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Bismuth-doped germanate glasses,as compared to rare-earth doped glasses,hold promise for super-broadband near-infrared(NIR)photoemission and potential applications in optical amplification.However,optically active bismuth centers are extremely sensitive to the properties of the surrounding matrix,and also to processing conditions.This is strongly complicating the exploitation of this class of materials,because functional devices require a very delicate adjustment of the redox state of the bismuth species,and its distribution throughout the bulk of the material.It also largely limits some of the conventional processing routes for glass fiber,which start from gas phase deposition and may require very high processing temperature.Here,we investigate the influence of melting time and alkali addition on bismuth-related NIR photoluminescence from melt-derived gerrmanate glasses.We show that the effect of melting time on bismuth-related absorption and NIR photoemission is primarily through bismuth volatilization.Adding alkali oxides as fluxing agents,the melt viscosity can be lowered to reduce either the glass melting temperature,or the melting time,or both.At the same time,however,alkali addition also leads to increasing mean-field basicity,what may reduce the intensity of bismuth-related NIR emission.Preferentially using Li2O over Na2O or K2O presents the best trade-off between those above factors,because its local effect may be adverse to the generally assumed trend of the negative influence of more basic matrix composition.Beyond qualitative descriptions,quantitative empirical prediction laws are established on the grounds of relationships between compositions,structures and properties of bismuth-doped germanate glasses.We believe these works are helpful to design melt-derived Bi-doped glasses and fibers with efficient NIR photoemission and high optical homogeneity in the future.