As well known, so far most of works about 2.7？μm emission materials have been done in fluoride (ZBLAN) glasses. The glass family is the most stable one among all fluoride systems reported so far. In the past decade, Er doped and Er/Pr co-doped ZBLAN fibers have been developed for obtaining higher power output. But, the T_g of the ZBLAN is as low as 270°C which causes thermal effect. Additionally, because of the small value of DT, crystallization is an obstacle of fabricating high concentration ZBLAN fibers. These weaknesses limit the application of the ZBLAN in the future. So it is important and challenging for researcher to find new mid-infrared materials.However, no works concern near to middle infrared emissions of Er³⁺/Yb³⁺ doped fluorotellurite glass excited under different wavelengths.

Researchers in Prof.HU Lili’s group of Shanghai Institute of Optics and Fines Mechanics (SIOM), Chinese Academy of Sciences , reported the near to middle infrared luminescence and energy transfer process of Er³⁺/Yb³⁺ co-doped fluorotellurite glasses under 980, 1550 and 800？nm excitations, respectively. Using a 980？nm laser diode pump, they observed enhanced 1.5 and 2.7？μm emissions from Er³⁺:I_13/2→⁴I_15/2 and I_11/2→⁴I_13/2 transitions, in which Yb³⁺ ions can increase pumping efficiency and be used as energy transfer donors.

Meanwhile, Yb³⁺ used as an acceptor and intensive upconversion luminescence of around 1000？nm was achieved from Er³⁺:I_11/2→⁴I_15/2 and Yb³⁺: F_5/2→⁴F_7/2 transitions using 1550？nm excitation. In addition, the luminescence properties and variation trendency by 800？nm excitation was similar to that using 1550？nm excitation. The optimum Er³⁺ and Yb³⁺ ion ratio was 1:1.5 and excess Yb³⁺ ions decrease energy transfer efficiency under the two pumpings. These results indicated that Er³⁺/ Yb³⁺ co-doped fluorotellurite glasses were potential middle- infrared laser materials and may be used to increase the efficiency of the silicon solar cells.

This study was published on Scientific Reports on Feb.4, 2015.[ http://www.ncbi.nlm.nih.gov/pubmed/25648651] This research was supported by the Chinese National Natural Science Foundation.