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A uniaxial chiral metamaterial is constructed by double-layered four "U" split ring resonators mutually twisted by 90 degrees. It shows a giant optical activity and circular dichroism. The retrieval results reveal that a negative refractive index is realized for circularly polarized waves due to the large chirality. The experimental results are in good agreement with the numerical results., Comment: 4 pages, 4 figures, Published as cover on APL

Cataloged from PDF version of article. We studied electrically small resonant antennas composed of split ring resonators (SRR) and monopoles. The antennas considered have the same ring radius, but slightly different geometry. The resonance frequency depends on the geometry of the SRRs. Two SRR antennas are designed. The first one, which operates at 3.62 GHz, is demonstrated theoretically and experimentally. The size of this antenna is 0.095 lambda(0)x0.100 lambda(0) and is low profile at the other dimension. The gain and directivity of the antenna was 2.38 and 5.46, respectively. The corresponding efficiency was 43.6%. The estimated radiation Q (rad Q=23.03) was much larger than the minimum radiation Q (min Q=1.78). The second one is a rather small SRR antenna in which the capacitance between the rings is increased. The size is reduced to 0.074 lambda(0)x0.079 lambda(0). This structure is called serrated SRR (SSRR). Both antennas have similar far-field patterns but the efficiency of the SSRR antenna is less. (c) 2007 American Institute of Physics.