Fully recoverable fiber lasers under radiation enabled by <i>in-situ</i> blue light photobleaching

Fiber lasers are increasingly employed in radiative environments, such as outer space and nuclear facilities. However, their performance is significantly compromised under irradiation due to the accumulation of defects in fiber components. Despite various radiation-hardening strategies, including optimized fiber designs and post-treatment techniques, these approaches have been unable to fully mitigate performance degradation. In this study, we demonstrate near 100% power recovery in a 150 W fiber laser exposed to radiation, achieved through an in-situ photobleaching technique utilizing low-power blue light. This all-fiber photobleaching strategy not only restores laser performance but also provides a robust, compact, and scalable solution for developing high-performance radiation-resistant fiber lasers. The proposed approach holds significant potential for advancing laser applications in challenging radiative environments, such as space exploration, nuclear power plants, and medical radiotherapy.