INFLUENCE OF HYDROGEN ON THE COLOR-CENTER FORMATION IN OPTICAL FIBERSINDUCED BY PULSED UV-LASER RADIATION - PART 2 - ALL-SILICA FIBERS WITH LOW-OH UNDOPED CORE

Up to now only high-OH fibers were suitable for pulsed W-laser applica tions, since low-OH material suffered from preexisting UV-absorbing co lour centers and excessive generation of these defects during UV-irrad iation. By loading commercial low-OH fused silica fibers with hydrogen , we were able to reduce the amount of initial absorption sites and to influence the generation of colour centers during irradiation. In our experiments we studied the transmission behaviour of hydrogen loaded low-OH fibers for 266 nm pulsed laser radiation. Spectroscopic experim ents explain many aspects of colour center creation and annealing and allow the determination of kinetic data for the underlying reactions. Based on this work it is possible to realize fiber optic beam delivery systems for special applications, where low-OH material shows superio r performance over high-OH material. (C) 1998 Elsevier Science B.V. Al l rights reserved.