Defect formation in SiO2:GeO2glasses studied by irradiation with excimer laser light

The formation of germanium electron centers in ${\left[\mathrm{S}\mathrm{i}{\mathrm{O}}_2\right]}_9$[Ge${\mathrm{O}}_2$] glasses by irradiation with excimer laser light was found to occur via two-photon absorption processes for ArF, KrF, and XeCl lasers. Although the wavelength of KrF laser light corresponds to the absorption band of preexisting oxygen-deficient defects associated with Ge ions, no significant difference in the formation efficiency was seen between ArF and KrF laser lights. The efficiency for XeCl laser light was smaller by four orders of magnitude than that for ArF or KrF light, but was still larger by an order of magnitude than the formation efficiency of Si $E^{\prime }$ centers in Si${\mathrm{O}}_2$ glasses with ArF laser light. It was shown that defect-formation efficiencies for the case where the two-photon energy is close to the optical band gap are much lower than for that when the two-photon energy is enough to exceed the band gap.