Visible to infrared energy conversion in Pr3+-Yb3+ co-doped fluoroindate glasses

Processes involving visible to infrared energy conversion are presented for Pr3+-Yb3+ co-doped fluoroindate glasses. The emission in the visible and infrared regions, the luminescence decay time of the Pr3+:P-3(0) --> H-3(4) (482 nm), Pr3+:D-1(2) --> H-3(6) (800 nm), Yb3+:F-2(5/2) --> F-2(7/2) (1044 nm) transitions and the photoluminescence excitation spectra were measured in Pr3+ samples and in Pr3+-Yb3+ samples as a function of the Yb3+ concentration. In addition, energy transfer efficiencies were estimated from Pr3+:P-3(0) and Pr3+:D-1(2) levels to Yb3+:F-2(7/2) level. Down-Conversion (DC) emission is observed due to a combination of two different processes: 1-a one-step cross relaxation (Pr3+:P-3(0) --> (1)G(4); Yb3+:F-2(7/2) --> F-2(5/2)) resulting in one photon emitted by Pr3+ ((1)G(4) --> H-3(5)) and one photon emitted by Yb3+ (F-2(7/2) --> F-2(5/2)); 2-a resonant two-step first order energy transfer, where the first part of energy is transferred to Yb3+ neighbor through cross relaxation (Pr3+:P-3(0) --> (1)G(4); Yb3+:F-2(7/2) --> F-2(5/2)) followed by a second energy transfer step (Pr3+:(1)G(4) --> H-3(4); Yb3+:F-2(7/2) --> F-2(5/2)). A third process leading to one IR photon emission to each visible photon absorbed involves cross relaxation energy transfer (Pr3+:D-1(2) --> F-3(4); Yb3+:F-2(7/2) --> F-2(5/2)). (C) 2013 Elsevier B.V. All rights reserved.