Richard Ziolkowski

Abstract:  There continues to be a great desire for high performance electrically small radiating and scattering systems from the microwave to the optical regimes whose physical characteristics and electromagnetic responses could be tailored to satisfy a wide range of applications.  Metamaterials, artificial materials whose electromagnetic responses can in principle be engineered to any negative or positive value, have been shown recently to be a potential enabling technology for these radiating and scattering systems.

Traditional electrically small radiating and scattering systems are poor transducers of their input or excitation energy.  Several metamaterial-based configurations have been demonstrated recently that significantly improve the radiating and scattering performance characteristics of these systems.  The resulting systems are resonant despite being significantly sub-wavelength in size.  For instance, an electrically-small epsilon-negative (ENG) or double negative (DNG) spherical shell surrounding an electrically-small dipole antenna can be designed to act as an effective distributed inductor that is properly matched to the capacitive electric dipole element to form a naturally resonant LC structure, as well as to act as a resistive matching element to the source.  Thus, an overall efficiency of 100% can be achieved theoretically in such an electrically-small radiating system.  The reciprocal configuration, plane wave scattering from an electrically-small ENG or DNG metamaterial-coated sphere, has been shown to exhibit unity scattering.  Moreover, by introducing gain media, the effects of losses and dispersion can be controlled.  For instance, lasing has been demonstrated at visible wavelengths in an electrically-small metal coated nano-particle.

A review of the progress to date on all of these resonant metamaterial-based electrically small radiating and scattering systems, and their potential practical microwave and optical realizations will be given.  Practical issues, including losses and dispersion, will be emphasized in the discussion.