This PDF file contains the front matter associated with SPIE Proceedings Volume 8806, including the Title Page, Copyright information, Table of Contents, Invited Panel Discussion, and Conference Committee listing.

We show how transformation optics can enhance optical gradient forces between two optical waveguides by several orders of magnitude. The technique is based on a coordinate transformation that alters the perceived distance between the waveguides. This transformation can be implemented using single-negative metamaterial thin films. The process is remarkably robust to the dissipative loss normally observed in metamaterials. There- fore, our results provide an alternative way to enhance optical forces in nanophotonic actuation systems and may be combined with existing resonator-based enhancement methods to produce optical gradient forces with unprecedented amplitude [Phys. Rev. Lett. 110, 057401 (2013)].

We report on a numerical study of a new bianisotropic parameter retrieval technique for both regular and complementary V-shape antenna metasurfaces. Each antenna element with a discrete phase shift is modeled by a homogenous bianisotropic film to represent the optical response. For the complementary design, the retrieval implies a complementary behavior of effective material properties and predicts the analogous functionalities. Further, FDFD solver is developed to integrate the bianisotropic descriptions of each antenna and describes a fully functional metasurface. The computational burden is significantly reduced, because effective material properties replace the detailed meshing of the antennas. Experimentally, large dimension arrays of nano‐voids are fabricated using electron beam lithography. It is demonstrated that cross-polarized light is diffracted towards the same direction. Furthermore, the complementary design greatly increases the extinction ratio of functional fields to background fields.

A honey-comb monolayer lattice of carbon atoms, graphene, is not only ultra-thin, ultra-light, flexible and strong, but also highly conductive when doped and exhibits strong interaction with electromagnetic radiation in the spectral range from microwaves to the ultraviolet. Moreover, this interaction can be effectively controlled electrically. High flexibility and conductivity makes graphene an attractive material for numerous photonic applications requiring transparent conducting electrodes: touchscreens, liquid crystal displays, organic photovoltaic cells, and organic light-emitting diodes. Meanwhile, its tunability makes it desirable for optical modulators, tunable filters and polarizers. This paper deals with the basics of the time-domain modeling of the graphene dielectric function under a random-phase approximation. We focus at applicability of Padé approximants to the interband dielectric function (IDF) of single layer graphene. Our study is centered on the development of a two-critical points approximation (2CPA) of the IDF within a single-electron framework with negligible carrier scattering and a realistic range of chemical potential at room temperature. This development is successfully validated by comparing reflection and transmission spectra computed by a numerical method in time-domain versus semi-analytical calculations in frequency domain. Finally, we sum up our results - (1) high-quality approximation, (2) tunability, and (3) second-order accurate numerical FDTD implementation of the 2CPA of IDF demonstrated across the desired range of the chemical potential to temperature ratios (4 - 23). Finally, we put forward future directions for time-domain modeling of optical response of graphene with wide range of tunable and fabrication-dependent parameters, including other broadening factors and variations of temperature and chemical potentials.

Transparent conducting electrodes (TCE) consisting of silver nanowires (SNW) with a single-layer graphene (SLG) cover demonstrate higher optical transparency and lower sheet resistance than indium tin oxide (ITO) and are comparable to the best reported results in TCEs. SNW layer is simulated using the spectral averaging of the FDTD transmittance data from indiscriminately selected frames. Simulations are done for a number of frames until a convergent set of averaged spectra is obtained. SLG layer is simulated separately and contributes to the total transmittance as a multiplicative constant.

Metasurfaces based on sub-wavelength patterning have major potential for realizing arbitrary control of the wavefront of the diffracted light by achieving local control of the phase amplitude and polarization. We discuss novel devices based on this technique; a salient feature is the ability to create often with a single digital mask an arbitrary analog phase profile. A variety of flat optical components, including lenses, polarizers, vortex plates, coatings, holograms and couplers with polarization invariant coupling efficiency will be presented.

We study the radiative decay and Purcell effect for finite-size electric and magnetic dipole emitters placed in an uniaxial medium. For both electric and magnetic dipoles, we find that the radiative rate is strongly enhanced in the hyperbolic regime, when the signs of the longitudinal and transverse dielectric constants are opposite. However, the behavior of the Purcell factor in the transition region from elliptic to hyperbolic regimes is very different for the electric and magnetic dipoles. The Purcell factor enhancement for magnetic dipole is weaker and it takes place only deep inside the hyperbolic regime, while for electric dipole the maximum enhancement is achieved at the transition boundary.

