Er3+ ions doped bismuthate glasses sensitized by Yb3+ ions for highly. efficient 2.7 μm laser applications

In present study, we investigated the emissions from visible to mid-infrared and energy transfer processes in Er3+/Yb3+ co-doped germanate-gallate-bismuthate (BGG) glasses. Larger absorption cross-section of Yb3+ ions (7.5 x 10(-21) cm(2)) and enhanced up-conversion, near-infrared and mid-infrared emissions indicate that the introduced sensitized Yb3+ ions can efficiently absorb and transfer pumping energy (980 nm) to activate the Er3+ ions. The intensity of 2.7 mu m emission in Er3+/Yb3+ co-doped samples is about 3 times higher than that of Er3+ singly doped sample. But, the intensity of 2.7 mu m emission decreases with excessive Yb3+ ions. The optimized ratio of Er3+ and Yb3+ ions for 2.7 mu m emission is 1.0:0.2 in this BGG glasses. Large emission cross-section sigma(e) (-13 x 10(-21) cm(2) and -9.57 x 10(-21) cm(2) for 2.7 mu m and 1.5 mu m emissions, respectively) is obtained in Er3+/Yb3+ co-doped BGG glasses. According to absorption and emission spectra, energy transfer processes between Yb3+ and Er3+ ions were proposed and main reason for increased up-conversion is the strong excited state absorption (ESA) from excited Er3+ ions at I-4(11/2) and I-4(13/2) levels. Therefore, high pumping efficiency, intense emissions, large emission cross-section of 2.7 mu m and 1.5 mu m emissions and efficient energy transfer processes in this Er3+/Yb3+ co-doped BGG glasses hints its potential applications in laser materials, especially in 2.7 mu m wavelength. (C) 2013 Elsevier B.V. All, rights reserved.