Simone Tricarico

Plasmonic Metamaterial Cloaking at Optical Frequencies

In this paper, we present the design of cylindrical and spherical electromagnetic cloaks working at visible frequencies. The cloak design is based on the employment of layered structures consisting of alternating plasmonic and nonplasmonic materials, and exhibiting the collective behavior of an effective epsilon-near-zero material at optical frequencies. The design of a cylindrical cloak to hide cylindrical objects is first presented. Two alternative layouts are proposed, and both magnetic and nonmagnetic objects are considered. Then, the design of spherical cloaks is also presented. The full-wave simulations presented throughout the paper confirm the validity of the proposed setup, and show how this technique can be used to reduce the observability of cylindrical and spherical objects. The effect of the losses is also considered.

Electromagnetic cloaking devices for TE and TM polarizations

In this paper, we present the design of an electromagnetic cloaking device working for both transverse electric (TE) and transverse magnetic (TM) polarizations. The theoretical approach to cloaking used here is inspired by the one presented by Al??and Engheta (2005 Phys. Rev. E 72 016623) for TM polarization. The case of TE polarization is firstly considered and, then, an actual inclusion-based cloak for TE polarization is also designed. In such a case, the cloak is made of a mu-near-zero (MNZ) metamaterial, as the dual counterpart of the epsilon-near-zero (ENZ) material that can be used for purely dielectric objects. The operation and the robustness of the cloaking device for the TE polarization is deeply investigated through a complete set of full-wave numerical simulations. Finally, the design and an application of a cloak operating for both TE and TM polarizations employing both magnetic inclusions and the parallel plate medium already used by Silveirinha et al (Phys. Rev. E 75 036603) are presented.

Cloaking apertureless near-field scanning optical microscopy tips.

We numerically demonstrate that properly designed plasmonic covers can be used to enhance the performance of near-field scanning optical microscopy (NSOM) systems based on the employment of apertureless metallic tip probes. The covering material, exhibiting a near-zero value of the real permittivity at the working frequency, is designed in such a way to dramatically reduce the undesired scattering due to the strongly plasmonic behavior of the tip. Though the light scattering by the tip end is necessary for the correct operation of NSOMs, the additional scattering due to the whole probe affects the signal-to-noise ratio and thus the resolution of the acquired image. By covering the whole probe but not the very tip, we show that unwanted scattering can be effectively reduced. A realistic setup, working at mid-IR frequencies and employing silicon carbide covers, has been designed and simulated to confirm the effectiveness of the proposed approach.

Achieving PMC boundary conditions through metamaterials

Purpose – The purpose of this paper is to show how metamaterials with extreme values of permittivity and permeability, may be effectively used to design artificial magnetic conductors (AMC) at a given frequency. In particular, this paper theoretically determines, for the different polarizations of the incidence field, the conditions under which metamaterials can behave as an AMC. Design/methodology/approach – In order to find out the required values of the constitutive parameters, this paper has done a theoretical analysis based on the transmission-line theory. The obtained analytical reflection coefficient has been particularized for the different possible polarizations of the incidence field in order to find the constitutive parameters values that this paper needs for the AMC behavior. Findings – Depending on the polarization of the field, it is shown that different values of the constitutive parameters are needed to get AMCs. In particular, it is shown that in the case of TEM and TE polarizations, a la...

Resonating Plasmonic Particles to Achieve Power Transmission Enhancement Through Subwavelength Apertures

In this letter, we propose a resonant approach to achieve enhanced power transmission through electrically small apertures in the near-infrared. The enhancement is obtained by exciting a magnetic resonance in a pair of plasmonic pillars, placed on a screen with a drilled subwavelength hole. The localized resonance allows us to enhance the equivalent magnetic dipole moment of the aperture, hence increasing the transmitted power. The proposed setup may find interesting applications in high-capacity memories, ultradiffractive imaging systems, high-resolution spatial filters, and high-precision lithography.

Miniaturization and Characterization of Metamaterial Resonant Particles

This paper is focussed on the miniaturization and characterization of semi-lumped resonators, of interest for the synthesis of metamaterial-based structures such as metamaterial transmission lines, frequency selective surfaces, absorbers, and radiating elements, among others. The particles consist on metallic patterns etched on a dielectric and are inspired on the split ring resonator, SRR (that is, the formerly resonant particle used for the synthesis of left handed metamaterials). The different strategies for miniaturization are discussed and examples are given. It is shown that by using two metallic levels connected through vias it is possible to achieve very small electrical size for the particles (namely, below lambda/100, where lambda is the wavelength in the considered substrate at resonance). A method to determine the electrical parameters of the resonators in metamaterial transmission line configurations is also presented, and the possibility to determine the characteristics of the isolated particles is discussed. Finally, examples of application of this technique are presented. This work is of interest for the synthesis of effective media metamaterials based on resonant elements.

Optical cloaking with cylindrical plasmonic implants

In this contribution, we practically show the use of “antiphase” plasmonic scatterers to effectively reduce the scattering cross-section of a cylindrical dielectric object in the visible regime. By properly distributing a set of silver rods around a cylindrical inner core of silica, we demonstrate through a set of full-wave simulations the possibility to obtain a sensible reduction of the scattering phenomenon, achieving a condition of transparency for the structure.

A genetic algorithm based procedure to retrieve effective parameters of planar metamaterial samples

In this contribution, we present the employment of a Genetic Algorithm (GA) based procedure to retrieve the effective permittivity and permeability of planar metamaterial samples. The approach used here is the same of standard Transmission/Reflection (TR) techniques, consisting in extrapolating the sample properties by inversion of its scattering coefficients. The proposed procedure makes use of parametric models for describing the inherently dispersive behavior of the involved materials. This approach eliminates the anomalous behavior of most of the commonly used inversion techniques, providing a consistent representation of the material in the working frequency range. The transition to bulk effective parameters is also investigated determining a proper sample thickness assuring the validation of the homogenization procedure.