arXiv subjects

D. Schurig

Publications and source records attributed to D. Schurig.

11 recordsLinked to original sources

arXiv2025

Controlling Electromagnetic Fields

Using the freedom of design which metamaterials provide, we show how electromagnetic fields can be redirected at will and propose a design strategy. The conserved fields: electric displacement field, D, magnetic induction field, B, and Poynting vector, S, are all displaced in a consistent manner. A simple illustration is given of the cloaking of a proscribed volume of space to exclude completely all electromagnetic fields. Our work has relevance to exotic lens design and to the cloaking of objects from electromagnetic fields

physics.optics↗

arXiv2025

Demonstration of a Metamaterial Electromagnetic Cloak at Microwave Frequencies

Combining the tools for transforming space-time developed for General Relativity with the capabilities of artificially structured metamaterials, an entirely new means of controlling electromagnetic fields has emerged. Here, we utilize a coordinate transformation in which a hole is opened up in space. The transformation provides a complete prescription for an electromagnetic cloak which, although complex, can be readily constructed with metamaterials

physics.optics↗

arXiv2016

First Upper Limits on the Radar Cross Section of Cosmic-Ray Induced Extensive Air Showers

TARA (Telescope Array Radar) is a cosmic ray radar detection experiment colocated with Telescope Array, the conventional surface scintillation detector (SD) and fluorescence telescope detector (FD) near Delta, Utah, U.S.A. The TARA detector combines a 40 kW, 54.1 MHz VHF transmitter and high-gain transmitting antenna which broadcasts the radar carrier over the SD array and within the FD field of view, towards a 250 MS/s DAQ receiver. TARA has been collecting data since 2013 with the primary goal of observing the radar signatures of extensive air showers (EAS). Simulations indicate that echoes are expected to be short in duration (~10 microseconds) and exhibit rapidly changing frequency, with rates on the order of 1 MHz/microsecond. The EAS radar cross-section (RCS) is currently unknown although it is the subject of over 70 years of speculation. A novel signal search technique is described in which the expected radar echo of a particular air shower is used as a matched filter template and compared to waveforms obtained by triggering the radar DAQ using the Telescope Array fluorescence detector. No evidence for the scattering of radio frequency radiation by EAS is obtained to date. We report the first quantitative RCS upper limits using EAS that triggered the Telescope Array Fluorescence Detector.

astro-ph.IM↗

arXiv2015

Design, Construction and Operation of a Low-Power, Autonomous Radio-Frequency Data-Acquisition Station for the TARA Experiment

Employing a 40-kW radio-frequency transmitter just west of Delta, UT, and operating at 54.1 MHz, the TARA (Telescope Array RAdar) experiment seeks radar detection of extensive air showers (EAS) initiated by ultra-high energy cosmic rays (UHECR). For UHECR with energies in excess of $10^{19}$ eV, the Doppler-shifted "chirps" resulting from EAS shower core radar reflections should be observable above background (dominantly galactic) at distances of tens of km from the TARA transmitter. In order to stereoscopically reconstruct cosmic ray chirps, two remote, autonomous self-powered receiver stations have been deployed. Each remote station (RS) combines both low power consumption as well as low cost. Triggering logic, the powering and communication systems, and some specific details of hardware components are discussed.

astro-ph.IM↗

arXiv2006

Calculation of material properties and ray tracing in transformation media

Complex and interesting electromagnetic behavior can be found in spaces with non-flat topology. When considering the properties of an electromagnetic medium under an arbitrary coordinate transformation an alternative interpretation presents itself. The transformed material property tensors may be interpreted as a different set of material properties in a flat, Cartesian space. We describe the calculation of these material properties for coordinate transformations that describe spaces with spherical or cylindrical holes in them. The resulting material properties can then implement invisibility cloaks in flat space. We also describe a method for performing geometric ray tracing in these materials which are both inhomogeneous and anisotropic in their electric permittivity and magnetic permeability.

physics.optics↗

arXiv2004

A gradient index metamaterial

Metamaterials--artificially structured materials with tailored electromagnetic response--can be designed to have properties difficult to achieve with existing materials. Here we present a structured metamaterial, based on conducting split ring resonators (SRRs), which has an effective index-of-refraction with a constant spatial gradient. We experimentally confirm the gradient by measuring the deflection of a microwave beam by a planar slab of the composite metamaterial over a broad range of frequencies. The gradient index metamaterial represents an alternative approach to the development of gradient index lenses and similar optics that may be advantageous, especially at higher frequencies. In particular, the gradient index material we propose may be suited for terahertz applications, where the magnetic resonant response of SRRs has recently been demonstrated.

physics.optics↗

arXiv2004

Negative Index Lens Aberrations

We examine the Seidel aberrations of thin spherical lenses composed of media with refractive index not restricted to be positive. We find that consideration of this expanded parameter space allows reduction or elimination of more aberrations than is possible with only positive index media. In particular we find that spherical lenses possessing real aplanatic focal points are possible only with negative index. We perform ray tracing, using custom code that relies only on Maxwell's equations and conservation of energy, that confirms the results of the aberration calculations.

physics.optics↗

arXiv2003

Universal Description of Spherical Aberration Free Lenses Composed of Positive or Negative Index Media

We find that the function that describes the surface of spherical aberration free lenses can be used for both positive and negative refractive index media. With the inclusion of negative index, this function assumes the form of all the conic sections and expands the theory of aplanatic optical surfaces. There are two different symmetry centers with respect to the index that create an asymmetric relationship between positive and negative index lens profiles. In the thin lens limit the familiar formulas for image position and magnification hold for any index.

physics.optics↗

arXiv2002

Electromagnetic Wave Propagation in Media with Indefinite Permittivity and Permeability Tensors

We study the behavior of wave propagation in materials for which not all of the principle elements of the permeability and permittivity tensors have the same sign. We find that a wide variety of effects can be realized in such media, including negative refraction, near-field focusing and high impedance surface reflection. In particular a bi-layer of these materials can transfer a field distribution from one side to the other, including near-fields, without requiring internal exponentially growing waves.

cond-mat.mtrl-sci↗

arXiv2002

Limitations on Sub-Diffraction Imaging with a Negative Refractive Index Slab

Recently it has been proposed that a planar slab of material, for which both the permittivity and permeability have the values of -1, could bring not only the propagating fields associated with a source to a focus, but could also refocus the nonpropagating near-fields, thereby achieving a subdiffraction image. In this work we discuss the sensitivity of the subwavelength focus to various slab parameters, pointing out the connection to slab plasmon modes. We also note and resolve a paradox associated with the perfect imaging of a point source. We conclude that subwavelength resolution is achievable with available technology, but only by implementation of a critical set of design parameters.

cond-mat↗

arXiv2002

The asymmetric lossy near-perfect lens

We extend the ideas of the recently proposed perfect lens [J.B. Pendry, Phys. Rev. Lett. {\bf 85}, 3966 (2000)] to an alternative structure. We show that a slab of a medium with negative refractive index bounded by media of different positive refractive index also amplifies evanescent waves and can act as a near-perfect lens. We examine the role of the surface states in the amplification of the evanescent waves. The image resolution obtained by this asymmetric lens is more robust against the effects of absorption in the lens. In particular, we study the case of a slab of silver, which has negative dielectric constant, with air on one side and other media such as glass or GaAs on the other side as an `asymmetric' lossy near-perfect lens for P-polarized waves. It is found that retardation has an adverse effect on the imaging due to the positive magnetic permeability of silver, but we conclude that subwavelength image resolution is possible inspite of it.

cond-mat↗