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

• Er3+ and Nd3+ singly and codoped fluoroaluminate glasses with low phosphate content are successfully prepared.
• The Judd–Ofelt (J–O) and radiative parameters are calculated and discussed.
• 0.9, 1.05 μm emissions from Nd3+ and 1.5, 2.7 μm emissions from Er3+ are discussed in the singly and codoped samples.
• The energy transfer efficiencies of the Nd3+: 4F3/2 to the Er3+: 4I11/2 and the Er3+: 4I13/2 to the Nd3+: 4I15/2 are 28.8% and 74.5%, respectively.

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 μm decrease in the codoped sample under the excitation of an 800 nm laser diode from the emission spectra because the Er3+: 4I11/2 level reduces the Nd3+: 4F3/2 level effectively through the energy transfer process Nd3+: 4F3/2 → Er3+: 4I11/2. For Er3+, the emission at 1.5 μm is restrained by codoping with Nd3+ ions from the energy transfer process Er3+: 4I13/2 → Nd3+: 4I15/2. The emission at 2.7 μm 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+: 4F3/2 to the Er3+: 4I11/2 and the Er3+: 4I13/2 to the Nd3+: 4I15/2 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 μm laser generation.