Vibration device

A vibration device comprising:

• a cylindrical body including a cavity, a first opening end surface, and a second opening end surface;
• a light-transmissive cover directly or indirectly bonded to the first opening end surface of the cylindrical body so as to cover the cavity of the cylindrical body;
• a piezoelectric body directly or indirectly bonded to the cylindrical body;
• and
• a buffer layer between at least one of the cylindrical body and the piezoelectric body, and the cylindrical body and the light-transmissive cover;
• wherein
• when a direction connecting the first opening end surface and the second opening end surface of the cylindrical body is defined as an axial direction, the buffer layer includes an inner end portion on an inner side portion in a direction orthogonal or substantially orthogonal to the axial direction and an outer end portion on an outer side portion in a direction orthogonal to the axial direction;
• and
• a thickness of the inner end portion is larger than a thickness of the outer end portion.