The spectral behaviors of an externally-illuminated thermal infrared metamaterial were characterized through simulation and experimental measurement of the power transmittance and reflectance within the 6 - 20μm range. Finite-difference time domain (FDTD) simulations in both 2-D and 3-D environments were swept over a multitude of bent dipole inclusion configurations at normal incidence angles to produce a model which exhibited a dominant electrical resonance in the long-wave infrared (IR) and increased in magnitude, bandwidth and wavelength as a function of the dipole length. Despite the appearance of fabrication defects in the measured samples, it was found the experimental data was in good agreement with the 3-D FDTD simulations, though not at all with the 2-D simulations. These introductory results indicate the dipole inclusion may behave in many ways similar to an antenna in the IR, enabling spectrally- and spatially-selective control of the emission pattern.

We design, fabricate, and characterize a Frequency Selective Surface (FSS) with directional thermal emission and absorption for long-wave infrared wavelengths (LWIR). The FSS consists of an array of patch antennas connected by microstrips, the ensemble of which supports leaky-wave type modes with forward and backward propagating branches. The branches are designed to intersect at 9.8 μm, and have a broadside beam with 20° FWHM at this wavelength. The absorption along these branches is near-unity. Measurement of the hemispherical directional reflectometer (HDR) shows good agreement with simulation. The ability to control the spectral and directional emittance/absortpance profiles of surfaces has significant applications for radiation heat transfer and sensing.

The multiplex-bands absorption of sandwich-structure metamaterials based metal- dielectric- metal scheme are investigated numerically and experimentally. The optical properties of cross-shape antenna perfect absorber metamaterials are demonstrated in mid-IR electromagnetic (EM) wave. The dual-band perfect absorber with polarization independence is observed under normal incidence. In order to understand the EM properties of dual-band perfect absorber, the plasmonic excitation and the induced current distribution were clarified for both peaks. The simulation results clearly show that the absorption bands are independently governed by the size of each part of the patterned nanostructure. The repositioning of two near-perfect absorption peaks possesses a linear relationship. This allows for a flexible reconfigurability over the entire near-infrared regime. Furthermore, in order to obtain multiplex-bands spectral absorption response, two cross-shape antennas are connected to form one dumbbell antenna. The three perfect-absorption peaks can be controlled by the individual dipole antenna elements in the conditions of polarization incident EM wave.

Recently we have demonstrated membrane projection lithography (MPL) as a fabrication approach capable of creating 3D structures with sub-micron metallic inclusions for use in metamaterial and plasmonic applications using polymer material systems. While polymers provide several advantages in processing, they are soft and subject to stress-induced buckling. Furthermore, in next generation active photonic structures, integration of photonic components with CMOS electronics is desirable. While the MPL process flow is conceptually simple, it requires matrix, membrane and backfill materials with orthogonal processing deposition/removal chemistries. By transitioning the MPL process flow into an entirely inorganic material set based around silicon and standard CMOS-compatible materials, several elements of silicon microelectronics can be integrated into photonic devices at the unit-cell scale. This paper will present detailed fabrication and characterization data of these materials, emphasizing the processing trade space as well as optical characterization of the resulting structures.

When an applied magnetic field has an arbitrary direction with respect to the lattice axes of a periodically microstructured or nanostructured metamaterial, the effective permittivity tensor of the metamaterial sample becomes anisotropic and all its components can be nonzero. This is true even if the microstructure has a high symmetry, e.g., cubic or triangular. It is found that the strong magneto-induced anisotropy which appears in the macroscopic response leads to unusual anisotropic behavior of the Voigt effect and other magneto-optical (MO) effects. I.e., these phenomena become strongly dependent on the direction of the applied static magnetic field, as well as on the direction of the time dependent electromagnetic field, with respect to the symmetry axes of the periodic microstructure.

Quantum-mechanical theory of the plasmon nanoresonator laser is presented. The Hamiltonian equations of motion are obtained for the plasmon field in the time domain. Then the plasmon field is quantized to develop the quantum plasmonics (QP). QP equations are solved and dynamics of the plasmon laser is obtained. We show that the plasmon laser is essentially thresholdless device in the nanosize limit, which radiation is coherent regardless of the pumping rate. We obtain the statistics of quanta, intensity, spectrum and linewidth of the radiation. Theory can also be applied to the usual photonic microlasers, metal-dielectric lasers and other small cavity devices.

