title: Thin cylindrical diffusers in multimode Ge-doped silica fibers.
abstract: 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).
authors.affiliation: University Health Network, 610 University Avenue, Toronto, Ontario, Canada, M5G 2M9. llilge@uhnres.utoronto.ca
authors.forename: Lothar
authors.initials: L
authors.lastname: Lilge
authors.forename: Leonid
authors.initials: L
authors.lastname: Vesselov
authors.forename: William
authors.initials: W
authors.lastname: Whittington
mesh_terms: D004867:Equipment Design; D005336:Fiber Optic Technology; D005857:Germanium; D006801:Humans; D008422:Materials Testing; D055100:Optical Fibers; D010778:Photochemotherapy / Q000295:instrumentation*
chemical_list: D005857:Germanium