Optical device, photodetection system, and method for manufacturing the same

An optical device comprising:

• a first substrate having a first surface spreading along a first direction and a second direction intersecting the first direction;
• a second substrate having a second surface that at least partially faces the first surface and that has a different area from an area of the first surface;
• at least one optical waveguide extending along the first direction between the first substrate and the second substrate;
• and
• a plurality of elastic spacers, disposed on at least either the first surface or the second surface, that include a first portion and a second portion, wherein:
• the first portion of the plurality of elastic spacers is at least one elastic spacer located in a region between the first substrate and the second substrate in which the first substrate and the second substrate overlap each other as seen from an angle parallel with a direction perpendicular to the first surface,
• the second portion of the plurality of elastic spacers is at least one elastic spacer located in a region in which the first substrate and the second substrate do not overlap each other as seen from an angle parallel with the direction perpendicular to the first surface,
• each of the at least one optical waveguide includes a first portion disposed in a region between the first substrate and the second substrate in which the first substrate and the second substrate overlap each other and a second portion disposed in a region in which the first substrate and the second substrate do not overlap each other,
• the at least one optical waveguide comprises a plurality of optical waveguides, and
• at least a part of the second portion of the plurality of elastic spacers is located around the second portion of each of the plurality of optical waveguides.