ABSTRACT
In 1852, W. Weber invoked Faraday’s law to suggest that natural diamagnetism could be produced by currents induced in microscopic conducting closed loops, which would be present inside matter. Spirals are well-known designs, widely used in planar microwave circuits as small-size inductors and resonators. However, spirals are low-symmetry structures and, in particular, they do not show inversion symmetry. Therefore, in spite of the fact that a quasi-static analysis does not predict them, bianisotropy and other cross-polarization effects can be present in metamaterials made from spiral resonators. Split ring resonators (SRRs) provide a simple and effective way for designing magnetic metamaterials with negative parameters. The behavior of SRRs at infrared and optical frequencies can be obtained from a straightforward extension of the aforementioned LC circuit model. The main effects at these frequencies are the saturation in the SRR frequency of resonance and a strong decrease in the SRR magnetic response.
