Influence of multiphonon and cross relaxations on P-3(0) and D-1(2) emission levels of Pr3+ doped borosilicate glasses for broad band signal amplification

Abstract

We discuss non-radiative relaxations of visible-near infrared (Vis-NIR) emissions originating from P-3(0) and D-1(2) levels of Pr3+ glasses. Thermal stability of host lithium aluminium borosilicate (LABS) glass is estimated from thermogravimetric and differential thermal analysis. The structural analysis of host LABS glass through Fourier transform infrared and Raman spectral profiles provide an insight to understand the effect of OH content and phonon energy on luminescence characteristics of Pr3+ ions. Visible emission spectrum of Pr3+ glass is composed of two prominent emission bands at 493 nm (P-3(0) -> H-3(4)) and 605 nm (D-1(2) -> H-3(4)) when excited by 448 nm. In NIR region a narrow emission band at 1.06 mu m (D-1(2) -> 3F3) and ultra-broad emission band at 1.49 mu m (D-1(2) -> (1)G(4)) are observed for 488 nm excitation. For these emission transitions, emission decay curves are measured and analysed. The lifetime shortening due to non-radiative energy transfer is explained by multiphonon interactions and cross-relaxation routes, and later verified by Dexter's model. Electric dipole-dipole mechanism is identified to be responsible for ion-ion interactions intervening in P-3(0) and D-1(2) states of Pr3+ causing quenching in emission intensities and lifetimes. The large absorption and stimulated emission cross-sections of Pr3+ ions around 1.49 mu m suggests suitability of a host material operating for broadband signal amplifications at low-loss optical telecommunication windows. Besides, emission parameters like stimulated emission cross-section (sigma(emi)), effective band width (Delta lambda(eff)) are calculated for 1.49 mu m (D-1(2) -> (1)G(4)) of Pr3+ doped silicate based glasses. (C) 2016 Elsevier B.V. All rights reserved.