Insert and attachment member

An insert comprising:

• a hollow tube of which at least a portion is inserted into a subject;
• an optical fiber that is inserted into an inside portion of the hollow tube and guides light emitted from a light source;
• a base end section including an optical fiber insertion part used for inserting the optical fiber;
• a light absorbing member that absorbs light guided by the optical fiber in a case of being irradiated with the light and generates a photoacoustic wave;
• an optical fiber fixing member that fixes the optical fiber at a position spaced from a distal end of the optical fiber and is inserted into the optical fiber insertion part,
• wherein the optical fiber insertion part includes a first portion into which the optical fiber fixing member is inserted and which has at least three protrusions protruding toward the center at positions spaced from each other in a circumferential direction, and
• a size of the optical fiber fixing member in a direction perpendicular to an insertion direction into the first portion is larger than that of an inside portion of the first portion, and the optical fiber fixing member is fixed by the at least three protrusions of the first portion.