Modulating broadband near infrared emission from Bi doped borate laser glass by codoping nonactive rare earth ions

•A series of Bi and nonactive rare earth (RE) codoped aluminoborate glasses were prepared and systematically investigated.•The effect of nonactive RE on aluminoborate glasses structure and optical basicity was determined.•When discussing the energy transfer between optical centers with multiple valences and RE ions (such as Bi, Mn and Cr), the effect of RE on glass structure and optical basicity should be considered. Bismuth (Bi) doped glasses and fibers, as a new generation of gain media, have been drawing wide attention for the super broad and long lived near infrared (NIR) emission. Yet, great challenge exists for modulating the Bi NIR emission in multi-component glasses. Codoping rare earth ions is a feasible way to modulate the NIR emission properties of Bi, yet limited success have been achieved. Here, to provide deeper understanding on Bi-RE codoped glass, we prepared a series of Bi and nonactive rare earth (RE) codoped aluminoborate glasses and systematically investigated the optical and structure properties. Evidenced by detailed structural and optical characterizations, it is found that the addition of nonactive RE ions changes the glass structure and optical basicity, so as to alter the optical properties of Bi. These results indicate that one should consider the effect of codopant on glass structure and optical basicity when modulating the optical spectra of active ions based on energy transfer, especially for those with multiple valences.