Red, green, and blue upconversion luminescence in ytterbium-sensitized praseodymium-doped lead–cadmium–germanate glass A.S. Gouveia-Neto a, * , E.B. da Costa a , L.A. Bueno b , S.J.L. Ribeiro b a Departamento de F  ısica e Matem atica, Laborat orio de Fot^ onica, Universidade Federal Rural de Pernambuco, Recife 52171/900, PE, Brazil b Instituto de Qu  ımica, UNESP, Araraquara 14800/900, SP, Brazil Received 22 September 2003; received in revised form 10 December 2003; accepted 23 December 2003 Available online 12 March 2004 Abstract Blue, green, red, and near-infrared upconversion luminescence in the wavelength region of 480–740 nm in Pr 3þ /Yb 3þ -codoped lead–cadmium–germanate glass under 980 nm diode laser excitation, is presented. Upconversion emission peaks around 485, 530, 610,645,and725nmwhichwereascribedtothe 3 P 0 – 3 H J (J ¼ 4,5,and6),and 3 P 0 – 3 F J (J ¼ 2, 3, and 4), transitions, respectively, were observed. The population of the praseodymium upper 3 P 0 emitting level was accomplished through a combination of ground- state absorption of Yb 3þ ions at the 2 F 7=2 , energy-transfer Yb 3þ ( 2 F 5=2 )–Pr 3þ ( 3 H 4 ), and excited-state absorption of Pr 3þ ions pro- voking the 1 G 4 – 3 P 0 transition. The dependence of the upconversion luminescence upon the Yb 3þ -concentration and diode laser power, is also examined, in order to subsidize the proposed upconversion excitation mechanism. Ó 2004 Elsevier B.V. All rights reserved. Keywords: Luminescence; Rare-earth; Glass; Thermal-effect; Upconversion 1. Introduction Overthepastfewdecades,therehasbeenasignificant interest in the production of new vitreous materials which find application as hosts in rare-earth doped infrared-to-visible light upconverters. Some of their many applications include color displays, high density optical data reading/storage, biomedical diagnostics, infraredlaserviewersandindicators,etc.Topursuethat purpose, it is important to study frequency upconver- sion processes [1] in alternative materials and identify the major relaxation and interaction mechanisms of rare-earths doping in the new matrix. Among the novel materials available, PbGeO 3 –PbF 2 –CdF 2 glasses [2,3], emerge as serious contenders for photonic devices applications. These glasses are advantageous because they present better mechanical strength, chemical durability, and thermal stability than fluoride-based glasses and are suitable for developing low-loss, high strength, and low-cost optical fibers. In addition, the glass host matrices possess the durability and mechani- cal properties of an oxide glass and the maximum vibrational energy is intermediate (800 cm 1 ) between those of silicate (1100 cm 1 )andfluoride(500cm 1 ) based glasses. For the majority of rare-earth single-doped systems the upconversion process has proven inefficient for pumping in the wavelength region around 1.0 lm, par- ticularly for those ions capable of generating blue up- conversion emission. However, when rare-earth doped materials are sensitized by trivalent ytterbium [4–9], the high absorption cross-section of the ytterbium sensitizer and the efficient energy-transfer mechanism between Yb 3þ ions and the rare-earth acceptor ions, yield a considerableenhancementintheupconversionefficiency as demonstrated for Tm 3þ /Yb 3þ -[4],Pr 3þ /Yb 3þ - [5–12], and recently in Er 3þ /Yb 3þ -codoped glasses [13]. In the reports of Ref. [13], an enhancement by a factor of ·20 * Corresponding author. Tel.: +55-81-33021480; fax: +55-81- 33021011. E-mail address: artur@ufrpe.br (A.S. Gouveia-Neto). 0925-3467/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.optmat.2003.12.012 Optical Materials 26 (2004) 271–274 www.elsevier.com/locate/optmat