Lorena I. Basilio

Realizing optical magnetism from dielectric metamaterials.

We demonstrate, for the first time, an all-dielectric metamaterial resonator in the mid-wave infrared based on high-index tellurium cubic inclusions. Dielectric resonators are desirable compared to conventional metallo-dielectric metamaterials at optical frequencies as they are largely angular invariant, free of ohmic loss, and easily integrated into three-dimensional volumes. With these low-loss, isotropic elements, disruptive optical metamaterial designs, such as wide-angle lenses and cloaks, can be more easily realized.

The dependence of the input impedance on feed position of probe and microstrip line-fed patch antennas

The impedance of a rectangular patch antenna fed by an inset microstrip transmission line was measured for various feed positions. The dependence found was then compared to theoretical predictions both for this geometry and for the similar case of an inset coaxial probe feed.

A New Planar Dual-Band GPS Antenna Designed for Reduced Susceptibility to Low-Angle Multipath

A new Global Positioning System (GPS) microstrip patch antenna designed for dual-band (LI /L2) operation is introduced. The antenna design is based on the reduced-surface-wave (RSW) concept and, as a result, is much less susceptible to low-angle multipath interference effects than some of the more commonly-used high-precision GPS antennas. In this paper, the radiation characteristics of this new design was compared to a dual- band choke-ring and a dual-band pinwheel antenna. In addition to having the advantages typically associated with microstrip patch antennas, this planar dual-band antenna lacks the design complications associated with the frequently-used stacked-patch method for realizing dual-band microstrip antenna performance. Thus, the simplicity of the design, together with the reduced horizon and backside radiation levels and excellent circular polarization characteristics indicate that this new antenna design is a promising candidate for dual-band, high-precision applications.

A comparative study of a new GPS reduced-surface-wave antenna

A new global positioning system (GPS) antenna design based on the reduced-surface-wave (RSW) microstrip antenna concept is introduced. In addition to retaining the advantages common to microstrip antennas, these new GPS antennas will be shown to provide comparable performance to the most commonly used GPS antennas, including choke-ring designs. The reduced horizon and backside levels, and good circular polarization characteristics indicate that this new antenna design is ideal for high-precision GPS applications.

EIGER ™ : An open-source frequency-domain electromagnetics code

EIGERtrade is a general-purpose, 3D frequency-domain electromagnetics code suite consisting of a pre-processor (Jungfrau), the physics code (EIGER), and post processor (Moench). In order to better enable collaborative development, EIGERtrade version 2.0 has been approved for release as open source software under a GNU Public License. EIGERtrade is primarily an integral-equation code for both frequency-domain electromagnetics and electrostatics. This version includes the following Greens functions: 2D and 3D free space, symmetry-planes, periodic and layered media. There is a thin-wire algorithm as well as junction basis functions for attachment of a wire to a conducting surface, and also thin-slot models for coupling into cavities. The code is written in Fortran 90 using object-oriented design and has the capability to run both in parallel and serial.

Effect of thin silicon dioxide layers on resonant frequency in infrared metamaterials

Infrared metamaterials fabricated on semiconductor substrates exhibit a high degree of sensitivity to very thin (as small as 2 nm) layers of low permittivity materials between the metallic elements and the underlying substrate. We have measured the resonant frequencies of split ring resonators and square loops fabricated on Si wafers with silicon dioxide thicknesses ranging from 0 to 10 nm. Resonance features blue shift with increasing silicon dioxide thickness. These effects are explained by the silicon dioxide layer forming a series capacitance to the fringing field across the elements. Resonance coupling to the Si-O vibrational absorption has been observed. Native oxide layers which are normally ignored in numerical simulations of metamaterials must be accounted for to produce accurate predictions.

Perturbation Theory in the Design of Degenerate Rectangular Dielectric Resonators

The design of resonators with degenerate magnetic and electric modes usually requires the ability to perturb one or both types of modes in order to induce alignment of magnetic and electric properties. In this paper perturbation theory is used to identify difierent types of inclusions that can be used to realize fundamental- mode degeneracy in a rectangular dielectric resonator and thus, can ultimately be used in the design of negative-index metamaterials. For reasons associated with fabrication in the infrared-frequency regime, rectangular resonator designs are of particular interest.

A Quick and Easy Simulation Procedure to Aid in Metamaterial Unit-Cell Design

In this letter, a simple simulation procedure is presented and used to design a negative-index metamaterial unit cell. The procedure is based upon full-wave simulations of a single unit cell where electric and magnetic drives are separated to significantly simplify the interpretation of the effective-media response. More specifically, by extracting polarizabilities from the far-field response of the resonator under these drive conditions, the effective-media parameters are shown to be nicely correlated with the resonant responses of the resonator. For the purposes of demonstrating this simulation procedure, a negative-index metamaterial design based on a composite unit cell containing a split-ring-resonator and z-dipole is employed as a straightforward example.

Perturbation Theory in the Design of Degenerate Spherical Dielectric Resonators

The design of resonators with degenerate magnetic and electric modes for negative-index metamaterial applications usually requires the ability to perturb one or both types of modes in order to induce alignment of the negative magnetic and electric properties. The incentive behind the resonator designs presented in this paper is to minimize both the losses and the size of the unit cell, particularly in the case of high frequencies such as the infrared or visible. Thus, the designs discussed in this paper are based on degenerate-mode (the fundamental magnetic and electric modes are aligned in frequency) spherical dielectric resonators which rely on only a single-particle resonator and thereby do not require physical or electrical extensions of the unit cell, as might be seen with other negative-index unit cell designs. Cavity-perturbation techniques are used to arrive at the types of inclusions (in terms of material, polarization, and placement) that are necessary to realize a degenerate spherical dielectric resonator, as well as to derive simple formulas which can be used for the design of these types of resonators. Rigorous electromagnetic simulations of the degenerate resonators are also provided for comparison to the theoretical derivations.

Characteristics of an Inverted Shorted Annular-Ring-Reduced Surface-Wave Antenna

The electrical characteristics of an inverted shorted annular-ring-reduced surface-wave (RSW) antenna are presented in this letter. This microstrip antenna is designed for RSW excitation and lateral radiation and, hence, the characteristic patterns are relatively smooth in the forward region and demonstrate significantly reduced backscattered radiation, relative to a conventional microstrip patch. Results from a theoretical analysis of the antenna will be presented, along with confirming experimental results. These results include a radiation, input impedance, efficiency, bandwidth, directivity, and gain characterization of the antenna.