Author's personal copy Photoluminescence properties of Sm 3+ in LBTAF glasses B.C. Jamalaiah, J. Suresh Kumar, A. Mohan Babu, T. Suhasini, L. Rama Moorthy à Department of Physics, Sri Venkateswara University, Tirupati 517 502, India article info Article history: Received 5 May 2008 Received in revised form 25 October 2008 Accepted 4 November 2008 Available online 19 November 2008 PACS: 71.20.Eh 71.23.Cq 71.55.Jv 78.55.Qr Keywords: Glasses Rare earths J–O theory Optical properties Fluorescence Lifetimes abstract Room temperature visible and near infrared optical absorption and emission spectra of Sm 3+ -doped lead borate titanate aluminum fluoride (LBTAF) glasses with molar composition (50x) PbO30H 3- BO 3 10TiO 2 10AlF 3 xSm 2 O 3 (x ¼ 0.1, 0.5, 1.0 and 2.0) have been analyzed. Energy parameters for the 4f 5 electronic configuration of Sm 3+ : LBTAF glasses have been evaluated using free-ion Hamiltonian model. The experimental oscillator strengths of absorption bands have been used to determine the J–O parameters. Fluorescence spectra were recorded by exciting the samples with 402 nm. Using the J–O parameters and luminescence data, the radiative transition probabilities (A R ), branching ratios (b R ) and stimulated emission cross-sections (s e ) were obtained. The decay curves of 4 G 5/2 - 6 H 7/2 transition exhibit single exponential for lower concentration (0.1 mol%) and non-exponential for higher concentrations. This concentration quenching has been attributed to the energy transfer through cross-relaxation between Sm 3+ ions. From the values of the radiative parameters, it is concluded that 1.0 mol% Sm 3+ -doped LBTAF glass may be used for laser active medium with emission wavelength at 600 nm. & 2008 Elsevier B.V. All rights reserved. 1. Introduction Interesting spectroscopic properties of the trivalent lanthanide ions led to the development of the lanthanide-doped glasses as laser materials. Efficient laser hosts can be realized using heavy metal oxide glasses in view of their low phonon energy [1]. Host glasses with low phonon energies allow large radiative transition rates that are useful for the design and development of optical devices. Borate glasses, incorporated by heavy metal oxides, can give intense fluorescence in the visible spectral region which is used as electro-optic modulators, electro-optic switches, solid state laser materials and non-linear parametric converters [2–5]. Investigations on the optical absorption and fluorescence studies of rare-earth ion-doped glasses found wide applications in the fields of lasers and telecommunications. In this direction a great amount of research has been carried out to develop new glass matrices containing rare-earth (RE) ions. Sm 3+ ion with 4f 5 electronic configuration exhibit a strong orange-red fluorescence in the visible region. The very large number of energy levels lying close to each other renders the interpretation of the absorption spectra rather cumbersome. Mahato et al. [6] reported the concentration quenching of fluorescence of 4 G 5/2 level and attributed it to quadrupole–qua- drupole interaction among the Sm 3+ ions. In the present work, we have studied the absorption, fluorescence and decay processes of Sm 3+ ions with different concentrations in LBTAF glasses. The phenomenon of concentration quenching and the involved mechanism have been discussed. 2. Experimental method The chemical composition of different concentrations of Sm 3+ - doped LBTAF: (50x) PbO+30H 3 BO 3 +10TiO 2 +10AlF 3 +xSm 2 O 3 , where x ¼ 0.1, 0.5, 1.0 and 2.0mol% glasses were prepared. The starting reagents for the glass preparation were powdered and melted in an electric furnace at 1050 1C in porcelain crucible for about 1 h. The melt was poured onto pre-heated brass moulds. In order to remove thermal strain, the glass samples were annealed for 8 h at 360 1C and then cooled to room temperature. The glasses exhibit the typical yellow color of the Sm 3+ ion [7]. The density (5.45 g/cm 3 ) of the glass sample was determined by Archimede’s method, using xylene as the immersion liquid and the refractive index of 1.594 was measured using Abbe’s refractometer (Model: GE-138) at sodium wavelength with ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jlumin Journal of Luminescence 0022-2313/$ - see front matter & 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jlumin.2008.11.001 à Corresponding author. Tel.: +91877 2249666x272 (O), +91877 2242766; fax: 918777 222521. E-mail address: lrmphysics@yahoo.co.in (L. Rama Moorthy). Journal of Luminescence 129 (2009) 363–369