UV And Gamma Induced Colour Centres In Germanium-Doped Silica Glass And Fibers

Abstract

Induced optical losses and paramagnetic Ge(n)-centres have been investigated in germanium doped silica glass and optical fibers after gamma- and UV-irradiation. It has been found that all the excitations created the similar effects. By means of selective photoexcitation Ge(1 and 3)-centres were identified in optical spectra presumably as the induced absorption bands at 4.4 eV and 6.2 eV, respectively. Moreover, for Ge(1)-centre photobleaching takes place under 266 nm excitation. In optical fibers we have observed no difference in ∝- and UV-induced loss spectra in the wavelength range from 480 nm to 1900 nm. We have found partial reversibility of the photo-colouration. The comparison of samples prepared by MCVD, VAD and PCVD techniques has been made. The origin of the dominant colour centres and their contributions to the irradiative induced losses are discussed.