A Multi-topic International Conference
UNCC_Honet logo_HONET    
11th HONET-PfE
Charlotte, North Carolina, USA
December 15 - 17, 2014 
     
Dr. Michael A. Fiddy
Professor of Physics & Optical Science, ECE,

UNC Charlotte, NC,USA                  
Email: mafiddy@uncc.edu

Title:Engineering the properties of metamaterials and some novel applications

Abstract:

Metamaterials research initially strived to realize extreme refractive index properties (e.g. very large, zero or negative values) by exploiting the combined effect of many subwavelength abstracted (high Q) resonant circuits. Extracting meaningful constitutive parameters like |ε|,|μ| or refractive index from distributions of sub-wavelength sized meta-atoms is not straightforward and the number of elements included obviously plays a role. These constitutive parameters are averaged quantities, implicitly relying on local volume averaging for their definition. Predicting these characteristics can be achieved using effective medium models, but these fail when excitation is near resonance. In practice, even the simplest components of metamaterials such as spheres (e.g. Mie-scatterers) or split-ring-like structures exhibit several resonances and these which hybridize as neighboring elements get closer. The coupling of fields between elements and the multiple scattering of local fields generally reduces the overall Q. This may usefully broaden operating bandwidth but can diminish desired large |ε| or |μ| values.   Moreover, meta-atom fabrication tolerances become more important when many such subwavelength elements are in close proximity, increasingly so for shorter operating wavelengths while keeping the meta-atom dimension, a << λ. Phase decoherence and averaging gives greater meaning to constitutive or homogenized response parameters but defects and disorder can diminish or destroy the kind of unique functionality structured materials offer. This explains the limited range of characteristics we find when using naturally occurring materials. This phenomenon is well known and embodied in the Random Phase Approximation (RPA). We indicate how one can make useful metamaterials for a variety of sensing, imaging and nonlinear applications by
i) designing more robust meta-atoms in the first place and
ii) determining how to exploit them in relatively small clusters so their coherent and scattering responses dominate over RPA. We illustrate these points and the significant discrepancies that can result if simpler effective medium models are incorrectly adopted in one's analysis or simulation of practical metamaterials.
  I would like to acknowledge the contributions to this presentation by Dr. Ray Tsu, Hossein Alisafaee, Max Burnett, Daniel Fullager, Morteza Karami, Steven Kitchin and Chris Rosenbury. Some of this work was supported by the NSF I/UCRC Center for Metamaterials.

Short Biography:

Michael Fiddy received his Ph.D. from the University of London, and was faculty member at Kings College from 1979-1987. He moved to the University of Massachusetts Lowell in 1987 where he was ECE Department Head from 1994 until 2001. In January 2002 he was appointed the founding director of the Center for Optoelectronics and Optical Communications at UNC Charlotte. He stepped down from this position in 2010 and has been site director for the NSF Industry/University Center for Metamaterials which began in 2011. He has been the editor-in-chief of the journal Waves in Random and Complex Media since 1996 and is Deputy Editor of OSA's recently launched Photonics Research Journal. He currently serves on the OSA Board of Directors and the Advisory Board of the Optoelectronics Industry Development Association (OIDA). He is a fellow of the OSA, IOP and SPIE.

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