  We studied the optical absorption induced by 4.7eV pulsed laser radiation on
Ge-doped a-SiO2 synthesized by a sol-gel technique. The absorption spectra in
the ultraviolet spectral range were measured during and after the end of
irradiation with an in situ technique, evidencing the growth of an absorption
signal whose profile is characterized by two main peaks near 4.5eV and 5.7eV
and whose shape depends on time. Electron spin resonance measurements performed
ex situ a few hours after the end of exposure permit to complete the
information acquired by optical absorption by detection of the paramagnetic
Ge(1) and Ge-E' centers laser-induced in the samples.
