Abstract

SiO₂:Ge(10 %) glasses prepared by the vapor phase deposition were exposed tp ultraviolet radiation from a filtered Hg discharge lamp ( 4.9 eV )and excimer lasers ( ArF : 6.4 eV, KrF : 5.0 eV, and XeCl 4.0 eV). Two photochemical reaction channels were ascertained : (1) The exposure to the lamp irradiation ( ~ 16 mW/cm²) induced Ge E' centers accompanied by bleaching of the absorption component (peaking at 5.06 eV) due to the neutral oxygen monovacancies ( NOMV ) and emergence of an intense band near 6.4 eV and a shoulder at around 5.7 eV. (2) Irradiation with the excimer lasers ( pulse duration; 20 ns ) generated two types of paramagnetic defects, electron trapped centers ( GEC)¹ associated with four-fold coordinated two Ge ions or a Ge ion and a Si ion and a self-trapped hole center ( STH: bridging oxygen trapping a hole )². The striking difference in induced ESR centers are evident in fig. 1. The former and the latter were concluded to be caused via one-photon and two-photon absorption processes ( an example indicating 2-photon process is shown for ArF laser in fig.2), respectively.

© 1995 Optical Society of America