Patent ID: 8824044

Claim:
A planar optical waveguide element comprising: a core of an optical waveguide comprising: an inner side core having protruding portions that form a rib structure; and an outer side core that is provided on top of the inner side core, and covers upper and lateral surfaces of the protruding portions of the inner side core, wherein a refractive index of the outer side core is lower than an average refractive index of the inner side core; and a first Bragg grating pattern and a second Bragg grating pattern which are mutually parallel and extend along a propagation direction of guided light; wherein the first Bragg grating pattern comprises recessed and protruding portions that are formed on both outer side walls of the core along the propagation direction of guided light; wherein the second Bragg grating pattern comprises recessed and protruding portions that are formed, along the propagation direction of guided light, on both inner side walls of a groove that is formed on a top portion of the core at a center of the core in a width direction; and wherein the protruding portions of the first Bragg grating pattern where a core width is wide correspond with the protruding portions of the second Bragg grating pattern where a width of groove is narrow, and the recessed portions of the first Bragg grating pattern where the core width is narrow correspond with the recessed portions of the second Bragg grating pattern where the width of the groove is wide.