Broadband NIR emission in glasses and multicore optical fibers co-doped with Ni²⁺/Cr³⁺/Bi³⁺ and rare-earth ions (Invited Paper)

In the paper, the possibility of obtaining broadband NIR luminescence in germanate glasses and fibers doped with transition metals (Cr, Ni), bismuth (Bi), and rare-earths (RE) has been investigated. In bismuth-doped GGB glasses, the influence of Sb2O3 content on luminescence properties has been studied, and the possibility of drawing glass into fiber. Luminescence at 1.3 μm with FWHM=209 nm was observed for the glass doped with 3 mol% Sb2O3 and 1.5 mol% Bi2O3. In the next step, the spectroscopic properties of Cr³⁺ doped GGB glass and optical fiber were investigated. After drawing glass into fiber FWHM (full with at half maximum) at 1.0 μm increased from 202 nm to 234 nm compared to bulk glass. Obtained luminescence at 1.0 μm can be attributed to the ⁴T₂ → ⁴A₂ transition of Cr³⁺ ions. For multicore glass-ceramic optical fiber, broadband near-infrared emission in the range of 1.1 to 2.1 μm was obtained under 940 and 980 nm pump excitation as a superposition of luminescence bands of Ni²⁺, Er³⁺, Tm³⁺ and Ho³⁺ ions.