This PDF file contains the front matter associated with SPIE Proceedings Volume 9125, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Here we show the way to easily tune and engineer the optical response of hybrid structures composed by self ordered dielectric nanospheres partially covered by anisotropic plasmonic structures. The overall structure is a hybrid plasmonic-photonics nanostructure acting as a meta-surface witch morphology allows efficient and versatile light manipulation both for linear polarized and circular polarized fields in the visible and near infrared frequencies.

Gyroid is a type of three-dimensional chiral structures, which have attracted much research attention recently. A dielectric single gyroid (SG) can be a candidate for providing new means of guiding light because it has been shown to exhibit complete photonic band gaps. Owing to the chiral nature, the SG metamaterials may exhibit circular polarization-dependent properties, leading to new types of polarization-sensitive devices. In this work, we present studies based on finite-difference time-domain (FDTD) method for analyzing the polarization-dependent characteristics of dielectric SG. We show that the operation frequency of SG metamaterials can be advanced from microwave to visible region by varying its material, lattice constant and volume fraction. The corresponding band structures, transmission spectra for right circularly polarized (RCP) light and left circularly polarized (LCP) light, and circular dichroism (CD) indices are examined. According to our analysis, a circular polarization gap is found in the visible region. In particular, the correlation between the volume fraction of dielectric SG and the frequency range of circular polarization band gaps is also investigated. These results are crucial for the design of functional polarization-sensitive devices at the visible wavelength based on dielectric single gyroid metamaterials.

The present work investigates the propagation properties of the surface plasmon polariton wave supported on graphene surface over an anisotropic substrate at far-infrared frequencies. Initially, the surface wave’s propagation on isotropic media substrate is studied and verified with the theoretical estimation, including the noteworthy epsilon-near-zero case. Moreover, after utilizing theoretical substrate media and examining anisotropy relative to the normal to graphene’s surface, direction, the anisotropy is enforced to the tangential direction revealing the significant influence of the substrate on the surface wave that is propagating on graphene. Additionally, the more realistic implementation with graphene’s substrate consisting of metamaterial resonators is thoroughly investigated. Numerical results are extracted through a reliable finite-difference time-domain (FDTD) algorithm, focalising, mainly, on the wavelength of graphene’s surface wave.

The interaction between light and matter involves not only an energy transfer, but also the transfer of linear momentum. In everyday life applications this linear momentum of light is too small to play any significant role. However, in nanoscale dimensions, the associated optical forces start to play an increasingly important role. These forces are, e.g., large enough for exiting experiments in the fields of cavity-optomechanics, laser cooling and optical trapping of small particles. Recently, it has been suggested that optical gradient forces can also be employed for all-optical actuation in micro- and nanophotonic systems. The typical setup consists of two slab waveguides positioned in each others vicinity such that they are coupled through the interaction of the evanescent tails. Although the gradient forces between these waveguides can be enhanced considerably using electromagnetic resonators or slow-light techniques, the resulting displacements remain relatively small. In this contribution, we present an alternative approach to enhance optical gradient forces between waveguides using a combination of transformation optics and metamaterials. Our design starts from the observation that gradient forces exponentially decay with the separation distance between the waveguides. Therefore, we employ transformation optics to annihilate the apparent distance for light between the waveguides. Analytical calculations confirm that the resulting forces indeed increase when such an annihilating cladding is inserted. Subsequently, we discuss the metamaterial implementation of this annihilating medium. Such lensing media automatically translate into anisotropic metamaterials with negative components in the permittivity and permeability tensors. Our full-wave numerical simulations show that the overall amplification is highly limited by the loss-tangent of the metamaterial cladding. However, as this cladding only needs to operate in the near-field for a specific polarization, we can also consider single-negative metamaterial implementations. We finally demonstrate that in this way metamaterials can support optical forces enhanced by more than 200 times [Phys. Rev. Lett. 110, 057401 (2013)].

