Photoinduced optical phenomena in silica fibers have received attention because of the demonstration of photoinduced second harmonic generation and photorefractive index gratings. For Ge doped fibers the mechanism responsible for both effects has been correlated with bleaching by UV irradiation of defects associated with the Ge ion. The effects of processing on UV bleaching of defects in high purity GeO2 have been examined. Bleaching kinetic studies indicate that processing variables such as melting temperature have a strong influence upon the bleaching of defects in GeO2 glasses.
Ion implantation of Cu in high purity silica has been used to produce nanometer size metallic copper clusters. The size and size distribution of these colloids have been characterized by quantitative images analysis emphasizing transmission electron microscopy. Electron diffraction patterns indicate they are crystalline FCC copper embedded in the amorphous silica host. The ion implantation dose and substrate temperatures alter the size distribution of the colloidal copper. The optical transmission of implanted silica containing varying sizes and size distributions of Cu clusters has been determined and is related to the size distribution.
We report the interaction of sub-band gap 5. 0 eV (KrF) laser irradiation with intrinsic defects in Type III and IV silica. The silicas were divided into two groups for laser interaction studies. One group was first irradiated with 137Cs to a dose of 6. 6 x iO?'' rads. The second group was irradiated with laser light in the as-received state. Optical absorptions of the samples from 3 to 6 eV were measured before and after 200 300 700 and 1500 pulses (l90mJ/pulse-cm2) of KrF laser light. Neither optical bands nor EPR spectra were observed in the as-received silicas. The spectra of samples pre-irradiated with 137Cs contained components due to peroxy radicals non-bridging oxygen hole centers E''centers and E" centers. The concentrations of these defects were dependent upon silica type. Subsequent laser irradiation of the gamma-ray irradiated samples bleached bands at 5. 4 and 4. 8 eV in type III and type IV silica respectively. The EPR spectra showed that laser irradiation bleached the peroxy radical and produced a new oxygen related center (ORC) in type IV silica. No detectable change in the non-bridging oxygen hole center concentration in the type III silica samples were observed. E'' center concentration increased. For the same laser irradiations the concentration of E'' centers produced in the as-received samples was a factor --''20 less than in the samples first irradiated with 137Cs. We suggest that