Self-quenching of spontaneous emission in Sm 3+ doped lead-borate glass G. Manoj Kumar, B.N. Shivakiran Bhaktha, D. Narayana Rao * School of Physics, University of Hyderabad, Hyderabad 500 046, India Received 15 July 2005; received in revised form 13 January 2006; accepted 16 January 2006 Available online 11 April 2006 Abstract The lifetimes of Sm 3+ doped in a binary glass are studied as a function of the complex refractive index of the glass. The local field effect has been taken into account and a real cavity around the emitter is assumed. The results are analyzed in the framework of the quantum electrodynamical equation to obtain a parameter that is related to the radius of cavity around Sm 3+ . The knowledge of this parameter is crucial in tailoring the lifetimes and has been found to be 1.48 nm. Ó 2006 Elsevier B.V. All rights reserved. PACS: 42.65.Pc; 32.70.Cs; 42.70.Ce Keywords: Local field effects; Lifetimes; Glasses 1. Introduction In the light of rapid growth of photonics based applica- tions, such as lasers, phosphors, display monitors, upcon- version and amplifiers for fiber optic communications [1–3], the study of the rare earth doped materials has once again secured the attention of researchers world over. The spectral properties vis-a `-vis fluorescence widths and the lifetimes, play a crucial role in the choice of materials for device fabrication. In this context, spectral hole burning investigations have been conducted on samarium [4] to explore high-density optical memory. Also, it has been observed that co-doping of samarium and europium in zinc sodium phosphate glass leads to energy transfer that affects the emission of Eu 3+ [5]. The tailoring of lifetimes of Sm 3+ as a function of its concentration in a binary glass system has been presented here. Einstein [6] established that an excited species must undergo spontaneous emission (SE) in order to achieve thermal equilibrium between the matter and radiation. This picture is so fundamental, that it is often believed that the SE lifetime is an immutable property of the atom. The modification of the SE lifetimes of rare earths is a tempting goal with scope for a variety of potential applications. The fact that the SE rates can be altered is embodied in the Fer- mi’s golden rule – the lifetime depends on the electronic wavefunctions of the states involved as well as the elec- tro-magnetic field strength and the density of modes at the position of the atom. Purcell [7] was the first to observe that any change in the environment can alter the SE rates. Drexhage [8,9] has performed some of the pioneering experiments on the subject of modification of SE. Many other experiments [10–14] have been performed showing the inhibition and enhancement of the SE attributing the effect to the change in mode density at the position of the emitter. However, it is far easier to change the electromag- netic field strength that can be achieved by changing the refractive index of the dielectric. 2. Local field effect The subject of the SE in a dielectric has been studied both theoretically and experimentally. The applied field 0925-3467/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.optmat.2006.01.020 * Corresponding author. Tel.: +91 40 23011230; fax: +91 40 23010227. E-mail address: dnrsp@uohyd.ernet.in (D. Narayana Rao). www.elsevier.com/locate/optmat Optical Materials 28 (2006) 1266–1270