Contents lists available at ScienceDirect Optical Materials journal homepage: www.elsevier.com/locate/optmat Optical and luminescence characteristics of Sm 3+ doped B 2 O 3 -GeO 2 -Gd 2 O 3 glasses Melis Gökçe * , Deniz Koçyiğit Department of Physics, Adnan Menderes University, Aydın, 09010, Turkey ARTICLE INFO Keywords: Glass Luminescence Judd-Ofelt analysis Radiative properties Decay time ABSTRACT Glasses with the composition of 30B 2 O 3 e40GeO 2 -(30-x)Gd 2 O 3 -xSm 2 O 3 (x = 0.25, 0.5, 1 and 1.5 mol%) have been prepared by melt quenching technique. Their optical and luminescence properties were analyzed via ab- sorption, photoluminescence and decay time measurements. Judd–Ofelt intensity parameters (Ω λ , λ = 2,4,6) obtained from the absorption spectrum follow the trend Ω 4 > Ω 2 > Ω 6 . Photoluminescence spectra revealed a dominant emission band at 597 nm which was attributed to 4 G 5/2 → 6 H 7/2 transition. From the emission spectra and Judd–Ofelt intensity parameters radiative properties including transition probabilities (A), radiative decay times (τ R ), branching ratio (β R ) and stimulated emission cross-section (σ p E ) were calculated. The decay curves of 4 G 5/2 level exhibited non-exponential behavior and well fitted to Inokuti-Hirayama model for S = 6. The ana- lyzed spectroscopic properties viz. A, β R , σ p E and CIE chromaticity coordinates demonstrate the suitability of BGGS1.00 glass for visible reddish-orange laser applications among the prepared glasses. 1. Introduction Due to their high luminescence efficiencies, rare earth (RE) ion doped glasses are very attractive materials which are alternatives to single crystal and ceramic materials for scintillator and optical appli- cations in high-energy physics, industry, medical imaging and lasers [1,2]. This luminescence corresponds to 4f–4f and 4f-5d electronic transitions in the RE ions. The local symmetry, ligand field and the phonon energy of the host material affect the transitions originated from 4f electronic states. Therefore it is very important to evaluate the spectroscopic properties of the RE ion in the particular host for research and development of optoelectronic devices. Judd-Ofelt (JO) [3,4] theory is used to calculate these spectroscopic properties such as ra- diative transition probabilities, radiative decay times, branching ratios and stimulated emission cross-sections. Oxide glasses such as silicate, phosphate, tellurite and borate are stable hosts for obtaining efficient luminescence with RE ions and are used in many photonic applications and industrial areas [5–8]. The large mass of germanium provides smaller vibrational frequencies to germanate glasses than counterparts such as borate, silicate and phos- phate glasses. The quantum efficiency of luminescence which is an es- sential property for laser medium will be improved by the reduced phonon energy of these materials [9]. Among phosphate, silicate or borosilicate glass systems, borogermanate glasses have come into pro- minence due to their high doping capacity for RE ions, high thermal stability, high transparency, lower melting point, lower phonon energy and moisture resistance [10,11]. Gd 3+ RE ion may act as a network modifier in oxide glasses. The incorporation of Gd 2 O 3 into the glass matrix provides remarkable benefits such as efficient energy transfer from Gd 3+ ions to the luminescence centers, an increment in the light yield of emission, increase in glass density and relatively low cost [12–14]. The spectroscopic and optical properties of gadolinium bor- ogermanate glasses doped with various RE ions such as Ce [15] and Tb [16] have been investigated so far. Recently, our group reported the effect of Eu 3+ concentration on the luminescence properties of gado- linium borogermanate glasses [14]. Among RE ions, trivalent samarium (Sm 3+ ) presents high solubility in germanate glasses has been emerged as one of the most promising RE oxide owing to its potential application in solid state lightening, color displays, high-density optical storage, temperature sensors and un- dersea communication [17,18]. Sm 3+ ions exhibit excellent reddish- orange luminescence corresponding to 4 G 5/2 → 6 H 5/2 , 6 H 7/2 , 6 H 9/2 and 6 H 11/2 transitions [19]. The intensities of these bands are affected by glass matrix and the concentration of Sm 3+ ion [20]. Many researchers investigated the structural, optical and luminescence properties of Sm 3+ ions in different hosts such as silicate [6,10,21], borate [7,20,22,23], phosphate [5,16,18,24], tellurite [8,25] and lanthanum borogermanate [9]. The objective of the present study is to develop and characterize Sm 3+ ion doped gadolinium borogermanate glasses and to optimize the https://doi.org/10.1016/j.optmat.2018.06.015 Received 10 May 2018; Received in revised form 1 June 2018; Accepted 10 June 2018 * Corresponding author. E-mail address: mgokce@adu.edu.tr (M. Gökçe). Optical Materials 83 (2018) 233–240 0925-3467/ © 2018 Elsevier B.V. All rights reserved. T