Optical waveguide type directional coupler and optical waveguide circuit using the same

摘要

In one viewpoint, the invention is to provide an optical waveguide type directional coupler capable of reducing the wavelength dependency, the polarization dependency and variations in the coupling efficiency and to provide a small optical waveguide circuit using the same. An optical coupling part is provided in which a first optical waveguide and a second optical waveguide are arranged side by side to come close each other at the middle part in the longitudinal direction of the optical waveguides. At least one of the incident side of the first optical waveguide and the incident side of the second optical waveguide is adapted to be a light input part to the optical coupling part. At least one of the outgoing side of the first optical waveguide and the outgoing side of the second optical waveguide is adapted to be a light output part. The first and second optical waveguides in the optical coupling part are formed to be curved waveguide parts that project to the other optical waveguide side. A distance P' between peaks in a field distribution of a propagation light propagating from one side of the first and second optical waveguides to the other side thereof through the optical coupling part is made narrower than a distance P between core centers of the first and second optical waveguides in the optical coupling part.