A detailed investigation of concentration quenching and ion clustering effects in Er:YAG-derived all-glass optical fibers fabricated using the molten core method (MCM) is presented. Fibers are drawn from four precursor Er:YAG crystals, each possessing a different Er3+ concentration. The resulting fibers exhibited active ion densities ranging from 2.58 × 1025 m-3 to 19.5 × 1025 m-3. Compositional and refractive index profiles (RIPs) are shown to be uniformly graded across the fibers, for a given core diameter, facilitating the study of the impact of draw and host composition on rare earth spectroscopy, a first to the best of the Author’s knowledge. Measurements of the fluorescence lifetimes indicate some degree of clustering persists in all fibers; however, its reduction can clearly be correlated to an increase in sesquioxide (Al2O3 and Y2O3) concentration. Similarly, the critical quenching concentration is also revealed to increase with increasing sesquioxide concentration and ranged from 23.9 × 1025 m-3 to 40.4 × 1025 m-3 in the present fibers. Finally, emission and absorption spectra were found to be practically indistinguishable between the various fibers, with a zero-concentration radiative lifetime determined to be around 8.3 ms. Compared with other silica-based hosts, this lifetime is slightly lower, giving rise to proportionately higher cross-sections.

A barium fluorosilicate glass fiber, when pumped in the infrared, exhibits powerful green surface-like defect luminescence whose intensity is a strong function of temperature. Optical thermometry over the range from 25°C-130°C is demonstrated.

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A barium fluorosilicate glass fiber, when pumped in the infrared, exhibits powerful green luminescence whose intensity maintains a Pekarian-lineshape. Combined with correlated Raman spectroscopy, oxygen-excess surface defects are suggested as the origin.

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