Patent ID: 6904220

Claim:
An optical waveguide for causing an optical signal to branch off or coupling optical signals, the waveguide comprising: a first substrate having a first optical waveguide core therein, the first optical waveguide core being parallel to a bottom face of the first substrate; and a second substrate having a second optical waveguide core therein, the second optical waveguide core being parallel to a top face of the second substrate, wherein an optical connecting portion is formed between the first and second optical waveguide cores by bonding the bottom face of the first substrate to the top face of the second substrate so as to overlap with each other, the first and second waveguide cores partially being in contact with each others, wherein the first optical waveguide core is formed by injecting a first high refractive index material having a relatively high refractive index into a first concave groove which is formed so as to be parallel to the bottom face of the first substrate, the second optical waveguide core is formed by injection a second high refractive index material having a relatively high refractive index into a second concave groove which is formed so as to be parallel to the top face of the second substrate, and the bottom face of the first substrate and the top face of the second substrate are bonded together by a third high refractive index material having a relatively high refractive index.