Refraction and band isotropy in 2D square-like Archimedean photonic crystal lattices.

In this paper we theoretically study refraction effects in the 2D square-like Archimedean photonic crystals (3(2), 4, 3, 4) and (4, 8(2)) made of dielectric rods in air. In addition, we investigated a band isotropy and band gap structure in these lattices. We compared the square and square-like structures as well, their refraction characteristics, zone structures and the level of band and band gap isotropy (bandwidth and band gap dependence on the wave vector). We found that square-like structures can have some advantages over the square ones regarding the completeness of the gap, its isotropy and the gap width. Also, due to the same square primitive unit cell and the first Brillouin zone, the square and square-like lattices have similar optical response in lower bands.