Influence of borate content on the radiative properties of Nd 3þ ions in fluorophosphate glasses G.A. Kumar a, * , E. De la Rosa-Cruz b , A. Martinez b , N.V. Unnikrishnan c , K. Ueda a a Institute for Laser Science, University of Electro Communication, Tokyo 182 8585, Japan b Centro de Investigaciones en Optica A.C., A.P. 1-948, Leon Gto. 37160, Mexico c School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam 686 560, India Received 11 April 2001; accepted 20 March 2002 Abstract Spectroscopic properties of Nd 3þ in barium fluoroborophosphate glassy matrix have been analyzed by fitting the experimental data with the standard Judd–Ofelt theory. Various spectroscopic parameters viz. radiative transition probabilities, radiative decay time, fluorescence branching ratios, electric dipole line strengths, stimulated emission cross-sections and optical gain of the principal fluorescence transitions from the 4 F 3/2 metastable level are obtained. Results show that addition of borate content to the fluorophosphate matrix will reduce the fluorescence spectral properties of Nd 3þ . However, the radiative properties of the present fluoroborophosphate glassy matrix are found to be well improved over that of pure borate and phosphate matrix and is attributed to the influence of fluorine content in the glassy matrix. The changes in the position and the Judd–Ofelt intensity parameters are correlated with the structural changes in the host glass matrix. The shift of the hypersensitive band shows that the covalency of the rare earth to oxygen bond increases with the increase of Na 2 O content. This covalency effect and the formation of the BO 4 groups with the addition of Na 2 O content are responsible for the increase in the radiative properties of the present system. Quantitative estimation of the non-radiative processes such as multiphonon relaxation and quenching by water content was carried out and the results show that both are below the critical level for optimum laser performance. q 2002 Elsevier Science Ltd. All rights reserved. Keywords: A. Chalcogenides; A. Elements; A. Glasses 1. Introduction Over the past several decades, considerable work have been carried out on the spectroscopic and laser character- istics of trivalent neodymium ions (Nd 3þ ) in different host, both crystalline and amorphous [1–6]. The suitability of this ion in producing strong infrared fluorescence radiations makes it as a possible candidate in high power laser applications. It is well known that the stimulated emission characteristic of a trivalent rare earth ion depends considerably on the surrounding host matrix in which they are incorporated. The surrounding ligand field can have a considerable influence on the optical absorption cross- section, stimulated emission cross-section and fluorescence decay, and hence the quantum efficiency of the system. It was found that these three parameters are the key factors controlling the stimulated emission properties of a trivalent rare earth ion in any host matrix. When considering the active applications such as laser amplifiers, one of the important requirements for high quantum yield is that the non-radiative processes by multiphonon relaxation should be minimized. The vibra- tional frequencies of fluoride group is found to be lower and hence rare earth doped fluoride glasses are of particular interest to laser researchers especially in the field of fiber amplifiers. A lot of work has been done over the past several decades on the spectroscopic properties of Nd 3þ ion in a variety of glassy matrix including phosphate [7], borate [8], sulphate [9], fluorides [10], telluride [11] and chalcogenides [12]. The fluorescence properties of Nd 3þ can be tailored over a considerable extent by suitably selecting the network 0022-3697/03/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved. PII: S0022-3697(02)00213-5 Journal of Physics and Chemistry of Solids 64 (2003) 69–76 www.elsevier.com/locate/jpcs * Corresponding author. E-mail address: akgsh@yahoo.com (G.A. Kumar).