Optical properties of Nd 3+ doped bismuth zinc borate glasses B. Shanmugavelu a , V. Venkatramu b , V.V. Ravi Kanth Kumar a,⇑ a Department of Physics, Pondicherry University, Puducherry 605 014, India b Department of Physics, Yogi Vemana University, Kadapa 516 003, India highlights  Luminescence quenching occurs at high concentration of Nd 3+ ion.  The interaction between Nd 3+ ions is of dipole–dipole type.  The experimental branching ratio of 4 F 3/2 to 4 I 11/2 transition is high. graphical abstract Emission spectra of the BZB glasses with various Nd 3+ ion concentrations. article info Article history: Received 7 August 2013 Received in revised form 21 October 2013 Accepted 10 November 2013 Available online 21 November 2013 Keywords: Borate glasses Judd–Ofelt analysis Luminescence Radiative properties Lifetime abstract Glasses with compositions of (100x) (Bi 2 ZnOB 2 O 6 )  x Nd 2 O 3 (where x = 0.1, 0.3, 0.5, 1 and 2 mol%) were prepared by melt quenching method and characterized through optical absorption, emission and decay curve measurements. Optical absorption spectra have been analyzed using Judd–Ofelt theory. The emission spectra exhibit three peaks at 919, 1063 and 1337 nm corresponding to 4 F 3/2 to 4 I 9/2 , 4 I 11/2 and 4 I 13/2 transitions in the near infrared region. The emission intensity of the 4 F 3/2 to 4 I 11/2 transi- tion increases with increase of Nd 3+ concentration up to 1 mol% and then concentration quenching is observed for 2 mol% of Nd 3+ concentration. The lifetimes for the 4 F 3/2 level are found to decrease with increase in Nd 2 O 3 concentration in the glasses. The decay curves of the glass up to 0.3 mol% of Nd 3+ exhibit single exponential nature and thereafter the curves become nonexponential nature (0.5, 1 and 2 mol%). The nonexponential curve has been fitted to the Inokuti–Hirayama model to understand the nature of energy transfer process. Ó 2013 Elsevier B.V. All rights reserved. Introduction Nd 3+ doped glasses have been extensively investigated for their commercially important laser radiation at around 1064 nm in the near infrared region [1–5]. In addition, Nd 3+ doped glasses are studied for their 1.3 lm luminescence that can be utilized for optical amplification in the near infra red region [6,7]. These glasses are also explored for their infrared to visible up-conversion luminescence [8,9]. Nd 3+ doped glasses are used as an effective gain medium in the high power solid state lasers, which can be used in laser inertial nuclear fusion energy power plants to gener- ate electricity [10]. Owing to the commercial importance of Nd 3+ doped glass lasers, many studies on optical properties of Nd 3+ ions in the different glass matrices have been carried out [11–13]. The fluorescence efficiency of the Nd 3+ doped glasses mainly depend on the constituents present in the glasses. The presence of heavy metal oxides such as PbO and Bi 2 O 3 in glasses leads to the efficient radiative transitions in rare earth doped systems due to their higher refractive index [14–20]. 1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2013.11.051 ⇑ Corresponding author. Tel.: +91 413 2654406; fax: +91 413 2655368. E-mail address: ravi.phy@pondiuni.edu.in (V.V. Ravi Kanth Kumar). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 122 (2014) 422–427 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa