title: Comparison of germanium oxide fibers with silica and sapphire fiber tips for transmission of erbium: YAG laser radiation.
abstract: OBJECTIVE
  Endoscopic applications of the Erbium:YAG laser have been limited due to the lack of a suitable optical fiber delivery system. The purpose of this study was to compare the transmission of Er:YAG laser radiation through germanium oxide trunk fibers with silica and sapphire fiber tips for potential use in contact tissue ablation during endoscopy.
  
  
  METHODS
  Er:YAG laser radiation with a wavelength of 2.94 microm, pulse length of 300 microseconds, pulse energies from 5 to 1,360 mJ, coupled into pulse repetition rates of 3-10 Hz, was through 1-m-long germanium oxide fibers with either 1-cm-long, 550-microm-diameter silica or sapphire tips.
  
  
  RESULTS
  Transmission through the germanium oxide/sapphire fibers measured 65+/-5% compared with 55+/-4% for the germanium oxide/silica fibers (P<0.05). The damage threshold for the hybrid fibers averaged 309+/- 44 mJ and 126+/-43 mJ, respectively (n = 7 fibers each) (P<0.05). The highest pulse energies transmitted through the fibers were 700 mJ and 220 mJ, respectively.
  
  
  CONCLUSIONS
  Improved index-matching of the trunk fiber and fiber tip at 2.94 microm resulted in higher transmission and damage thresholds for the germanium oxide/sapphire fibers. The germanium oxide/sapphire fiber may represent a promising mid-infrared optical fiber delivery system for use in endoscopic applications of the Er:YAG laser requiring a flexible, biocompatible, and robust fiber delivery system for contact tissue ablation.
authors.affiliation: Department of Urology, Johns Hopkins University, Baltimore, Maryland 21224, USA.
authors.forename: Travis J
authors.initials: TJ
authors.lastname: Polletto
authors.forename: Anthony K
authors.initials: AK
authors.lastname: Ngo
authors.forename: Alexei
authors.initials: A
authors.lastname: Tchapyjnikov
authors.forename: Ken
authors.initials: K
authors.lastname: Levin
authors.forename: Danh
authors.initials: D
authors.lastname: Tran
authors.forename: Nathaniel M
authors.initials: NM
authors.lastname: Fried
mesh_terms: D000537:Aluminum Oxide; D019723:Endoscopes; D004867:Equipment Design; D004871:Erbium; D005336:Fiber Optic Technology; D005857:Germanium; D053685:Laser Therapy / Q000295:instrumentation*; D055100:Optical Fibers; D012822:Silicon Dioxide
chemical_list: D005857:Germanium; C040516:germanium oxide; D012822:Silicon Dioxide; D004871:Erbium; D000537:Aluminum Oxide