Defect population in Ge doped silica studied by fluorescence spectroscopy.

The interest for Ge doped SiO2 properties is revived by the search of optimisation of photorefractivity. The first step of the mechanism is an absorption at around 240-250 nm or 193 nm. Next step of the transformation leads to index change . Whatever it is connected to a special defect or not, the study of the defect population increases our understanding on that subject and for other applications (fiber line attenuation, nonlinear effect). In this paper, we show that UV spectrum of MCVD doped silica is composed of several gaussian components which appear at the same position and with the same width but varie in intensity depending on the samples. We try to systematize this population.