Fused vertical directional couplers

Integrated waveguide couplers and switches are important devices for optical communication systems. In order to fabricate large size switches, it is essential to have compact, high extinction ratio directional couplers. In this paper we analyze the use of wafer fusion to give an extra degree of freedom in the fabrication of coupled waveguide structures. The technique of wafer fusion has been used to combine materials of very different lattice constant which could not be grown by heteroepitaxy