Photoelectric properties of metamaterials comprising asymmetrically shaped, similarly oriented metallic nanoparticles embedded in a homogeneous semiconductor matrix are theoretically and numerically studied. The asymmetric shape of the nanoparticles is found to result in the existence of a preferred direction where “hot” photoelectrons are emitted from the nanoparticle surface under the action of the localized plasmonic resonance excited in the nanoparticles. The resulting directional photocurrent flow occurring when nanoparticles are uniformly illuminated by a homogeneous plane wave is the direct analogy of the photogalvanic effect known to exist in naturally occurring non-centrosymmetric media. This plasmonic bulk photovoltaic effect is intermediate between the inner photoelectric effect in bulk media and the outer photoelectric effect at macroscopic interfaces. The results obtained are valuable for characterizing photoemission and photoconductive properties of plasmonic nanostructures. They can find many uses for photodetection-related and photovoltaic applications.

An efficient methodology for the modification of electrical resonators in order to be readily applicable at the terahertz regime is developed in this paper. To this aim, the proposed miniaturization technique starts from the conventional resonator which, without any change, exhibits the lowest possible electrical resonance for minimum dimensions. Subsequently, a set of interdigital capacitors is embedded in the original structure to increase capaci- tance, while their impact on the main resonance is investigated through computational simulations. Furthermore, to augment the inductance of the initial resonator, and, hence reduce the resonance frequency, the concept of spiral inductor elements is introduced. Again, results for the featured configuration with the additional elements are numerically obtained and all effects due to their presence are carefully examined. Finally, the new alterations are combined together and their in influence on the resonance position and quality is thoroughly studied.

We report on measurements of optical, morphological and electrical properties of silver nanolayers. The Ag films of thickness from 10 to 500 nm are deposited in e-beam evaporator. Fused silica and sapphire substrates are used with nominal root-mean-square (RMS) roughness equal 0.3 and 0.2 nm, respectively. Silver is deposited either directly on substrates or on Ge, Ni, or Ti wetting interlayer. The refractive index n and the extinction coefficient κ of Ag films are derived from spectroscopic ellipsometry and reflectance measurements carried in air in the spectral range from 0.6 to 6.5 eV (2200 – 193 nm) using a rotating analyzer ellipsometer (V-VASE, J.A. Woollam Co.). Surface roughness is measured using AFM (Ntegra NT-MDT) under tapping mode in air with sharp etalon probes and 5:1 aspect ratio. Ag layers of 10 and 30 nm thickness have nearly the same RMS roughness when deposited at temperatures from 180 to 350 K. The lowest RMS=0.2 nm is achieved for 10 nm film Ag/Ge evaporated at 295 K. The sheet resistance of the Ag films is measured using two methods: the van der Pauw method with the electrical contacts located on perimeters of the samples and four probes contacting the samples at points lying in a straight line. Specific resistivity of Ag films on fused silica change from <10⁹ to 1.80 [μΩ∙cm] when thickness increases from 10 to 500 nm. Specific resistivity of 10, 30 and 50 nm thick Ag films on 1 nm Ge wetting layer are equal 14.01, 7.89, and 5.58 [μΩ∙cm], respectively, and are about twice higher than those of Ag films on Ti or Ni interlayers.

Since their inception, metamaterial fishnet structures have frequently been used to exhibit a negative refractive index. Their shape and structure make it possible to independently produce both a negative permeability (μ) and a negative permittivity (ε). Fishnets that display this characteristic can be referred to as a double negative metamaterial. Although other techniques have been demonstrated, fishnets are commonly fabricated using electron-beam lithography (EBL) or focused ion-beam (FIB) milling. In this paper we demonstrate the fabrication of fishnets using nano-imprint lithography (NIL). Advantages associated with NIL include a shorter fabrication time, a larger feasible pattern area and reduced costs. In addition to these advantages, the quality of the fabricated structures is excellent. We imprint a stamp directly into a metal-dielectric-metal stack which creates the fishnet and, as an artifact of the technique, a periodic array of nanopillars. Two different designs of the fishnet and nanopillar structure have been fabricated and optical measurements have been taken from both. In addition to the experimental measurements the structures have also been extensively simulated, suggesting a negative refractive index with a real part as large in magnitude as five can be achieved.

