A structure includes: an optical fiber including a large-diameter section that is larger in diameter than a remainder of the optical fiber; and a glass block joined to a first end face of the large-diameter section of the optical fiber. The large-diameter section includes a tapering section that: includes, as part of a surface thereof, a sloping surface sloping at an angle of more than 0° and less than 90° to an optical axis of the optical fiber; and is disposed in a portion other than the first end face.