Energy transfer process and Tb 3+ up-conversion luminescence in Nd 3+–Yb 3+–Tb 3+ co-doped fluorozirconate glasses

Abstract

Up-conversion properties and energy transfer processes in Nd 3+, Yb 3+ and Tb 3+ co-doped ZrF 4-based fluoride glasses have been studied under 800 nm light excitation. Blue (490 nm), green (545 nm), yellow (580 nm) and red (624 nm) up-converted emissions which can be assigned to the Tb 3+ : 5 D 4→ 7 F J ( J=6, 5, 4 and 3) transitions, respectively, were strongly observed. Among the Nd 3+, Yb 3+ and Tb 3+ ions, only Nd 3+ has a ground state absorption due to the ( 2 H 9/2, 4 F 5/2)← 4 I 9/2 transitions which can be directly pumped by 800 nm radiation. Therefore, a possible up-conversion mechanism is proposed as follows: At first, Nd 3+ is excited by 800 nm light, followed by the energy transfer from Nd 3+ to Yb 3+, and finally “co-operative energy transfer” occurs between two excited state Yb 3+ and one ground state Tb 3+. It was also demonstrated that the energy back-transfer from Tb 3+ to Nd 3+, causing quenching of up-conversion luminescence.