Observation of defect-modulated photobleaching in bismuth-erbium co-doped fibers

The photobleaching (PB) phenomenon associated with silicon-related bismuth active centers (BAC-Si) in bismuth/erbium co-doped optical fibers (BEDFs) has been shown to significantly impact E-band gain characteristics. Extensive research has established a connection between the kinetics of PB and the defects associated with BAC-Si. To better understand the effect of defects on PB, different from the conventional direct ultraviolet laser irradiation, this work uses an 830-nm laser to excite BAC-Si to a metastable state initially, then uses a 248-nm excimer laser irradiation BEDF during the relaxation, and finally, is followed by a second PB process. Compared to directly irradiated BEDF, BAC-Si in a metastable state is more likely to receive or release charges. The experimental results indicate that the luminescence intensity of BAC-Si has decreased, while the PB effect has intensified after irradiation, a phenomenon associated with defect alterations induced by the 248-nm irradiation. This work provides experimental evidence that supports previous hypotheses regarding the generation of PB in BAC-Si. Additionally, it lays the groundwork for a more comprehensive understanding of the luminescence mechanism of bismuth.