Spectroscopic properties of Er3+-doped lithium-modified bismuth tellurite glasses for broadband near-infrared emission

E3+ ions doped tellurite glasses are very attractive for laser and photonic applications. In this work, the glass forming ability of bismuth tellurite glasses was investigated by adding Li2O, and an optimal glass stability was obtained with additional dopant of 8 mol% Li2O. Moreover, an intense near-infrared (NIR) emission at 1.5 mu m was observed in Er3+-doped TeO2-Bi2O3-Li2O (TBL-xEr) glasses with the full width at half maxima (FWHM) from 76 to 114 nm. 2.7 mu m and visible emissions were also measured to understand the competitive luminescent mechanism. The maximum emission intensity at 1.5 mu m was observed in TBL-1.0Er, while it decreased as the Er2O3 concentration continued to increase due to energy transfer between I-4(11/2) and I-4(13/2) level. Furthermore, Judd-Ofelt theory was used to evaluate the spectroscopic characteristics including radiative transition probability, branching ratio and radiative lifetime of Er3+ ions through absorption spectra. Glass TBL-1.0Er presented a large calculated stimulated emission cross-section (sigma em) at around 1.5 mu m (10.43 x 10(-21) cm(2)) and a high quantum efficiency (76.16%). Hence, these results imply that the developed glasses are promising gain-medium candidates for broadband optical amplifiers.