Effect of irradiation temperature on the radiation induced attenuation of Ge-doped fibers

The UV-visible radiation induced attenuation (RIA) was studied in Ge-doped optical fibers, during X-ray (10 keV) irradiations at different temperatures. By comparing the spectra recorded in dissimilarly irradiated samples we evidenced the impact of the irradiation temperature. In details, we highlighted that, from a certain dose, increasing the temperature the RIA decreases for wavelengths lower than 470 nm, whereas at higher wavelengths the RIA depends only on the dose. Such findings suggest that it is possible to distinguish the irradiation temperature by comparing the signal at two different wavelengths. From the microscopic point of view, it appears that the RIA behavior is mainly related to a dissimilar content of induced Ge(1) defects, whereas the so called GeX defects features only small variations. The impact of the irradiation temperature on the Ge(1) induced concentration, as a function of the irradiation temperature, is confirmed by the post-irradiation electron paramagnetic resonance measurements that we acquired for samples that were irradiated at room temperature and at 200 degrees C.