Flat photonic bands in two-dimensional photonic crystals with kagome lattices

We theoretically demonstrate flat photonic bands in two-dimensional photonic crystals with kagome lattices. In such photonic crystals composed of circular rods, electromagnetic waves localizing at the rods form flat photonic bands. The flat photonic bands are important for the omnidirectional lasing and the enhancement of the omnidirectional electromagnetic interaction of materials. Dependences of flat photonic bands on the dielectric constant and radii of rods are discussed.