Towards Negative Index Material:
Magnetic Response

 

Colin Scott
Senior Pratt Engineering Undergraduate Research Fellow
Electrical Engineering

 

Dr. Steven Cummer
Assistant Professor
Department of Electrical and Computer Engineering

 

Introduction

 

It has been proposed that a material that possesses a simultaneously negative permeability and permittivity would cause electromagnetic waves traveling through this medium to exhibit certain unnatural characteristics.  One of these properties is a reversal in the right-handed rule which the electric and magnetic fields follow with respect to the propagation vector of the wave.  In these materials there would be a left-handed relationship between these vector quantities, hence the name left-handed materials (LHM).  Another very interesting property is a negative refractive index for the material, hence the alternate name negative index material (NIM).  Materials that have such properties would be very useful in elecromagnetics.  They could be used in novel antennas, filters and waveguides for electromagnetic communications.  They could also improve semiconductor lithography techniques and near-field imaging techniques.

It has been proposed that materials with simultaneously negative permeability and permittivity can be realized by developing complex electromagnetic meta-materials.  Carefully designed lattices of conducting materials, which separately result in either negative permeability or permittivity, can be interlaced to obtain the concurrent properties.  It is the magnetic response of the negative permeability aspect of the overall meta-material upon which I have been conducting my research.

Results

 

I designed the building block of this artificial magnetic media, which was a split-ring resonator (SRR).  I simulated its properties using the electromagnetic software package Ansoft HFSS.  I confirmed its usefulness as the basic unit of the lattice by experimentally verifying its resonance resulting from magnetic induction.  I then designed and built a lattice of SRRs that would act as a homogenous, artificial magnetic medium that would have a negative permeability over a certain frequency range.  I experimentally verified that it performed as a material with the functional form of permeability as follows:

This is the functional form which would provide the appropriate magnetic response necessary for the production of NIM.