A well-known challenge for fabricating metamaterials is to make unit cells significantly smaller than the operating wavelength of light, so one can be sure that effective-medium theories apply. But do they apply? Here we show that nonlocal response in the metal constituents of the metamaterial leads to modified effective parameters for strongly subwavelength unit cells. For infinite hyperbolic metamaterials, nonlocal response gives a very large finite upper bound to the optical density of states that otherwise would diverge. Moreover, for finite hyperbolic metamaterials we show that nonlocal response affects their operation as superlenses, and interestingly that sometimes nonlocal theory predicts the better imaging. Finally, we discuss how to describe metamaterials effectively in quantum optics. Media with loss or gain have associated quantum noise, and the question is whether the effective index is enough to describe this quantum noise effectively. We show that this is true for passive metamaterials, but not for metamaterials where loss is compensated by linear gain. For such loss-compensated metamaterials we present a quantum optical effective medium theory with an effective noise photon distribution as an additional parameter. Interestingly, we find that at the operating frequency, metamaterials with the same effective index but with different amounts of loss compensation can be told apart in quantum optics.

A mechanism based on two-wave mixing to dramatically reduce optical losses in non-ohmic conductors is proposed. The losses in the probe mode are compensated due to the flow of energy from the support mode. The effect is derived from the solution of non-linear Maxwell’s equations combined with coherence conditions for two parametrically coupled waves. We provide a case which shows that this scheme can be realized experimentally in bulk semiconductors, e.g. zinc telluride (ZnTe), within the mid-IR frequency range.

Transparent conducting oxides (TCO) are an interesting class of plasmonic materials, which are under intensive study for their use in low-loss metamaterials and a range of applications such as sensing, imaging and transformation optics. Here, using both full-wave simulations and an equivalent circuit model for pairs of nanoparticles of aluminum doped zinc oxide (AZO), we study the plasmonic effects for low loss low index metamaterials for infrared applications. The behavior of localized surface plasmon resonances (LSPR) of AZO nanoparticle dimers embedded in a host polymer medium is investigated for different dimer orientations with respect to the indicent electromagnetic wave. In doing this, the role of dressed polarizability to enhance and quench the plasmonic effects is also considered. The effects of the nanoparticles relative size and the spacing between them are studied. Understanding these resonances and their dependence on dimer orientations, provides a means to design metamaterial structures for use in the near infrared (NIR) region with epsilon-near-zero properties leading also to low index metamaterials. In our studies, we demonstrate how nanospheres with radii less than 100 nm that are distributed with an average spacing less than their diameter, can result in an effective medium with refractive index less than one. We utilize a full-wave frequency domain finite element method in conjunction with an equivalent-circuit model for the nanoscale dimers in order to describe the spectral response of the bulk low index properties. We also present a statistical analysis to obtain the effective refractive index for incident light having different polarizations.

We present a novel design of a subwavelength modified bow-tie antenna that is capable of generating strong broadband field enhancement in its extended feed gap. This modified bow-tie antenna is comprised of a conventional bow-tie antenna with capacitive extended bars attached to the apex points of the bow-tie. The feed gap between the two capacitive bars is separated with a deep subwavelength width for the generation of enhanced local electrical field. Threedimensional finite element method model is utilized to systematically explore the properties of this antenna design. Through adjusting the bow-tie geometry and the substrate properties, the antenna structure is optimized with a central resonant frequency at 100 GHz. Highly enhanced electrical field is created between the extended bar under radio frequency (RF) illumination. With the optimized design, numerical simulations show that a uniform field enhancement of more than 200 through the entire feed gap with a bandwidth of 40 GHz can be achieved. The strongly enhanced RF field within the gap can be applied to directly modulate guided optical wave propagating in a waveguide embedded in the substrate underneath the feed gap. This work builds up a bridge between devices in the RF and optical frequency regimes that may find many potential applications in RF photonic devices and systems.

Metamaterial research is an extremely important global activity that promises to change our lives in many different ways, including making objects invisible and having a very dramatic impact upon the energy and medical sectors of society. Behind all of the applications, however, lies the design of metamaterials and this can be led by elegant routes that include nonlinearity, waveguide complexity and structured light. The associated optical device formats often involve coupling to soliton behavior. Vortex formation is going to be a critical feature for future applications focusing attention upon the role of angular momentum in special metamaterial-driven light beams. In this context nonlinear diffraction must be assessed and some discussion of a magnetooptical environment will be included. Solitonic behavior of light beams will be mentioned, including what have now become known as Peregrine solitons.

The study of optical nanoantennas is a rapidly developing area of optics and nanophotonics. Nowdays, the most popular type of nanoantennas is a plasmonic one made of metallic elements. However, plasmonic nanoantennas have large dissipative losses. Here we present an overview of the recent results of a newly emerged field of all-dielectric optical nanoantennas. These optical nanoantennas are made of high-permittivity low-loss dielectric particles. Moreover, in addition to the electric resonances such nanoscale particles exhibit very strong magnetic response in the visible range. We introduce and study a highly efficient Huygens element and Yagi-Uda type nanoantennas based on dielectric nanoparticles. We also introduce a novel concept of all-dielectric superdirective nanoantennas based on the generation of higher-order optically-induced magnetic multipole modes. For such superdirective dielectric nanoantennas, we predict the effect of beam steering at the nanoscale characterized by a subwavelength sensitivity of the beam radiation direction to the source position. Based on all these new properties, optical nanoantennas offer unique opportunities for applications such as optical communications, photovoltaics, non-classical light emission, and sensing.

