Abstract: An electrically controlled optical device effective index includes a traveling wave electrode, a shield conductor and a thick buffer layer of a low dielectric constant. The thickness of an overlaid layer disposed between the traveling wave electrode and the shield conductor as well as the thickness of the buffer layer is so determined that an effective index of a microwave transmitted through the traveling wave electrode approaches an effective index of light transmitted through an optical waveguide, and that a microwave conductor loss is reduced, and that a characteristic impedance of said traveling wave electrode approaches a characteristic impedance of an associated external microwave circuit.

Abstract: An electrically controlled optical device includes a traveling wave electrode structure, a shield conductor and a thick buffer layer having a low dielectric constant. The thickness of an overlaid layer disposed between the traveling wave electrode structure and the shield conductor, as well as the thickness of the buffer layer, is determined so that the effective index of a microwave transmitted through the traveling wave electrode structure approaches the effective index of light transmitted through an optical waveguide, so that the microwave conductor loss is reduced, and so that the characteristic impedance of the traveling wave electrode structure approaches the characteristic impedance of an associated external microwave circuit.