A Controllable Plasmonic Resonance in a SiC-Loaded Single-Polarization Single-Mode Photonic Crystal Fiber Enables Its Application as a Compact LWIR Environmental Sensor.

Near-perfect resonant absorption is attained in a single-polarization single-mode photonic crystal fiber (SPSM PCF) within the long-wave infrared (LWIR) range from 10 to 11 μm. The basic PCF design is a triangular lattice-based cladding of circular air holes and a core region augmented with rectangular slots. A particular set of air holes surrounding the core is partially filled with SiC, which exhibits epsilon near-zero (ENZ) and epsilon negative (ENG) properties within the wavelength range of interest.

A Terahertz (THz) Single-Polarization-Single-Mode (SPSM) Photonic Crystal Fiber (PCF).

This paper presents a novel approach to attain a single-polarization-single-mode (SPSM) photonic crystal fiber (PCF) in the terahertz (THz) regime. An initial circular hole PCF design is modified by introducing asymmetry in the first ring of six air holes in the cladding, i.e.

Wirelessly Powered Light and Temperature Sensors Facilitated by Electrically Small Omnidirectional and Huygens Dipole Antennas.

Wirelessly powered, very compact sensors are highly attractive for many emerging Internet-of-things (IoT) applications; they eliminate the need for on-board short-life and bulky batteries. In this study, two electrically small rectenna-based wirelessly powered light and temperature sensors were developed that operate at 915 MHz in the 902-928-MHz industrial, scientific, and medical (ISM) bands. First, a metamaterial-inspired near-field resonant parasitic (NFRP) Egyptian axe dipole (EAD) antenna was seamlessly integrated with a highly efficient sensor-augmented rectifier without any matching network.

Erratum: Highly Subwavelength, Superdirective Cylindrical Nanoantenna [Phys. Rev. Lett. 120, 237401 (2018)].

This corrects the article DOI: 10.1103/PhysRevLett.120.

Circular hole ENZ photonic crystal fibers exhibit high birefringence.

-A novel photonic crystal fiber (PCF) design that yields very high birefringence is proposed and analyzed. Its significantly enhanced birefringence is achieved by filling selected air holes in the cladding with an epsilon-near-zero (ENZ) material. Extensive simulation results of this asymmetric material distribution in the lower THz range demonstrate that the reported PCF has a birefringence above 0.

Highly Subwavelength, Superdirective Cylindrical Nanoantenna.

A superdirective cylindrical nanoantenna is demonstrated with a multilayered cylindrical metamaterial-inspired structure. Targeting specific scattering coefficients for the dipole and higher-order modes, the ideal limit of needle radiation is demonstrated. A five-layer system is optimized to demonstrate its approach to the theoretical directivity bound.

Realization of an Ultra-thin Metasurface to Facilitate Wide Bandwidth, Wide Angle Beam Scanning.

A wide bandwidth, ultra-thin, metasurface is reported that facilitates wide angle beam scanning. Each unit cell of the metasurface contains a multi-resonant, strongly-coupled unequal arm Jerusalem cross element. This element consists of two bent-arm, orthogonal, capacitively loaded strips.

Superbackscattering nanoparticle dimers.

The theory and design of superbackscattering nanoparticle dimers are presented. We analytically derive the optimal configurations and the upper bound of their backscattering cross-sections. In particular, it is demonstrated that electrically small nanoparticle dimers can enhance the backscattering by a factor of 6.

Magnetic dipole super-resonances and their impact on mechanical forces at optical frequencies.

Artificial magnetism enables various transformative optical phenomena, including negative refraction, Fano resonances, and unconventional nanoantennas, beamshapers, polarization transformers and perfect absorbers, and enriches the collection of electromagnetic field control mechanisms at optical frequencies. We demonstrate that it is possible to excite a magnetic dipole super-resonance at optical frequencies by coating a silicon nanoparticle with a shell impregnated with active material. The resulting response is several orders of magnitude stronger than that generated by bare silicon nanoparticles and is comparable to electric dipole super-resonances excited in spaser-based nanolasers.

Size-dependent permittivity and intrinsic optical anisotropy of nanometric gold thin films: a density functional theory study.

Physical properties of materials are known to be different from the bulk at the nanometer scale. In this context, the dependence of optical properties of nanometric gold thin films with respect to film thickness is studied using density functional theory (DFT). We find that the in-plane plasma frequency of the gold thin film decreases with decreasing thickness and that the optical permittivity tensor is highly anisotropic as well as thickness dependent.

Impact of the excitation source and plasmonic material on cylindrical active coated nano-particles.

