Energy transfer and frequency upconversion in Pr3+-doped fluorophosphate glass

We have investigated the process of fluorescence quenching from the D-1(2) state of Pr3+ ions in fluorophosphate glasses of composition 60NaPO(3)-15BaF(2)-(25 - x)GdF3-xPrF(3) (x = 0.1, 0.2, 0.5, 1, 2, 5, and 10) (in mol%) due to energy transfer among Pr3+ ions. The fluorescence of the D-1(2) level is concentration quenched for Pr3+ concentrations >0.1 mol% even at 4.2 K. The non-exponential dependence of the decay from the D-1(2) level with increasing concentration, together with the dependence of the effective decay rates on Pr3+ concentration, indicates the presence of a dipole-dipole quenching process in the framework of a limited diffusion regime. Anti-Stokes emission from the P-3(0) level following excitation of the D-1(2) State is also observed. This anti-Stokes emission is attributed to upconversion by energy transfer. (C) 1999 Elsevier Science B.V. All rights reserved.