-energy electron excitation of Tm³⁺ ions and the acoustic vibrations of the crystal lattice.

We consider one-dimensional photonic bandgap structures with negative index of refraction materials modeled in every layer, or in every other layer. When the index of refraction is randomized, and the number of layers becomes large, the light waves undergo Anderson localization, resulting in confinement of the transmitted energy. Such a photonic bandgap structure can be modeled by a long product of random transfer matrices, from which the (upper) Lyapunov exponent can be calculated to characterize the localization effect. Furstenberg’s theorem gives a precise formula to calculate the Lyapunov exponent when the random matrices, under general conditions, are independent and identically distributed. Specifically, Furstenberg’s integral formula can be used to calculate the Lyapunov exponent via integration with respect to the probability measure of the random matrices, and with respect to the so-called invariant probability measure of the direction of the vector propagated by the long chain of random matrices. It is this latter invariant probability measure, so fundamental to Furstenberg’s theorem, which is generally impossible to determine analytically. Here we use a bin counting technique with Monte Carlo chosen random parameters from a continuous distribution to numerically estimate the invariant measure and then calculate Lyapunov exponents from Furstenberg’s integral formula. This result, one of the first times an invariant measure has been calculated for a continuously disordered structure made of alternating layers of positive and negative index materials, is compared to results for all negative index or equivalently all positive index structures.

Commonly, metamaterials are electrically engineered systems with optimized spatial arrangement of subwavelength sized metal and dielectric components. We explore alternative methods based on use of magnetic inclusions, such as magnetic nanoparticles, which can allow permeability of a composite to be tuned from negative to positive at the range of magnetic resonance. To better understand effects of particle size and magnetization dynamics, we performed electron magnetic resonance study on several varieties of magnetic nanoparticles and determined potential of nanoparticle use as building blocks for tunable microwave metamaterials.

The ideas of employing the unique properties of metamaterials for cloaking and invisibility applications has been recently suggested and investigated by several groups, because they may find numerous applications in physics and technology. While many of the recent designs of the cloaking structures are based on the transformation optics and exact formulas, the original concept suggested by Tretyakov employed the periodical set of parallel-plate waveguides with the height smoothly varying from H to h in order to reduce drastically the total scattering cross-section of a given object and to obtain broadband cloaking effect. Our paper is devoted to improvement of this design to make tunability and nonlinear effect. The Tretyakov’s design was scaled for Ku-band frequencies and the cloak was placed into rectangular waveguide. The broad transmission band (“invisibility region”) was obtained. The tunability of transmission band was realized by addition the capacitors into the cloak, between metallic plates. The cloaking system was simulated numerically by CST Microwave Studio. The possibility of invisibility switching on/off was shown by changing of capacity of varactor diodes from 0.4 to 3.4 pF by incident power. The nonlinear cloak behavior was shown at microwaves.