The Bulk Crystal Growth and Yellow-Orange Spectral Performances of Pr3+: Baf2 and Pr3+/Re3+(Re3+ = Gd3+, Y3+, Lu3+, Ce3+): Baf2 Crystals

Abstract

Single crystals of 0.6 at.% Pr3+: BaF2 and 0.6 at.% Pr3+/1.2 at.% RE3+ (where RE3+ = Gd3+, Y3+, Lu3+, and Ce3+) were synthesized using the Bridgman-Stockbarger technique. Comprehensive characterizations, including absorption, visible emission, and fluorescence decay properties, were performed. Moreover, based on their excitation and emission spectra, decay curves of Pr3+: BaF2 and Pr3+/RE3+: BaF2 crystals were recorded at a low temperature of 77 K. Our investigations revealed that Pr ions occupy at least three distinct lattice positions within BaF2 crystal matrix. Co-doping agents, such as Gd3+, Y3+, or Lu3+, effectively reduce the lattice positions occupied by Pr3+ ions. Analysis of the absorption spectra indicated an increased absorption cross-section when co-doped with Gd3+, Y3+, and Lu3+, reaching a maximum of 1.69x10 -20 cm2. In contrast, when co-doped with Ce3+, the absorption bandwidth expanded to 15 nm. Examination of the visible fluorescence spectra revealed that co-doping with Gd3+ amplified yellow-orange light emission by 12 times, with Y3+ by 8 times, and with Lu3+ by 9 times. This enhancement became more pronounced as the concentration of the co-dopants increased. When co-doped with Ce3+, both the emission bandwidth (24.82 nm) and fluorescence lifetime (244 μs) doubled. Overall, both singly-doped and co-doped Pr: BaF2 crystals demonstrated wider emission peak widths and longer fluorescence lifetimes compared to other Pr3+-doped crystals.

Keywords: Yellow-orange laser, BaF2 crystal, Pr3+, Lattice sites, Fluorescence, Co-doping