Optical circuit element and configuration method for the optical circuit element

An optical circuit element constructed of a rib type optical waveguide constructed of a core region that includes a flat platy slab and a protruding rib and cladding regions that are provided in contact with a top and a bottom of the core region, wherein

• a first optical waveguide included in the optical circuit element includes a plurality of intersection points at which the first optical waveguide intersects optical waveguides other than the first optical waveguide,
• the plurality of intersection points are disposed on one straight line,
• a region in the first optical waveguide that is formed between the plurality of intersection points is constructed as a first region in which an optical signal, including a fundamental mode and a higher mode, propagates,
• the first region and a second region in which the optical signal, including only the fundamental mode, propagates in the first optical waveguide, are interconnected by a taper optical waveguide, and
• a thickness of the slab of the first region is larger than a thickness of the slab of the second region reducing loss and polarization dependency in the higher mode.

A configuration method for an optical circuit element constructed of a core region that includes a flat platy slab and a protruding rib and cladding regions that are provided in contact with a top and a bottom of the core region, wherein

• a plurality of intersection points at which a first optical waveguide included in the optical circuit element intersects optical waveguides other than the first optical waveguide are disposed on the first optical waveguide,
• the plurality of intersection points are disposed on one straight line,
• a core width of the first optical waveguide in a region between the plurality of intersection points is set wider than a core width of the first optical waveguide in regions other than the region between the intersection points,
• regions of the first optical waveguide that are different in the core width from each other are interconnected by a taper optical waveguide whose core width monotonously changes, and
• a thickness of the slab of the first optical waveguide in a region whose core width is wide is set larger than a thickness of the slab of the first optical waveguide in regions other than the region whose core width is wide.