How Does Our Metamaterial Work?

 

 

Metamaterials are engineered composites exhibiting properties that are not observed in the constituent materials and not observed in nature. Our metamaterial is composed of copper split ring resonators (SRRs) and wires on thin fiberglass circuit board material. We arranged the SRRs and wires into a two-dimensional structure with a 5mm lattice parameter. The figure (a) below is a diagram of an SRR. Figure (b) shows one unitcell. Notice that there are 6 SRRs and 2 wires per unitcell and that the wires are on the opposite side of the fiberglass as the SRRs.

 

The figure above is from: R. A. Shelby, D. R. Smith, S. Schultz, Appl. Phys. Lett. 78, 489 (2001).Copyright (2001) American Institute of Physics. This figure may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.

 

 

To start with, the index of refraction (n) is given by:

where ε is the permittivity, µ is the permeability, ε_o and µ_o are the free-space permittivity and permeability, respectively. Our material relies on the resonant response of the split ring resonators (SRRs) in the magnetic field of the microwave radiation to drive the permeability below zero on the high frequency side of the resonance and the resonant response of the wires in the electric fields. The general expressions for ε and µ are as follows:

 

 

Where ω_ep is the electric plasma frequency, ω_eo is the electric resonance frequency, ω_mp is the "magnetic plasma frequency", ω_mo is the magnetic resonance frequency. The following parameters were plugged into the previous equations to generate the plot below.

Notice that both µ and ε are negative from about 10.4 GHz to 11 GHz. This the frequency band where our material is left-handed.