Energy transfer rates and population inversion investigation of (1)G(4) and D-1(2) excited states of Tm3+ in Yb:Tm:Nd:KY3F10 crystals

Author(s)

Linhares, Horacio Marconi da Silva M. D. ^[1] ; Henriques Librantz, Andre Felipe ^[2] ; Gomes, Laercio ^[1] ; Courrol, Lilia Coronato ^[3] ; Baldochi, Sonia Licia ^[1] ; Ranieri, Izilda Marcia ^[1]

Affiliation

^[1] IPEN CNEN SP, Ctr Lasers Aplicacoes, BR-05422970 Sao Paulo - Brazil

^[2] Univ Nove de Julho, UNINOVE, Dept Ciencia Exatas, BR-02111030 Sao Paulo - Brazil

^[3] Univ Fed Sao Paulo, UNIFESP, Dept Ciencias Exatas & Terra, BR-09972270 Sao Paulo - Brazil

• Document type: Journal article
• Source: Journal of Applied Physics; v. 109, n. 8 APR 15 2011.
• Web of Science Citations: 4

Abstract

In this work we present the spectroscopic properties of KY3F10 (KY3F) single crystals activated with thulium and co-doped with ytterbium and neodymium ions. The most important processes that lead to the thulium up-conversion emissions in the blue and ultraviolet regions were identified. A time-resolved luminescence spectroscopy technique was employed to measure the luminescence decays and to determine the most important mechanisms involved in the up-conversion process that populates (1)G(4) and D-1(2) (Tm3+) excited states. Analysis of the energy-transfer processes dynamics using selective pulsed-laser excitations in Yb:Tm:Nd, Tm:Nd, and Tm:Yb KY3F crystals show that the energy transfer from Nd3+ to Yb3+ ions is the mechanism responsible for the enhancement of the blue up-conversion efficiency in the Yb:Tm:Nd:KY3F when compared with the Yb:Tm system. A study of the energy transfer processes in Yb:Tm:Nd:KY3F crystal showed that the (1)G(4) excited level is mainly populated by a sequence of two nonradiative energy transfers that starts well after the Nd3+ and Tm3+ excitation at 797 nm according to:Nd3+ (F-4(3/2)) -> Yb3+ (F-2(7/2)) followed by Yb3+ (F-2(5/2)) -> Tm (H-3(4)) -> Tm3+ ((1)G(4)). Results of numerical simulation of the rate equations system showed that a population inversion for 483.1 nm laser emission line is attained for a pumping rate threshold of 98 s(-1), which is equivalent to an intensity of 3.3 KW cm(-2) for a continuous laser pumping at 797 nm for Yb(30 mol%):Tm(0.5 mol%):Nd(1 mol%):KY3F. Nevertheless, best Yb3+ concentration for the laser emission near 483.1 nm was estimated to be within 40 and 50 mol%. On the other hand, a population inversion was not observed for the case of 960 nm (Yb3+) pumping. (C) 2011 American Institute of Physics. {[}doi:10.1063/1.3552924] (AU)