Electromagnetic properties of cylindrical active coated nano-particles comprised of a silica nano-cylinder core layered with a plasmonic concentric nano-shell are investigated for potential nano-sensor applications. Particular attention is devoted to the near-field properties of these particles, as well as to their far-field radiation characteristics, in the presence of an electric or a magnetic line source. A constant frequency canonical gain model is used to account for the gain introduced in the dielectric part of the nano-particle, whereas three different plasmonic materials (silver, gold, and copper) are employed and compared for the nano-shell layers.

CNP optical metamaterials.

Simulation results for optical metamaterials (MTMs) derived from active coated nano-particle (CNP) inclusions for operation in the visible range of the spectrum between 400nm and 700nm are presented. Several examples of optical MTMs designed with these inclusions are characterized, including two-dimensional (2D) CNP metafilms; three-dimensional (3D) periodic CNP arrays; and 3D random CNP distributions. The properties of these optical MTMs are explored using effective medium theories that are applicable to these inclusion configurations.

Investigating functionalized active coated nanoparticles for use in nano-sensing applications.

In this paper we investigate the use of active coated nanoparticles (CNPs) for nano-sensing applications. Simulation results of the optical properties of an active CNP with a 24nm radius active silica core and 6nm thick plasmonic shell made of silver that has been functionalized by an additional spherical outer layer of varying thickness and refractive index are presented. In particular, the effects of the functional-layer thickness and refractive index on the super-resonant (SR) state of the active CNP are presented.

The design and simulated performance of a coated nano-particle laser.

The optical properties of a concentric nanometer-sized spherical shell comprised of an (active) 3-level gain medium core and a surrounding plasmonic metal shell are investigated. Current research in optical metamaterials has demonstrated that including lossless plasmonic materials to achieve a negative permittivity in a nano-sized coated spherical particle can lead to novel optical properties such as resonant scattering as well as transparency or invisibility. However, in practice, plasmonic materials have high losses at optical frequencies.

Finite-difference time-domain analysis of the tunneling and growing exponential in a pair of epsilon-negative and mu-negative slabs.

Pairing together planar material slabs with opposite signs for the real parts of their constitutive parameters has been shown to lead in the steady-state regime to interesting and unconventional properties that are not otherwise observable for single slabs, such as resonance, anomalous tunneling, transparency, and subwavelength imaging through the reconstruction of evanescent waves [A. Alù and N. Engheta, IEEE Trans.

Reciprocity between the effects of resonant scattering and enhanced radiated power by electrically small antennas in the presence of nested metamaterial shells.

Reciprocity between the power scattered by nested metamaterial shells and the power radiated by an antenna centered within those nested shells has been investigated. Resonant scattering caused by an incident, fundamental transverse-magnetic mode was found to be reciprocal to the power resonantly radiated by an electrically small electric dipole for a variety of configurations. These findings indicate that the power radiated by an electrically small antenna and scattered by an electrically small object can be significantly increased through the use of realizable metamaterials.

Time-to-Collision estimation from motion based on primate visual processing.

A population coded algorithm, built on established models of motion processing in the primate visual system, computes the time-to-collision of a mobile robot to real-world environmental objects from video imagery. A set of four transformations starts with motion energy, a spatiotemporal frequency based computation of motion features. The following processing stages extract image velocity features similar to, but distinct from, optic flow; "translation" features, which account for velocity errors including those resulting from the aperture problem; and finally, estimate the time-to-collision.

Propagation in and scattering from a matched metamaterial having a zero index of refraction.

Planar metamaterials that exhibit a zero index of refraction have been realized experimentally by several research groups. Their existence stimulated the present investigation, which details the properties of a passive, dispersive metamaterial that is matched to free space and has an index of refraction equal to zero. Thus, unlike previous zero-index investigations, both the permittivity and permeability are zero here at a specified frequency.

Causality and double-negative metamaterials.

The causality of waves propagating in a double-negative (DNG) metamaterial (epsilon (r)<0 and mu(r)<0) has been investigated both analytically and numerically. By considering the one-dimensional electromagnetic problem of a pulsed current sheet radiating into a DNG medium, it is shown that causality is maintained in the presence of a negative index of refraction only if the DNG medium is dispersive. A Drude model DNG medium is used in this study.

Existence and design of trans-vacuum-speed metamaterials.

The existence of passive metamaterials, in which the speed of light is greater than its speed in vacuum, is proposed. Analysis and numerical simulations demonstrate these trans-vacuum-speed (TVS) properties. A transmission line realization of a TVS medium is established.