Enhanced 1.8 mu m emission in Yb3+/Tm3+ co-doped tellurite glass: Effects of Yb3+ <-> Tm3+ energy transfer and back transfer

The similar to 1.8 mu m emission characteristics of Tm3+ by a direct excitation and through an energy transfer process upon sensitization with Yb3+ ions in tellurite glass are reported. The spectroscopic properties of Tm3+ ions have been evaluated by applying Judd-Ofelt theory on the measured absorption spectrum. The obtained intensity parameters, Omega(2)=7.155 x 10(-20) cm(2), Omega(4)=3.325 x 10(-20) cm(2), Omega(6)=1.278 x 10(-20) cm(2) are used to estimate the radiative properties of Tm3+ ions in the present glass host. A similar to 10 fold enhancement in the Tm3+ 1.8 mu m emission observed with 16 fold reduced emission of Yb3+ ions (1008 nm) in co-doped sample on Yb3+ ions excitation illustrates the efficient energy transfer from Yb3+: F-2(5/2)-> Tm3+: H-3(5). The energy transfer process assisted by host phonon energy has been discussed by using relevant theoretical models and estimated the energy transfer micro-parameters. Effect of energy back transfer Tm3+-> Yb3+ on NIR and upconversion emissions have been discussed. An efficient similar to 1.8 mu m with comparatively higher emission cross-section 1.115 x 10(-20) cm(2) on account of reduced upconversion emissions has been achieved in the present tellurite glass. (C) 2014 Elsevier Ltd. All rights reserved