The photo-bleaching of optical absorption bands in the 5eV region, and the creation of others at higher and lower energies, was studied in the case of the ArF (6.4eV) and KrF (5eV) excimer laser irradiation of 97SiO2-3GeO2 glass. It was reported that there was a difference in the transformation process of the neutral O monovacancy, and also of the Ge lone-pair center, into electron trap centers which were associated with 4-fold coordinated Ge ions and Ge-E' centers; depending upon which laser was used. Correlations between absorption bands and electron spin resonance signals were found after various stages of laser irradiation. It was found that the KrF laser generated twice as many Ge-E' centers as the ArF laser; for a given dose of delivered energy. The main reason for this difference was suggested to be the more efficient bleaching of the Ge lone-pair center (5.14eV) by the KrF laser, compared with the ArF laser.

Difference in the Behavior of Oxygen Deficient Defects in Ge-Doped Silica Optical Fiber Preforms under ArF and KrF Excimer Laser Irradiation. M.Essid, J.L.Brebner, J.Albert, K.Awazu: Journal of Applied Physics, 1998, 84[8], 4193-7