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NN5.4.1

Luminescence and Upconversion Dynamics of Praseodymium in LiLuF4 Laser Crystals Gönül Özen1, 4; John M Collins2; Ottavio Forte1; Misha Meylman1; R. Yu Abdulsabirov3; Baldassare Di Bartolo1. 1 Department of Physics, Boston College, Chestnut Hill, MA, USA. 2 Department of Physics and Astronomy, Wheaton College, Norton, MA, USA. 3 Laboratory of Quantum Electronics and Radiospectroscopy, Kazan State University, Kazan, Russian Federation. 4 Department of Physics, Istanbul Technical University, Istanbul, Turkey. ABSTRACT We have investigated the spectroscopic properties of Pr3+ ions in LiLuF4 laser host doped with 0.5% Pr3+ ions as a function of temperature. We obtained the luminescence spectra by exciting selectively the sample at 439nm into the 3P2 level and at 593nm into the 1D2 level. With excitation in the 3P2 level we obtained emission only from the 3P0 level but not from the 1D2 level at all temperatures between 24 and 300K. With excitation into the 1D2 level we observed the luminescence emitted by the same level and a strong blue up-conversion emission from the 3P0 level. We used the decay pattern inspection to assign spectral lines to specific radiative transitions and to study the dynamics of the excited ions in the crystal. Under direct excitation, the 1D2 decay curve is nonexponential at all temperatures, whereas the 3P0 decay is exponential only at low temperatures. The experimental data indicate that the 3P0 level is populated via upconversion due to mainly energy transfer.

INTRODUCTION Rare-earth doped crystalline solids are very attractive because of their important applications in lasers and non-linear optics[1]. In particular, praseodymium (Pr3+) in various crystals has been widely studied because of its energy level structure and suitable lifetimes of the meta-stable levels in 4f 2 configuration [2-5]. Praseodymium, in general, enters solid host lattices in its trivalent state. There are at least two potentially useful transitions associated with emissions in the 600nm region: the 1D2 to 3H4 transition and the 3P0 to 3H6 transition. Previous studies of Pr doped LiLuF4 crystals concentrated on the basic optical and spectroscopic properties such as the position of the energy levels of the Pr3+ ions in 4f 2 configuration and 4f 2 to 4f5d excited state absorption [6, 7]. LiLuF4: Pr has also exhibited laser action, as documented by Kaminskii [1]. Besides the practical applications of praseodymium doped crystals there are some interesting basic processes such as multi-phonon relaxations and up-conversion processes that need to be explored. The electronic configuration of Pr3+ is [(closed shell)+4f 2]. The total number of the 4f 2 states is 91. The electron-electron interaction creates the LS terms 3H, 3F, 1G, 1D, 1I, 3P, and 1S. The lowest term is 3H in accordance with Hund’s rule. The spin-orbit interaction splits each LS term into J sublevels and mixes states with the same J numbers from different terms. Because of this term-mixing there are departures from the Landé internal rule. The J levels ar