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Abstracts and Talk Materials
Negative Index Materials
October 2-4, 2006


Allan Boardman (University of Salford)
http://www.imr.salford.ac.uk/people/academic staff/allan boardman.shtml

Radiation enhancement and radiation suppression by a left-handed metamaterial
December 31, 1969

Joint work with K. Marinov (Photonics and Nonlinear Science Group, Joule Laboratory, Department of Physics, University of Salford, Salford M5 4WT, UK).

It is shown that the perfect lens property of the left-handed metamaterials can be exploited to control the radiation efficiency of an electromagnetic radiation source (e.g. an antenna). In particular, the radiation characteristics of two identical sources, in the focal planes of the lens can be controlled depending on the relative phase difference between their feeding voltages. When the feeding voltages are pi-out-of-phase the resulting system behaves as a non-radiating configuration with a strong electromagnetic field confined in the space between the lens and the emitters and almost no electromagnetic radiation emitted. It is shown that such a system can be used as a very sensitive detector since any object disturbing the configuration of the electromagnetic fields inside the system stimulates radiation. Even objects of subwavelength dimensions are able to produce a substantial increase of the total power emitted by the system, and thus their presence can be revealed. The finite-difference time-domain (FDTD) numerical analysis performed allows a realistic system performance evaluation to be made. It is shown that if a pair of identical sources driven with in-phase feeding voltages are used in the same resonant configuration this results in an increase of the radiation resistance of each of the sources. The latter property can be useful for small antennas.

Nader Engheta (University of Pennsylvania)
http://www.ese.upenn.edu/~engheta/

Metamaterials, plasmonics and optical nanocircuits
October 4, 2006

Metamaterials, which are engineered composite media with unconventional electromagnetic and optical properties, can be formed by embedding sub-wavelength inclusions as artificial molecules in host media in order to exhibit specific desired response functions. They can have exciting characteristics in manipulating and processing RF, microwave, IR and optical signal information. Various features of these media are being investigated and some of the fundamental concepts and theories and modeling of wave interaction with a variety of structures and systems involving these material media are being developed. From our analyses and simulations, we have found that the devices and components formed by these media may be ultracompact and subwavelength, while supporting resonant and propagating modes. This implies that in such structures RF, microwave, IR and optical signals can be controlled and reshaped beyond the diffraction limits, leading to the possibility of miniaturization of optical interconnects and design and control of near-field devices and processors for the next generation of information technology. This may also lead to nano-architectures capable of signal processing in the near-field optics, which has the potential for significant size reduction in information processing and storage. Furthermore, the nanostructures made by pairing these media can be compact resonant components, resulting in either enhanced wave signatures and higher directivity or in transparency and scattering reduction. We are also interested in nano-optics of metamaterial structures that effectively act as lumped nano-circuit-elements. These may provide nano-inductors, nano-capacitors, nano-resistors, and nanodiodes as part of field nanocircuits in the optical regimes or optical-field nanoelectronics--, and can provide roadmaps to more complex nanocircuits and systems formed by collection of such nanostructures. All these characteristics may offer various potential applications in high-resolution near-field imaging and microscopy, enhancement or reduction of wave interaction with nano-particles and nano-apertures, nanoantennas and arrays, far-field sub-diffraction optical microscopy (FSOM), nano-circuit-filters, optical data storage, nano-beam patterning and spectroscopy, optical-molecular signaling and optical coupling and interfacing with cells, to name a few. In this talk, we present an overview of the concepts, salient features, recent developments, and some of the potential applications of these metamaterials and structures, and will forecast some futures ideas and directions in this area.

Alexander Figotin (University of California)

Abnormal refraction of EM waves in periodic metamaterials
October 4, 2006

Joint work with I Vitebskiy.

Wave propagation in spatially periodic media, such as photonic crystals, can be qualitatively different from any uniform substance. The differences are particularly pronounced when the electromagnetic wavelength is comparable to the minimal translation of the periodic structure. In such a case, the periodic medium cannot be assigned any meaningful refractive index. Still, such important features as negative refraction and/or opposite phase and group velocities for certain directions of light propagation can be found in almost any photonic crystal. The only reservation is that unlike hypothetical uniform left-handed media, photonic crystals are essentially anisotropic at frequency range of interest. Consider now a plane wave incident on a semi-infinite photonic crystal. One can assume, for instance, that in the case of positive refraction, the normal components of the group and the phase velocities of the transmitted Bloch wave have the same sign, while in the case of negative refraction, those components have opposite signs. What happens if the normal component of the transmitted wave group velocity vanishes? Let us call it a "zero-refraction" case. At first sight, zero normal component of the transmitted wave group velocity implies total reflection of the incident wave. But we demonstrate that total reflection is not the only possibility. Instead, the transmitted wave can appear in the form of an abnormal grazing mode with huge amplitude and nearly tangential group velocity. This spectacular phenomenon is extremely sensitive to the frequency and direction of propagation of the incident plane wave. We also discuss some possible applications of this effect.

REFERENCES:

- A. Figotin, and I. Vitebskiy. Phys. Rev. E68, 036609 (2003).

- J. Ballato, A. Ballato, A. Figotin, and I. Vitebskiy. Phys. Rev. E71, (2005).

Rachel S. Goldman (University of Michigan)
http://www.mse.engin.umich.edu/people/faculty/goldman

Directed seeding of three-dimensional metal-semiconductor nanocomposites for negative index metamaterials
December 31, 1969

Negative index of refraction materials (NIMs) are promising for several applications including near-field imaging and steering of EM radiation. Although NIMs have been demonstrated using hybrid metamaterials at microwave frequencies, high losses and narrow bandwidths are presently limiting their wide application. We are developing a novel approach to fabricating low-loss high density NIM semiconductor-metal nanocomposites, which consists of alternating sequences of focused-ion beam nanopatterning of metallic droplet arrays and film growth using molecular-beam epitaxy. We will discuss the formation and ordering of Ga and In droplets and droplet motifs on a variety of semiconductor surfaces. In addition, we will discuss the extension of this approach to 3D. In particular, information from scattering measurements of 1D and 2D droplet motifs will be input into theoretical NIMs calculations to guide the fabrication of 3D arrays of appropriate motifs.

Anand Gopinath (University of Minnesota, Twin Cities)
http://www.msi.umn.edu/cgi-bin/pi/pi_detail.html?piid=1040
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