Tm³⁺-doped barium antimony germanate glass fibers for achieving 1.8–2  µm lasers

Near- and mid-infrared fiber lasers at the ∼2µm wavelength range are essential for applications such as medical diagnostics, environmental monitoring, and military confrontation. However, developing materials that provide both anti-crystallization stability and high gain in this range remains challenging. This study presents the development of high-gain Tm 3+ -doped barium antimony germanate (BaO−Sb 2 O 3 −GeO 2 , abbreviated as BSG) glass fiber, designed to achieve laser emission at 1.8–2 µm. Based on the glass-forming region, the composition of BSG bulk glass is optimized, and it exhibits a high Tm 3+ doping concentration ( N =3.3×10 20 ions/cm 3 ), excellent anti-crystallization stability (Δ T =250 ∘ C), and a large emission cross-section ( σ e =8.4×10 −21 cm 2 ). Tm 3+ -doped BSG optical fibers are fabricated using a melting–quenching method with a large full width at half-maximum of up to 200 nm in their amplified spontaneous emission spectra. Such Tm 3+ -doped BSG fibers produced gain coefficients of 6.48 dB/cm at 1950 nm and 6.03 dB/cm at 1867 nm when pumped at 1570 nm, respectively. Furthermore, laser outputs of 1862 nm and 1964 nm are achieved using a 2 cm long Tm 3+ -doped BSG glass fiber, highlighting the potential of BSG glass fibers in near- and mid-infrared laser applications.