Optical device

An optical device comprising:

• a first waveguide extending in a first direction;
• and
• a second waveguide extending in the first direction including a first mirror having a first reflecting surface,
• a second mirror having a second reflecting surface facing the first reflecting surface,
• and an optical waveguide layer between the first mirror and the second mirror,
• wherein at least either the first waveguide or the second waveguide has one or more gratings in a part of an overlapping region in which the first mirror, the second mirror, and the first waveguide overlap one another when seen from an angle parallel with a direction perpendicular to the first reflecting surface, and the one or more gratings is at a distance that is longer than at least either a thickness of the first mirror or a thickness of the second mirror in the first direction from an end of the first mirror or the second mirror that is in the overlapping region.