Judd-Ofelt analysis and energy transfer processes of Er~(3+) and Nd~(3+) doped fluoroaluminate glasses with low phosphate content

摘要

Spectroscopic property and energy transfer processes of singly doped and codoped Er~(3+) and Nd~(3+) 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-0 theory and the parameters changes substantially because of the other codoping ions. As for Nd~(3+): 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 Er~(3+): ~4I_(11/2) level reduces the Nd~(3+): ~4F_(3/2) level effectively through the energy transfer process Nd~(3+): ~4F_(3/2) → Er~(3+): ~4I_(11/2). For Er~(3+), the emission at 1.5 μm is restrained by codoping with Nd~(3+) ions from the energy transfer process Er~(3+): ~4I_(13/2) → Nd~(3+): ~4I_(15/2). The emission at 2.7 μm is enhanced because the Nd~(3+) ions deplete the lower level and exert a positive effect on the upper laser level. The microparameters of the energy transfer between the Er~(3+) and Nd~(3+) ions are calculated and discus.sed using Forster-Dexter theory. The energy transfer efficiencies of the Nd~(3+): ~4F_(3/2) to the Er~(3+): ~4I_(11/2) and the Er~(3+): ~4I_(13/2) to the Nd~(3+): ~4I_(15/2) are 28.8% and 74.5%, respectively. These results indicate that Nd~(3+) can be an efficient sensitizer for Er~(3+) to obtain Mid-infrared (Mid-IR) emission and the codoped Er~(3+)/Nd~(3+) fluoroaluminate glass with low phosphate content is suitable to be used as the fiber optical gain media for 2.7 μm laser generation.