Active and passive meta-surfaces and their interaction with terahertz waves

Abul K. Azad
Center for Integrated Nanotechnologies, Material Physics Application Division
Los Alamos National Laboratory, New Mexico

Abstract:
Metamaterials have enabled many unprecedented electromagnetic phenomena including negative refraction, invisible cloaking, super lensing, and magnetism at optical frequencies, which are not accessible with naturally occurring materials. The fundamental building blocks of metamaterials are typically composed of sub-wavelength metallic resonators periodically patterned on dielectric substrates and these composites exhibit electromagnetic properties that are fundamentally different than those of composing materials. The bulk properties of metamaterials are mostly determined by resonant interactions of these mesoscopic elements with incident electromagnetic waves. A single layer planar metamaterial, called meta-surface, is often employed to yield specific electromagnetic properties using a co-design, bottom-up approach. The field of metamaterial may greatly improve the terahertz (THz) technology, where the lack of compact and efficient devices has created a technological vacuum, often called “THz-Gap”. Planar meta-surfaces are design, fabricated, and characterized to study their interactions with terahertz waves. The meta-surfaces are designed to optimize desired functionalities, for example, increase or decrease the resonance linewidths, enhance material absorption or reduce the Fresnel’s reflection losses, altering the polarization state, etc., by employing single or multi-elemental unit cells. In addition, a set of active meta-surfaces are demonstrated by the judicious incorporation of naturally occurring materials within the fundamental elements. Specifically, integration of semiconductor Schottky diodes or photoconductive patches within the meta-surface allows efficient and dynamic control of terahertz radiation by means of electrical or optical fields. Finally, we have a strong interest in developing compact terahertz technology for practical application and we are investigating meta-surfaces and their applicability towards the further growth of terahertz technology.

Bio:
Abul received his M. S. and Ph. D. degree in Electrical and Computer Engineering from Oklahoma State University in 2003 and 2006, respectively. His Ph.D. work focused on the demonstration of terahertz surface plasmons polaritons on metallic subwavelength hole arrays. From June 2006 to January 2007 he was working as a Postdoctoral Research Associate in the Department of Physics, Rensselaer Polytechnic Institute. Abul joined Los Alamos National Laboratory (LANL) in 2007. His current research interests include terahertz plasmonics, metamaterials, compact antenna, terahertz devices, and terahertz ultrafast spectroscopy for understanding the ultrafast dynamical properties of materials. He has published ~60 peer-reviewed journal articles in these areas.