Effect of hydroxyl groups on Er3+-doped bismuth-borate glass and fiber

A series of Er3+-doped Bi2O3–B2O3–GeO2–Na2O glasses with different OH− group contents were prepared and the interactions between Er3+ ions and OH− groups were investigated. The observed increase of the fluorescence intensity and decaying variation from an evident non-exponential to a nearly exponential behavior of the Er3+:4I13/2 level with the oxygen gas bubbling time was related to the reduction of the OH− group contents evidenced by infrared (IR) absorption spectra, which demonstrated that the OH− groups were dominant quenching centers of the excited Er3+. Meanwhile, by reducing the OH− group contents in the fiber cores with the same glass composition, the simulated gain characteristics improved dramatically and a 12.4 dB gain at 1560 nm was achieved in a 20 cm fiber with 150 mW pumping power at 980 nm.