Left-handed materials composed of only S-shaped resonators

We analyze an $\mathsf{S}$-shaped inclusion for the realization of metamaterials exhibiting left-handed properties. Unlike most of the conventional inclusions used so far that are composed of two separate geometries—typically a split ring and a rod—the inclusion proposed in this paper is made of only one $\mathsf{S}$-shaped element which yields an overlapping negative permittivity and negative permeability response over a frequency band of about $2.6\mathrm{GHz}$. By adopting this geometry, we manage to lower the negative permittivity frequency band down to the level of the negative permeability frequency band, thus allowing the overlapping to occur. Therefore, the structure works as a stand alone and does not require the use of an additional rod. A theoretical analysis is carried out to study this inclusion and numerical simulations, as well as a Snell refraction experiment, clearly show that the material indeed exhibits a negative index of refraction at some frequencies. The simple pattern of the inclusion, the wide left-handed frequency band exhibited, and the low losses measured indicate the superiority of this inclusion in the realization of left-handed metamaterials.