Thin cylindrical diffusers in multimode Ge-doped silica fibers.
OBJECTIVE
Cylindrical fiber diffusers are common tools in photodynamic therapy (PDT). However, large outer diameter and short length limit the indications to which they can be applied. Here a diffuser with an outer diameter of 250 microm and an active length exceeding 5 cm was developed.


METHODS
Diffusers based on photosensitive quartz optical fibers with a cladding diameter of 140 microm were developed using a structured beam from an excimer laser. A complete set of photometric characteristics, including longitudinal, polar, and azimuth radiance emission diagrams were collected.


CONCLUSIONS
The longitudinal radiance emission is homogenous to within +/-10%. The ability to create custom designed longitudinal emission profiles was demonstrated. The variations of the polar and azimuth radiance emission diagrams were within +/- 15% from an ideal Lambertian emitter. The polar uniformity can be improved with a slight increase of the outer diameter using a diffusing recoating compound. The residual light leakage at the distal end of the fiber diffuser was suppressed to 2%. The minimal bending radius after recoating is approximately 5 mm. Maximum power distribution is > 0.5 W cm(-1).
Lilge
Lothar
L
University Health Network, 610 University Avenue, Toronto, Ontario, Canada, M5G 2M9. llilge@uhnres.utoronto.ca
Vesselov
Leonid
L
Whittington
William
W
D004867:Equipment Design; D005336:Fiber Optic Technology; D005857:Germanium; D006801:Humans; D008422:Materials Testing; D055100:Optical Fibers; D010778:Photochemotherapy / Q000295:instrumentation*
D005857:Germanium