DIFFERENCE IN THE BEHAVIOR OF OXYGEN-DEFICIENT DEFECTS IN GE-DOPED SILICA OPTICAL-FIBER PREFORMS UNDER ARF AND KRF EXCIMER-LASER IRRADIATION

Photobleaching of optical absorption bands in the 5 eV region and the creation of others at higher and lower energy have been examined in th e case of ArF (6.4 eV) and KrF (5 eV) excimer laser irradiation of 3Ge O(2):97SiO(2) glasses. We report a difference in the transformation pr ocess of the neutral oxygen monovacancy and also of the germanium lone pair center (GLPC) into electron trap centers associated with fourfol d coordinated Ge ions and Ge-E' centers when we use one or the other l aser. Correlations between absorption bands and electron spin resonanc e signals were made after different steps of laser irradiation. It was found that the KrF laser generates twice as many Ge-E' centers as the ArF laser for the same dose of energy delivered. The main reason for this difference is found to be the more efficient bleaching of the GLP C (5.14 eV) by the KrF laser compared to that by the ArF laser. (C) 19 98 American Institute of Physics. [S0021-8979(98)06220-3].