Abstract

Er³⁺-doped glass and fiber are very attractive for near-infrared (NIR) lasers and photonic applications. In this work, the full width at half maximum (FWHM) of NIR fluorescence emission of the Er³⁺-doped germanate glass can be broadened from 72 to 99 nm when Al₂O₃ was added. In addition, the spectroscopic properties, including absorption and emission spectra, Judd–Ofelt intensity parameters, absorption and emission cross sections, gain coefficient, and fluorescence lifetime, of the Al₂O₃-modified germanate glass were systematically investigated. What is more, silicate-clad heavily Er³⁺-doped germanate core multimaterial fibers were successfully drawn by a rod-in-tube method. Notably, broadband NIR amplified spontaneous emission (ASE) with an FWHM of 120 nm was achieved in this new fiber. To the best of our knowledge, this is the largest FWHM reported for Er³⁺-doped germanate glass fibers. These results suggest that the as-drawn Er³⁺-doped germanate glass fiber with superior performances is a promising candidate for broadband optical amplification.

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