In this paper, a 2 µm broadband emission under 796 nm laser diode excitation in low phonon energy GeO₂-Ga₂O₃-BaO glass system is co-doped with 0.7Tm₂O₃/(0.07-0.7)Ho₂O₃ (mol%). The widest emission band (where the Tm³⁺ → Ho³⁺ energy transfer efficiency is 63%) was obtained for 0.7Tm₂O₃/0.15Ho₂O₃ co-doped glass from which a double-clad optical fiber was realized and investigated. Optimization of Tm³⁺/Ho³⁺ concentration enabled the acquisition of broadband amplified spontaneous emission (ASE) in double-clad optical fiber with a full width at half maximum (FWHM): 377 nm and 662 nm for 3 dB and 10 dB bandwidth, respectively. ASE spectrum is a result of the superposition of (Tm³⁺: ³H₄ →Η³F₄) 1.45 µm, (Tm³⁺: ³F₄ → ³H₆) 1.8 µm and (Ho³⁺:⁵I₇ → ⁵I₈) 2 µm emission bands. Hence, highly rare-earth co-doped germanate glass is characterized by a remarkably broader ASE spectrum than silica and tellurite fibers showed promising lasing properties for their further application in tunable and dual wavelength lasers.

Thermal stability and broadband NIR luminescence of Pr³⁺ doped gallo-germanate glasses with BaF₂ have been studied. The thermal factors are larger for glass samples with low BaF₂ content exhibiting good thermal stability against devitrification. Luminescence due to ¹D₂ → ¹G₄ transition of Pr³⁺ was measured under 450 nm excitation. The ¹D₂ measured lifetimes depend critically on activator concentration, but remain nearly unchanged with BaF₂ content. The emission linewidth, the emission cross-section, the figure of merit (FOM) and the σ_em x FWHM product are relatively large, suggesting that Pr³⁺-doped gallo-germanate glasses with presence of BaF₂ are promising as gain media for broadband near-infrared amplifiers.