Using the freedom of design that 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 B-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.

/pdf/controlling-electromagnetic-fields-3ryxkryf1t.pdf

Controlling Electromagnetic Fields

A recently published theory has suggested that a cloak of invisibility is in principle possible, at least over a narrow frequency band. We describe here the first practical realization of such a cloak; in our demonstration, a copper cylinder was "hidden" inside a cloak constructed according to the previous theoretical prescription. The cloak was constructed with the use of artificially structured metamaterials, designed for operation over a band of microwave frequencies. The cloak decreased scattering from the hidden object while at the same time reducing its shadow, so that the cloak and object combined began to resemble empty space.

/pdf/metamaterial-electromagnetic-cloak-at-microwave-frequencies-1qj4zdgl8e.pdf

Metamaterial Electromagnetic Cloak at Microwave Frequencies

Conventional optical components rely on gradual phase shifts accumulated during light propagation to shape light beams. New degrees of freedom are attained by introducing abrupt phase changes over the scale of the wavelength. A two-dimensional array of optical resonators with spatially varying phase response and subwavelength separation can imprint such phase discontinuities on propagating light as it traverses the interface between two media. Anomalous reflection and refraction phenomena are observed in this regime in optically thin arrays of metallic antennas on silicon with a linear phase variation along the interface, which are in excellent agreement with generalized laws derived from Fermat’s principle. Phase discontinuities provide great flexibility in the design of light beams, as illustrated by the generation of optical vortices through use of planar designer metallic interfaces.

http://www.zenogaburro.it/papers/LightPropagation.pdf

Light Propagation with Phase Discontinuities: Generalized Laws of Reflection and Refraction

We present the design for an absorbing metamaterial (MM) with near unity absorbance A(omega). Our structure consists of two MM resonators that couple separately to electric and magnetic fields so as to absorb all incident radiation within a single unit cell layer. We fabricate, characterize, and analyze a MM absorber with a slightly lower predicted A(omega) of 96%. Unlike conventional absorbers, our MM consists solely of metallic elements. The substrate can therefore be optimized for other parameters of interest. We experimentally demonstrate a peak A(omega) greater than 88% at 11.5 GHz.

Perfect metamaterial absorber.

Metamaterials are artificially fabricated materials that allow for the control of light and acoustic waves in a manner that is not possible in nature. This Review covers the recent developments in the study of so-called metasurfaces, which offer the possibility of controlling light with ultrathin, planar optical components. Conventional optical components such as lenses, waveplates and holograms rely on light propagation over distances much larger than the wavelength to shape wavefronts. In this way substantial changes of the amplitude, phase or polarization of light waves are gradually accumulated along the optical path. This Review focuses on recent developments on flat, ultrathin optical components dubbed 'metasurfaces' that produce abrupt changes over the scale of the free-space wavelength in the phase, amplitude and/or polarization of a light beam. Metasurfaces are generally created by assembling arrays of miniature, anisotropic light scatterers (that is, resonators such as optical antennas). The spacing between antennas and their dimensions are much smaller than the wavelength. As a result the metasurfaces, on account of Huygens principle, are able to mould optical wavefronts into arbitrary shapes with subwavelength resolution by introducing spatial variations in the optical response of the light scatterers. Such gradient metasurfaces go beyond the well-established technology of frequency selective surfaces made of periodic structures and are extending to new spectral regions the functionalities of conventional microwave and millimetre-wave transmit-arrays and reflect-arrays. Metasurfaces can also be created by using ultrathin films of materials with large optical losses. By using the controllable abrupt phase shifts associated with reflection or transmission of light waves at the interface between lossy materials, such metasurfaces operate like optically thin cavities that strongly modify the light spectrum. Technology opportunities in various spectral regions and their potential advantages in replacing existing optical components are discussed.

Flat Optics With Designer Metasurfaces

Experimental characterization of magnetic surface plasmons on

This paper reports on efforts to create fully left-handed meta-materials at multi-THz frequencies, detailed optical characterizations of various structures fabricated, and understanding to date of what the materials limitations are for making these structures smaller and smaller Presently, authors are using CXRO's nano-writer to create sub-micron structures with 60 nm smallest features Present results on these and other nano-fabricated structures with resonance frequencies in the 100 THz and higher range

/pdf/fabrication-and-optical-measurements-of-nanoscale-meta-1hm04zcedc.pdf

Fabrication and optical measurements of nanoscale meta-materials: terahertz and beyond

Apparatus, methods, and systems provide conversion of evanescent electromagnetic waves to non-evanescent electromagnetic waves and/or conversion of non-evanescent electromagnetic waves to evanescent electromagnetic waves. In some approaches the conversion includes propagation of electromagnetic waves within an indefinite electromagnetic medium, and the indefinite medium may include an artificially-structured material such as a layered structure or other metamaterial.

Evanescent electromagnetic wave conversion apparatus and methods

The prelims comprise: Introduction Geometric Optics Gaussian Optics Aberrations References

Negative Index Lenses

An effective method for preparing thin films of colossal magnetoresistance (CMR) materials is by pulsed laser deposition (PLD). We have studied such films by measuring the temperature and field dependence of dc resistance, magnetization, and specifically ferromagnetic resonance (FMR). With PLD it is possible to prepare samples with reasonable homogeneity as observed with x-ray diffraction and Rutherford backscattering. However, we have found that samples that appear to be reasonably, crystalographically homogeneous are not necessarily magnetically homogeneous. We believe that a powerful technique for examining magnetic homogeneity in this class of CMR samples is via FMR. In FMR, the resonance linewidth is an indicator of the average sample homogeneity, but this technique is much more informative when used in a scanning mode that we have developed. Scanning FMR data will be shown for several CMR samples prepared from La0.7R0.3MnO3 (R=Ca, Ba) targets using PLD. We find that some complex multiline spectra (o...

David Schurig

Papers

Experimental characterization of magnetic surface plasmons on

Fabrication and optical measurements of nanoscale meta-materials: terahertz and beyond

Evanescent electromagnetic wave conversion apparatus and methods

Negative Index Lenses

Spatial homogeneity of thin films of colossal magnetoresistance materials by scanning ferromagnetic resonance (abstract)