Microwave resonances of ultrathin hexagonally symmetric microcavity arrays

A metamaterial surface formed by three slot gratings at 60° to each other has two possible high-symmetry arrangements. One forms equilateral triangular metal patches, the other a combination of hexagons and small equilateral triangles. When spaced above a ground plane with a thin dielectric spacer both structures give strong microwave absorption at certain resonant frequencies, which is largely angle independent. The results of microwave reflectivity measurements are here presented for the two distinct sample geometries and compared with predictions from finite element method models.