Nd3+:Ga-Ge-Sb-S glasses and fibers for luminescence in mid-IR: synthesis, structural characterization and rare earth spectroscopy

With high refractive indices, appropriate solubility of rare earth, low phonon energy and transparency from the visible to 10 mu m, a Ga-Ge-Sb-S system allows emission from Nd3+ ions in the near-and mid-IR spectral ranges. The glass transition temperature, density, expansion coefficient, and near and mid-IR refractive indexes were measured on bulk samples. Their glass network structures were analyzed by Raman scattering spectrometry, NMR of Ga-71 and extended X-ray absorption fine structure (EXAFS, K-edge of Ga, Ge, Sb, S and Nd). The absorption and emission spectra of neodymium doped sulfide glasses were recorded from the visible to the mid-IR. Excited state lifetimes were measured for several transitions. The lifetimes decrease with the concentration of Nd3+, especially for the I-4(13/2) and I-4(11/2) levels. The spectroscopic parameters were determined by the Judd-Ofelt method, allowing the calculation of cross-section emissions and the evaluation of quantum yields. Optical attenuation and emission measurements of fiber were also performed with a broad 4.7-5.7 mu m emission band in the mid-IR.