OPTICAL WAVEGUIDE, LASER INCLUDING OPTICAL WAVEGUIDE, MODULE INCLUDING OPTICAL WAVEGUIDE, AND METHOD OF MANUFACTURING OPTICAL WAVEGUIDE

摘要

PROBLEM TO BE SOLVED: To solve the problem that the increase in depth of a diffraction grating causes light scattering to bring about a loss though being able to increase a coupling coefficient (&kgr;) of the diffraction grating.SOLUTION: An optical waveguide includes a plurality of first optical waveguides provided with diffraction gratings and a plurality of second optical waveguides provided with no diffraction gratings, and the first optical waveguides and the second optical waveguides are alternately and repeatedly optically coupled in a propagation direction, and an effective refractive index of the first optical waveguide is lower than that of the second optical waveguide.