Diffusing fibre tips for high-power medical laser applications

For most applications in laser medicine suitable delivery systems are required. We developed fibre optic based diffusing tips especially for Photodynamic Therapy (PDT) and Laser Induced Thermotherapy (LifT). To realize an adequate emitting cylindrical diffuser the fibre core was abraded by a precision cutter. Hence, the use of scattering media such as TiO₂-doped polymers is avoided. Because the diffuser size is mainly determined by the manipulated fibre and a surrounding glass cappillary, one can realize small diameters (Ø ≈ 3mm). The laser light is distributed mainly by surface scattering and total reflection at the fibre air boundary. Because the use of absorbing media is avoided, it is possible to apply high laser power as necessary in LiTT and pulsed PDT. We produced diffusing tips with lengths of several centimeters and typical diameters of 3 mm. By controlling the fibre-shaping process, a homogenous intensity profile or even special designs can be achieved. The control is done by either on-line camera surveillance or calculated predictions. A delivery system especially for the photodynamical treatment of female cervix displasia has been designed.