Photosensitivity of germanium-doped multicomponent silicate glasses: role of boron and sodium ions

Photosensitive, germanium-doped multicomponent silicate glasses were prepared and submitted to electron paramagnetic resonance measurements. Spectral data were recorded before and after UV excimer laser irradiation at an emission wavelength of 248 nm at various energy doses. A particular attention was devoted to the analysis of defect signal intensities and characteristics, by performing saturation plots, intensity decay spectra versus time and temperature, with the aim of studying the structural changes involved in laser irradiation, which lead to a refractive index change, exploited for telecom and sensor applications. The main results showed that the presence of boron and the absence of sodium play a role in the type and the number of defects, their time and thermal decay, always keeping constant the UV exposure of the glasses. Consequently, the presence, the absence and the co-presence of these two ions may have a role in the photosensitivity of the glasses. It is important to understand the role of both, particularly the role of sodium on the photosensitivity of germanosilicate and germano-boro-silicate glasses, for their interest in the field of ion-exchangeable glasses for photonic waveguides and Bragg-grating based devices.