Fluorescence quantum efficiency dependent on the concentration of Nd 3+ doped phosphate glass A.A. Andrade a,⇑ , V. Pilla a , S.A. Lourenço b , A.C.A. Silva c , N.O. Dantas c a Grupo de Propriedades Ópticas e Térmicas de Materiais (GPOTM), Instituto de Física, Universidade Federal de Uberlândia, CP 593, 38400-902 Uberlândia, MG, Brazil b Universidade Tecnológica Federal do Paraná, Campus Londrina, 86036-370 Londrina, PR, Brazil c Laboratório de Novos Materiais Isolantes e Semicondutores (LNMIS), Instituto de Física, Universidade Federal de Uberlândia, CP 593, 38400-902 Uberlândia, MG, Brazil a r t i c l e i n f o Article history: Received 19 March 2012 In final form 26 July 2012 Available online 14 Augus t 2012 a b s t r a c t The thermal-lens (TL) method was applied to a new phosphate glass doped with Nd 3+ to determine fluo- resc ence quan tum effic iency (g) and therm al prop ertie s such as: ther mal diff usivi ty, therm al cond uctiv ity and the temperature coefficient of optical length change. Studies were performed as a function of Nd 3+ concentration (0.5–3 10 20 ions/cm 3 ). In add ition , fluor esce nce quen ching was studi ed by mea surin g the concentration dependence of fluorescence lifetime. The TL and fluorescence lifetime results are in good agreement and corroborate the theory for energy transfer involving a pair of ions in which cross- relaxation (CR) is the dominant process. 2012 Elsevier B.V. All rights reserved. 1. Introduction Phosphate glasses containing rare earth ions belong to a broad family of heavy metal glasses that are among the most promising glass y mat rices for seve ral app lica tion s. For exa mpl e, they are attractive in optical applications because they belong to a limited number of host matrices that can accommodate higher concentra- tions of ions (e.g. Nd 3+ ) and remain amorphous relative to other oxide glasses. Fluorescence quantum efficiency ( g) is an important parameter for laser applications and is defined as the ratio of the number ofradiative deexcitations to the total number of deexcitations of an energy state in a given system[1]. It is well known that efficient solid state lasers require an active medium that is usually com- prise d of ion do ped gla sse s or crystals with hig h rad iat ion emiss io n rat es. This me ans tha t bo th abs or bed lig ht and gmus t beas hi gh as possible. For other applications such as optical amplifiers, g also needs to be near unit. Therefore, the absolute determination ofg for luminescent materials is indispensable. For example, a Nd 3+ -doped phosphate matrix has fluorescence quantum efficiency that is higher than that of aluminates[2] and sim ila r to tha t of fluo rid es [3,4]. These char acte rist ics and exce llen t ther mal and mechanical pro per ties ma ke them desirable cand i- dates for laser applications. Thus, the aim of this study was to determine the optical and ther mal prope rties of a new phosph ate glas s matrix, PANK. The thermal properties of this matrix were quantified by the thermal lens (TL) techniqu e. To the best of the authors’ knowle dge the PANK was probably first proposed as a host for Nd 3+ due to its transparency from UV to the near infrared. This range of the elec- tromagnetic spectrum is where, according to the Judd–Ofelt the- ory, absorption , emission and all other electronic transitions occur. The Nd 3+ ion was chosen because of impo rta nt features tha t dis- tingu ish it from othe r opt icall y activ e ions. Firs t among these is that its emission and absorption transition wavelengths are rela- tively host insensitive. In addition, the lifetime of its metastable state ( 4 F 3/2 ) is long [5] (e.g. 300–1200 ls in Nd 3+ -doped silicate glasses) and its fluorescent quantum efficiencyg tends to be high (e.g. g= 0. 95 fo r Nd 3+ -do ped GaLaS, ZBL AN and PGIZ Ca glas ses [6]and Nd 3+ :YAG crystal [7]). Because of this and other qualities, Nd 3+ has been extensively studied as a dopant in different materi- als such as silicate [8], phosphate [9] , fluorophosphates [10] and fluoride glasses[4,11,12]. Our TL experiments were performed with seven concentrations of Nd 3+ . The optical absorption coefficient and luminescence spec- tra were also measured. 2. Experimental details Glas ses wer e synth esiz ed by fusio n of neo dymium dioxid e xNd 2 O 3 (wt.%), ( x= 1, 2, 3, 4, 5, 6 and 7). The nom inal com posi tion of this new phosphate glass matrix (PANK) was 40P 2 O 5 20Al 2 O 3- 35Na 2 O5K 2 O (mo l%). Powder was melted in por celain cruc ible s and a carbon rich atmosphere at 1350 C for 30 min . Afte rwa rds , the melt was rapidly cooled between graphite plates in an oven at 250 C. The result ing bla de s were heated at 35 0 C for 48 h tore - move internal stresses. 0009-2614/$ - see front matter2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cplett.2012.07.062 ⇑ Corresponding author. E-mail address: andrade@infis.ufu.br(A.A. Andrade). Chemical Physics Letters 547 (2012) 38–41 Contents lists available at SciVerse ScienceDirect Chemical Physics Letters journal homepage: www.elsevier.com/locate/cplett
