There is no variation and deterioration of the beam quality by the adhesive, and decrease of reliability be able to produce easily, the active side radiation device is developed even in the blood vessel and the like whose major diameter is thin small. One end of rod lens was welded on the end face of the optical fiber, other than that rod lens in the edge, portion of outer circle of cylinder the notch was done and the basic form which coming out plane of fire of parallel plane to axis was formed it is not, the point slantedly on the end face of thing or the optical fiber which welds the prism which possesses the advanced tilt slope which the notch is done the notch to do the portion of outer circle of cylinder, the basic form which formed the coming out plane of fire of parallel plane to axis it is not, the point slantedly by the fact that the prism lens which possesses the advanced tilt slope which the notch is done is welded the aforementioned topicIt solves.接着剤によるビーム品質のばらつきや劣化、信頼性の低下がなく、容易に製造でき、外径が小さく細い血管などにも使用可能な側方出射装置を開発する。光ファイバの端面にロッドレンズの一端を融着し、そのロッドレンズの他端に、円柱形の外周の一部を切欠し軸線に平行な平面状の出射面を形成した基本形状をなし、その先端部を斜めに切欠した先端傾斜面を有するプリズムを融着すること、又は光ファイバの端面に円柱形の外周の一部を切欠し軸線に平行な平面状の出射面を形成した基本形状をなし、その先端部を斜めに切欠した先端傾斜面を有するプリズムレンズを融着することで前記課題を解決する。
