Solution Strategy for High Gain Glass Fiber and MHz Mode‐Locked Laser

The advancement of Er‐activated fiber holds significant implications for applications in scientific and industrial domains such as optical fiber communication, precision measurement, and advanced manufacturing. It strongly relies on the performance of the Er‐doped active material, and a candidate with both high gain and robust mechanical properties is urgently required. Herein, a solution strategy for the development of heavily Er‐activated high‐gain silicate fiber and laser devices is proposed. Theoretical and experimental studies reveal that the incorporation of the inert rare‐earth ions provides a unique environment for the dispersion of Er3+ ions, thus greatly enhancing their radiative transition efficiency. In addition, a heavily Er‐activated silicate glass fiber (ESGF) hybridized with inert rare‐earth is designed and fabricated. It possesses excellent gain response with a net gain coefficient of ≈2.12 dB cm−1, which is the highest gain coefficient among the Er‐activated silicate fiber ever reported. Furthermore, utilizing a 3.8‐cm‐long ESGF, an all‐fiber‐integrated passively mode‐locked fiber laser device is successfully constructed, with a fundamental frequency repetition rate of 73 MHz and a spectral bandwidth of 12.46 nm. These findings are believed to bring new strategies for the exploration of advanced rare‐earth glass fiber materials and devices.