Wider bandwidth with high transmission through waveguide bends in two-dimensional photonic crystal slabs

We demonstrate the use of a defect to improve the transmission property of waveguide bends in two-dimensional photonic crystal slabs. We show that high reflection in the two-dimensional photonic crystal slab previously reported is due to the fact that the waveguide is multimoded at the bend while it is single moded along the straight waveguide. By making the waveguide single moded at the bend, the transmission property can be significantly improved. An extension of more than twice of high-transmission bandwidth is achieved.