Highly efficient blue up-conversion of Tm 3+ in Nd 3+–Yb 3+–Tm 3+ co-doped ZrF 4-based fluoride glass

Abstract

Up-conversion luminescence and energy-transfer processes in Nd 3+, Yb 3+ and Tm 3+ co-doped ZrF 4-based fluoride glasses have been studied under 800 nm light excitation. Blue up-converted emission around 478 nm which can be assigned to the Tm 3+: 1 G 4→ 3 H 6 transition, was strongly observed. Up-conversion luminescence intensity exhibited an YbF 3-concentration dependence. Among the Nd 3+, Yb 3+ and Tm 3+, Nd 3+ and Tm 3+ have ground state absorption bands due to the ( 2 H 9/2, 4 F 5/2)← 4 I 9/2 and 3 F 4← 3 H 6 transitions, respectively, which can be directly pumped by 800 nm radiation. However, no emissions were observed in Tm 3+ singly-doped and Tm 3+–Yb 3+ doubly-doped glasses under 800 nm excitation. Therefore, a possible up-conversion mechanism may be proposed as follows: energy-transfer firstly occurs from Nd 3+ to Yb 3+ when Nd 3+ is excited by 800 nm light, then the energy is transferred from Yb 3+ to Tm 3+ which is in the excited state and, finally, blue up-conversion emission of Tm 3+ is observed through the Tm 3+: 1 G 4→ 3 H 6 transition.