Single-mode waveguide structure for optoelectronic integrated circuits

Abstract

An optical waveguide for use in an optoelectronic integrated circuit and the associated method of manufacturing such a waveguide. The waveguide is formed by the successive layering of varied waveguide materials on a III-V semiconductor substrate, thereby producing a slab waveguide. The various layers within the slab waveguide are relatively thick, thereby producing a slab waveguide that is sized to be more compatible with an optical fiber and therefore more readily coupled to an optical fiber. The larger slab waveguide structure broadens the fundamental mode of the optical signal. However, multiple modes are also produced in the thicker slab waveguide that include higher order modes. A ridge structure is etched into the slab waveguide, wherein the width and height of the ridge structure are selected to impose lateral confinements on the higher order slab modes. The result is a waveguide that has a broadened fundamental mode yet is essentially single-mode. The resulting broadened fundamental mode is closer in symmetry to the mode of standard optical fibers, thereby enabling the waveguide to be more efficiently coupled to an optical fiber.