High transmission through waveguide bends by use of polycrystalline photonic-crystal structures

A hybrid photonic-crystal structure is presented as a candidate for enhancing transmission through sharp photonic-crystal waveguide bends built on a perforated dielectric slab. This structure, which we refer to as a polycrystalline structure, combines two photonic-crystal lattices. Polycrystalline photonic-crystal structures offer the ability to minimize reflections as well as mismatches that a propagating wave might encounter while undergoing a sharp corner or a discontinuity between different waveguide sections. The availability of polycrystalline structures in photonic crystals opens a broad range of possibilities for the development of optical devices. Numerical experiments are performed with two- and three-dimensional finite-difference time domain methods.