Photobleaching of photodarkening in ytterbium doped aluminosilicate fibers with 633 nm irradiation

In the present study, we examined photodarkening loss reduction in Yb3+ doped aluminosilicate fibers by utilizing 633 nm light irradiation. It is demonstrated that the final photobleaching value is intensity dependent, but the percentage of photodarkening reduction does not depend on dopant concentrations for settled bleaching intensity. Further examination was committed to explore the photobleaching starting from different photodarkening loss levels while keeping the same dopant concentration and subsequently the other way around. This approach related photobleaching with the number of photodarkening induced color centers and also showed that photobleaching was dopant concentration dependent. In all experiments an unbleachable residual loss for the bleaching powers up to ~100 W/mm2 was found. To the best of our knowledge this is the most extensive investigation of photobleaching effect.