Enhanced broadband near-infrared luminescence and its origin in Yb/Bi co-doped borophosphate glasses and fibers

•Broadband near-infrared emission from Yb/Bi co-doped borophosphate glasses and fibers was investigated.•The mechanism of Bi ions luminescence was discussed.•The infrared emissions pumped by 808 nm and 976 nm LDs were ascribed to Bi+ and Bi2+, respectively.

Yb/Bi co-doped borophosphate glasses and fibers were prepared. The effect of Yb3+ on the near-infrared (NIR) luminescent properties and the mechanism of luminescence of Bi-ions were investigated. Under 976 nm laser diode (LD) excitation, the NIR emission intensity of the glass with 8 mol% Yb2O3 co-doped glass is ~37 times stronger than that of Bi singly-doped glass. The fluorescence lifetime increases by ~7 times with 5 mol% Yb2O3 co-doped glass. The energy transfer efficiency is ~59.1%. It is also suggested that the broadband NIR luminescence pumped by 808 nm and 976 nm LDs derives from Bi+ and Bi2+, respectively.