Spatial mapping of the internal and external electromagnetic fields of negative index metamaterials

Bryan J Justice,David Schurig,David R Smith,Jack J Mock,Liheng Guo,Aloyse Degiron

doi:10.1364/oe.14.008694

Abstract

We perform an experimental study of the phase and amplitude of microwaves interacting with and scattered by two-dimensional negative index metamaterials. The measurements are performed in a parallel plate waveguide apparatus at X-band frequencies (8-12 GHz), thus constraining the electromagnetic fields to two dimensions. A detection antenna is fixed to one of the plates, while a second plate with a fixed source antenna or waveguide is translated relative to the first plate. The detection antenna is inserted into, but not protruding below, the stationary plate so that fields internal to the metamaterial samples can be mapped. From the measured mappings of the electric field, the interplay between the microstructure of the metamaterial lattice and the macroscopic averaged response is revealed. For example, the mapped phase fronts within a metamaterial having a negative refractive index are consistent with a macroscopic phase-in accordance with the effective medium predictions-which travels in a direction opposite to the direction of propagation. The field maps are in excellent agreement with finite element numerical simulations performed assuming homogeneous metamaterial structures.

Highlights

Metamaterials have brought about a new perspective to the field of electromagnetism [1, 2]
We extend the concept of point-by-point phase-sensitive field measurements to obtain spatial field maps of metamaterial samples within a two-dimensional planar waveguide apparatus
The electric field is sampled at intervals much finer than the dimension of the unit cell, providing unique information as to the interplay between the local microscopic properties and the averaged effective medium properties associated with actual fabricated metamaterials, which are in actuality far from homogenous

Summary

Introduction

Metamaterials have brought about a new perspective to the field of electromagnetism [1, 2]. We extend the concept of point-by-point phase-sensitive field measurements to obtain spatial field maps of metamaterial samples within a two-dimensional planar waveguide apparatus In these measurements, the electric field is sampled at intervals much finer than the dimension of the unit cell, providing unique information as to the interplay between the local microscopic properties and the averaged effective medium properties associated with actual fabricated metamaterials, which are in actuality far from homogenous. The electric field is sampled at intervals much finer than the dimension of the unit cell, providing unique information as to the interplay between the local microscopic properties and the averaged effective medium properties associated with actual fabricated metamaterials, which are in actuality far from homogenous These field maps can provide a decisive confirmation of the validity of the effective medium description of a metamaterial, in addition to being a useful general tool for assessing the performance of artificially structured materials. We are able to measure directly the negative phase advance within a negative index metamaterial wedge, correlating the internal backward waves with the external negative refracted waves

Experimental technique

Positive index wedge experiments

Negative index metamaterial wedge experiments

Conclusion