The transition between the long-wavelength and the short-wavelength regimes of light propagation in all-dielectric metamaterials is experimentally probed using a hyperspectral near-field scanning microscope technique. Our measurements lead to an invariant quantity “λ/n” of only 1.78 times the dielectric lattice period as the criterion for the possible application of homogenization theories.

By optimizing the shape and scale of perforations as well as the depth of different layers, we obtained a metal- dielectric-metal double fishnet metamaterial with an unbroken 38-nm bandwidth of negative refractive index in visible spectrum, spaning from 459 to 497 nm. Moreover, the real parts of permittivity and permeability of this metamaterial are simultaneously negative from 460 to 478 nm in wavelength, reaching a frequency band as high as to the blue region - a territory that has never been explored before in visible spectrum.

In this paper, we rotate an array of asymmetrical double layer of 4-strips windmill structure to investigate its effect on the chirality and sensitivity detection of biomolecular structures. The structure is made up of silver material with 300nm pitch and 10nm separation between layers. The spectrum shows two resonance modes on 600THz and 900THz with linear polarized light normally incident on the structure. We investigate the CD by rotating one of the layers with respect to the horizontal axis of the other layer by the angle θ. It is observed that the CD spectra at different angles are different. The rotation resulted in larger wavelength shift of the CD spectra. In addition, the CD also increases with the rotating angle given a larger absorption difference between the left and right handed circular polarized light.

We investigate the possibility of achieving the scattering cancellation cloaking at different frequencies with a single shell composed of multiple plasmonic constituents simultaneously, without increasing the physical size of the whole system. Our theory results based on the Mie scattering theory show that the number of cloaking frequencies can be increased by adding extra plasmonic constituents, which are further verified by simulating electromagnetic propagation with finite element method. A special design has also been proposed, showing its great feasibility in the practical application.

In this paper the formulas from the dispersion equation for the infinite photonic crystal for exact definition of frequencies of gap location, gap edges and gap width with multiple optical layers lengths in bilayer cell in the frequency range from 0.1 to 1 THz were derived. The formulas were verified by numerical simulation of photonic crystals using the transmission matrix method and finite-difference time-domain method for the first, second and third multiplicity of optical layers lengths in bilayer cell of the photonic crystal. The formulas for the second multiplicity case were confirmed experimentally.

Efficient engineering of metamaterials involves modeling of electric field profiles around these structures. Realistic modeling of the electric field in metamaterials requires accurate knowledge of optical constants of the compo- nents for which traditionally the bulk values are taken. Further progress in the developing of metamaterials is characterized by a reduction of the pattern size, dimensions of single layers in multilayered structures etc. It has been understood that optical functions in low-dimensional and nano-sized materials substantially differ from their bulk values increasingly affecting by quantum processes. In this work we develop a complex method for analytical modeling of electric field profiles in metamaterials including quantum processes in nano-sized multi-layered structures. In particular based on first principles density functional theory we obtained simple analytical functions allowing predictions the optical functions variations with the size reduction of single metamaterial components over a wide spectral region. It is shown that optical functions of nano-sized films substantially (by 50 percent and more) differ from those in bulk. The new calculated optical functions of the components are used for electric field profile modeling of nano-sized multilayered structures by nonlocal Green function technique including effects of spatial dispersion. Silicon, silicon dioxide, and water layers are used as an example. The method effectively incorporates real atomic structure reconstruction on surfaces and inner interfaces thus providing with a more realistic picture for modeling. By comparison with experiment it is demonstrated that our method predicts image potential of the nanostructures in better agreement with experiment than if using traditional classic electrodynamics approach neglecting the quantum effects. The results are discussed in comparison with literature.

In this paper we study the influence of the period between U-shaped split-ring resonators (SRRs) on the trans- mission/absorbtion properties and refraction index of metasurfaces in THz frequency range (0.1 - 1 THz) using experiments and numerical simulations. The metasurfaces are formed by U-shaped SRRs arrays. The period varies from 63 to 300 μm The metasurface electromagnetic responses are obtained using terahertz time-domain spectroscopy. The experimental and numerical results reveal the shift in transmission spectra for the metasurface response and the tuning of absorbtion intensity at the period between U-shaped SRRs changing. The notable change in the metasurface refractive index is shown.