Ultrabroad NIR luminescence and energy transfer in Bi and Er/Bi co-doped germanate glasses

The effects of temperature, pump power and excitation wavelength on near-infrared photoluminescence from Bi-doped multi-component germanate glasses are presented. Compared to conventional silica/silicate matrices, the examined material exhibits superior resistance to thermal quenching and less pronounced excited state absorption for pumping at 808 nm. It is shown that by selecting the optimal excitation wavelength, photoemission can be initiated from multiple active centers in parallel, resulting in an emission bandwidth (full width at half maximum) of more than 370 nm. Er3+/Bi co-doping is presented as an effective means to significantly enhance emission intensity around 1.5 μm by suppressing the typical Er3+-related red-to-green upconversion. Besides its relevance for Bi-doped materials, this also indicates a new route towards improving the performance of Er-based optical devices. The mechanism of Er3+→Bi energy transfer is examined in detail. Adjusting the molar ratio between both species provides an effective tool for tuning the emission scheme and further increasing emission bandwidth.