Broadband NIR luminescence in double-core germanate optical fiber

In the paper, 1.4 – 2.2 μm broadband emission under 796, 808, 980 nm laser diode excitation in low phonon energy germanate glass system co-doped with 0.7Er₂O₃/0.35Tmo₂O₃ (1st core) and 0.7Tm₂O₃/0.15Ho₂O₃ (2nd core) were investigated. Next, double-core, double-clad optical fiber has been developed by the modified rod-in-tube technique. Amplified spontaneous emission (ASE) in double-clad optical fiber with 3dB bandwidth was measured to be 346 nm and 677 nm for - 10 dB. ASE spectrum is a result of the partial donor-acceptor energy transfer and superposition of Er³⁺: 4I_13/2 → 4I_13/2, Tm³⁺: ³F₄ → ³H₆, 1.8 μm and (Ho^3+:5I₇ → ⁵I₈) 2 μm emission bands. Excellent spectroscopic properties indicate that the developed germanate optical fiber is a promising active element for construction compact, broadband ASE sources.