The evaluation of electromagnetic material parameters from metamaterial structures has received much attention in the literature. Among others, one method is to retrieve the material parameters from the reflection and transmission measurements of the sample material. It has been found that the electromagnetic material parameters depend on the angle of incidence. Although based on the Nicholson-Ross-Weir technique, the proposed extraction technique has no limitations on the angle of incidence. The proposed extension of the NRW extraction technique is used to study a fishnet structure fabricated by nanoimprint lithography. Silver (Ag)- Magnesium Fluoride (MgF₂) - silver (Ag) was deposited on the thick PMMA layer before directly imprinted by a stamp. The effective material parameters have been found to characterise the imprinted fishnet structure.

The main goal of our research was to investigate the optical properties of nanocomposites, created by combining titanium dioxide with noble metals. Our research was focused on silver Ag, which reveals strong plasmonic effects in the visible spectrum, and rutile TiO₂ - a commonly used semiconductor material that does not present any significant optical properties in the mentioned range of electromagnetic waves. Our results show that when coating is considered (i.e. the TiO₂ particle is covered by an additional Ag layer) the position of the extinction peak can be manipulated and shifted towards lower wavelengths. However, when the main TiO₂ particle is surrounded by small Ag spheres, such extinction peak occurs at a fixed wavelength only and cannot be adjusted.

In optical metamaterials, the scatterers are usually aligned symmetrically with respect to the unit cells of the material. In this work, we consider metamaterials in which the "metamolecules" can be non-centrosymmetric and have an arbitrary, but common, orientation in the unit cells. Such internally twisted crystalline structures are difficult to find in natural materials, but metamaterials of this type can be designed and fabricated at will. Here we present a theoretical method that enables a detailed analysis of internally twisted non-centrosymmetric metamaterials. The method establishes a connection between the optical properties of a metamaterial and the plane-wave optical response of a single two-dimensional array of metamolecules. In this theory, the effective wave parameters, such as the refractive index and wave impedance, are retrieved. Using the model, we show that these parameters can dramatically depend on the wave propagation direction and metamolecular orientation in a metamaterial. This dependence provides a possibility to adjust and control the plane-wave content of optical beams propagating in the material.

We theoretically investigate general existence conditions for broadband bulk large-wavevector (high-k) propagating waves (such as volume plasmon polaritons in hyperbolic metamaterials) in arbitrary subwavelength periodic multilayers structures. Treating the elementary excitation in the unit cell of the structure as a generalized resonance pole of reflection coefficient and using Bloch’s theorem, we derive analytical expressions for the band of large-wavevector propagating solutions. We apply our formalism to determine the high-k band existence in two important cases: the well-known metaldielectric and recently introduced graphene-dielectric stacks. We confirm that short-range surface plasmons in thin metal layers can give rise to hyperbolic metamaterial properties and demonstrate that long-range surface plasmons cannot. We also show that graphene-dielectricmultilayers tend to support high-k waves and explore the range of parameters, where this is possible, confirming the prospects of using graphene for materials with hyperbolic dispersion. The suggested formalism is applicable to a large variety of structures, such as continuous or structured microwave, terahertz (THz) and optical metamaterials, optical waveguide arrays, 2D plasmonic and acoustic metamaterials.

Recent advances have seen asymmetric split ring resonators (A-SRRs) developed as sensing elements to record a shift in their peaks when there is a corresponding change in the surrounding environment. These studies have led to the investigation of Fano resonances associated with the coupling of the resonances of the A-SRRs with the molecular resonances of the analyte. The hormone estradiol (E2) was dissolved in ethanol and evaporated, leaving thickness of a few hundreds of nanometres on top of gold A-SRRs on a silica substrate. The reflectance was measured and a red shift is recorded from the resonators plasmonic peaks. The geometric sizes of the ASRRs are calculated to tune the plasmonic resonances near the molecular resonance of the C-H stretch at nominally 3.33 microns. Corresponding Lumerical modelling of the experimental data is performed using only the intensity and wavelength to match the Fano resonance at modified wavelengths of 3.42 and 3.49 microns.