Attached to an optical fiber, this device delivers light approximately perpendicular to the fiber axis. Matching of the irradiated area to the target area is accomplished by choosing distributors covering sectors with a central angle of 90 degree(s), 180 degree(s), or 360 degree(s), respectively, and by axial scanning. Since the deviation of light is obtained by total reflection the transmission efficiency is high, about 91 at 630 nm. This allows one to apply high intensities (test power 7 W cw from a YAG laser). Light of shorter wavelengths can be used if a slight decrease of the transmission efficiency is acceptable. Further advantages are the small diameter of 2.6 mm (there is also a miniature version having 1.6 mm diam) and the mechanical strength. The clinical effectiveness of the device has been demonstrated for PDT. It might be useful for laser hyperthermia as well.
P. Lenz, P. Lenz,
"Light distributor for endoscopic photochemotherapy", Proc. SPIE 1525, Future Trends in Biomedical Applications of Lasers, (1 November 1991); doi: 10.1117/12.48216; https://doi.org/10.1117/12.48216