Crystal growth, upconversion, and infrared emission properties of Er 3+-doped KPb2Br5

We report on the material preparation and optical properties of Er3+-doped KPb2Br5 (KPB), KPB has a maximum phonon energy of only 138 cm(-1) and is non-hygroscopic. which makes KPB in attractive candidate for solid-state laser applications. The preparation of Er doped KPB was based on a careful purification of starting materials followed by self-seeded Bridgman crystal growth. Under 975 nm diode laser pumping, ErKPB revealed intense blue upconversion emission. For comparison, Er-doped KPb2Cl5 (KPC), which has a maximum phonon energy od 203 cm(-1) exhibited a dominant green Er 31 upconversion emission, The blue upconversion from ErKPB can be attributed to emission from the F-4(7), excited state of Er3+, which is quenched in most solid hosts due to strong multiphollon non-radiative decay. Due to the small phonon energy of KPB, the F-4(72) level becomes highly radiative with a room-temperature lifetime of similar to 85 mu s and an estimated quantum efficiency of similar to 94%. For comparison, the F-4(72) decay time in ErKPC was only -11 mu s at room temperature and the radiative quantum efficiency was estimated to be similar to 9%. Infrared (IR) emission bands were observed at 1.5 mu m (I-4(132) -> I-4(152)). 1.7 mu m (I-4(92) -> I-4(132)), 2.0 mu m (F-4(92) center dot I-4(132)), 2.7 mu m (I-4(112) -> I-4(13/2)), 3.6 mu m (F-4(92) -> I-4(92)) and 4.5 mu m (I-4(92) -> I-4(112)), indicating the potential of Er:KPB for IR laser applications. The absorption and IR emission properties of Er:KPB were investigated in terms of transition linestrengths, branching ratios, radiative decay rates, and emission cross-sections Using the Judd Ofelt method. (c) 2004 Elsevier B.V. All rights reserved.