Judd-Ofelt analysis and energy transfer processes of Er3+ and Nd3+ doped fluoroaluminate glasses with low phosphate content

Spectroscopic property and energy transfer processes of singly doped and codoped Er3+ and Nd3+ fluoroaluminate glasses with low phosphate content are systematically analyzed. The absorption spectra of these glasses are tested, and the Judd-Ofelt (J-O) and radiative parameters are discussed based on J-O theory and the parameters changes substantially because of the other codoping ions. As for Nd3+: the main emission bands at 0.9 and 1.05 mu m decrease in the codoped sample under the excitation of an 800 nm laser diode from the emission spectra because the Er3+: I-4(11/2) level reduces the Nd3+: I-4(3/2) level effectively through the energy transfer process Nd3+: F-4(3/2) -> Er3+: I-4(11/2). For Er3+, the emission at 1.5 mu m is restrained by codoping with Nd3+ ions from the energy transfer process Er3+: I-4(13/2) -> Nd3+: I-4(15/2). The emission at 2.7 mu m is enhanced because the Nd3+ ions deplete the lower level and exert a positive effect on the upper laser level. The microparameters of the energy transfer between the Er3+ and Nd3+ ions are calculated and discussed using Forster-Dexter theory. The energy transfer efficiencies of the Nd3+: F-4(3/2) to the Er3+: I-4(11/2) and the Er3+: I-4(13/2) to the Nd3+: I-4(15/2) are 28.8% and 74.5%, respectively. These results indicate that Nd3+ can be an efficient sensitizer for Er3+ to obtain Mid-infrared (Mid-IR),emission and the codoped Er3+/Nd3+ fluoroaluminate glass with low phosphate content is suitable to be used as the fiber optical gain media for 2.7 mu m laser generation. (C) 2014 Elsevier B.V. All rights reserved.