Preparation And NIR Luminescence Properties Of Bismuth-doped Borate Laser Glass

Bismuth doped gain materials display an ultra-wideband near-infrared emission spanning the spectral range of 1000 to 1600 nm,which can cover the entire low-loss communication window of the silica fiber.The bismuth-doped materials appear to be promising gain materials for the applications of ultra-wideband fiber amplifiers.However,the existing bismuth-doped silica optical fibers must be fabricated at high temperature(more than 2000?),which would cause severe volatilization of bismuth,and leave extremely low residual amount of bismuth(~50ppm)in the optical fibers.Therefore,in this work,we chose bismuth-doped borate glasses as the research object,which could be prepared at relatively low temperature of 1400-1450?.The maximal doping concentration of Bi2O3 was up to 6mol%.Besides,we proposed a strategy to enhance and tune the bismuth NIR luminescence properties,the specific results obtained are as follows:(1)The bismuth-doped borate glasses with different alkaline-earth metal species and contents were prepared systematically at 1400?.The influence of alkaline earth metal concentrations and species on the bismuth NIR luminescence properties were studied.Combinating the analyses of structure characterization of FT-IR and NMR with optical basicity of glass system calculated,the qualitative relationship between the NIR emission peak position and the optical basicity was obtained,ie,the increasing of optical basicity in the glass system leads to redshift,and vice versa.Simultaneously,we obtained the relationship between the NIR emission intensity and the B-O,Al-O polyhedral units in the glass network structure,namely the BO4 and AlO5 in the borate-based glass network structure favor the bismuth NIR emission.The influence of BO4 maintain dominant role at low Al2O3 concentrations(less than 6mol%),while the role of AlO5 will surpass over BO4 with further increasing Al2O3 concentrations(2)The bismuth-doped borate glasses with different Bi2O3 and Y2O3 concentrations were prepared systematically at 1400?.The influence of doping concentrations of Bi2O3 and Y2O3 on the bismuth NIR luminescence properties were studied.The optimal glass composition of 77B2O3-15CaO-5Al2O3-3Y2O3-6Bi2O3 was obtained,subsequently,we tested the emission performance at different temperature.The glass sample still showed quite excellent thermal stability of NIR luminescence properties after several thermal cycling tests.(3)The bismuth-doped borate glasses with different different GeO2 concentrations were prepared systematically at 1450?.We expected to improve the homogeneity and stabilize the bismuth NIR luminescence by adding GeO2 into the bismuth-doped borate glasses.We can obtain homogenous and transparent bismuth-doped glass samples with B2O3 and GeO2 at relatively low preparing temperature(1450?).We found that the bismuth NIR emission would be broadened and enhanced,as well as the absorption coefficience could be enhanced when increasing the GeO2 content.On the base of systematical and scientific structure characterization of NMR,Ranman and FT-IR,we found Ge ions and B ions could form the glass network together,which resulted in the generation of new bismuth emission centers.The AlO5 and AlO6 species would gradually transfer into AlO4 species by increasing the GeO2 concentrations from 0mol% to 67mol%,which could favor the bismuth NIR luminescence,that's why the enhancement of both absorption coefficience and NIR emission intensity of the glass samples could be observed.