Photonic crystal slabs with ring-shaped holes in a triangular lattice

We demonstrate a new type of photonic crystal made of a triangular lattice of ring-shape holes. We show that at low air-filling factors the photonic bandgap in such a photonic crystal is larger than in a conventional photonic crystal made of circular holes. To show the feasibility of such a photonic crystal, we manufactured a test structure in silicon-on-insulator