L Journal of Alloys and Compounds 300–301 (2000) 430–434 www.elsevier.com / locate / jallcom 3 1 Energy transfer processes in Pr : Be La O crystals 2 2 5 * R. Piramidowicz , M. Kowalska, M. Malinowski Institute of Microelectronics and Optoelectronics PW , ul. Koszykowa 75, 00-662 Warsaw, Poland Abstract 31 Up-converted blue emission has been generated in a 1 at.% Pr :Be La O crystal after orange and infra-red excitation. The 2 2 5 responsible up-conversion mechanisms were investigated and shown to be energy transfer and excited state absorption, respectively. The 31 dynamics of the involved excited states have been studied under pulsed laser excitation. These results are compared with those for Pr ion in different laser crystals.  2000 Elsevier Science S.A. All rights reserved. 31 Keywords: Praseodymium; Pr :Be La O ; Luminescence; Up-conversion 2 2 5 1. Introduction 2. Experimental Lanthanum beryllate crystals Be La O (BLO) doped The experimental apparatus used to investigate spectro- 2 2 5 31 by lanthanide ions have been recently investigated as scopic properties of Pr ion in Be La O has been 2 2 5 potential laser systems. Neodymium doped BLO was described previously [9]. shown to have a good lasing properties [1], holmium doped BLO was investigated as the potential 3-mm laser 2.1. Orange-to-blue wavelength up-conversion material [2] and polarized optical spectra and TR ESA have been measured in BLO:Pr [3]. In [4] we have 1 It was observed that excitation of the D Stark levels 2 reported the absorption, emission, excitation and fluores- 3 results in an intense emission from the higher lying P 0 cence lifetime measurements for sample containing 1 at.% state. The excitation spectrum of this anti-Stokes up-con- 31 of Pr ions. We presented also a Judd–Ofelt analysis of verted emission in the Be La O crystal, presented in Fig. 31 2 2 5 the Pr ion oscillator strengths in BLO. 3 1, was recorded when collecting the P fluorescence at 31 0 Trivalent praseodymium ion (Pr ) in various crystals is 491 nm and tuning the laser frequency over the lowest well known for having a very rich emission spectrum 1 21 Stark component of the D manifold at 16 500 cm (606 2 extending from the ultra-violet (UV) to the infra-red (IR) 1 nm). For comparison the excitation spectrum of the D 2 [5,6]. Because of the energy level structure, and suitable 1 emission, measured by monitoring the D near IR fluores- 31 2 lifetimes of the excited states, Pr systems are also cence, is also displayed in the same figure. It is seen that attractive as short wavelength up-conversion laser materi- differences between the shape of the excitation profiles als [7]. Recently, simultaneous blue and orange wave- 3 exist. The temporal evolution of the P Stokes and anti- 31 0 length lasing in Pr doped YAG,YAP and YLF crystals Stokes emissions are presented in Fig. 2. It can be seen has been studied [8] and observation of lasing at 486 nm in that the up-converted signal has a short rise time of 0.2 ms 31 Pr :GGG has been also reported [8]. and decay is non-exponential, approaching at long time This encouraged us to study possible up-conversion delays the decay time of 2 ms which is nearly equal to the 31 processes of Pr ion in Be La O . In this work we 3 2 2 5 P fluorescence decay time measured under OP excitation 0 analyze up-conversion processes leading to blue fluores- conditions. 3 31 cence from the excited P state of the Pr ion in 0 Be La O crystal. We report the IR-to-blue and orange-to- 2 2 5 2.2. IR-to-blue wavelength up-conversion blue wavelength up-conversion. Blue and several transitions in the visible part of the *Corresponding author. Tel.: 148-22-660-7783; fax: 148-22-628- 3 spectrum, characteristic for the P emission of 8740. 0 E-mail address: r.piramidowicz@imio.pw.edu.pl (R. Piramidowicz) praseodymium has been observed between 10 and 300 K 0925-8388 / 00 / $ – see front matter  2000 Elsevier Science S.A. All rights reserved. PII: S0925-8388(99)00757-4