Tm^3+-doped tellurite glasses for fiber amplifiers in broadband optical communication at 120 µm wavelength region

Broadband emissions at around 1.20 and 1.46 μm wavelengths from thulium (Tm(3+))-doped tellurite glasses were observed under 465 nm wavelength excitation. The 1.20 μm emission originates from the Tm(3+): (1)G(4)-->(3)H(4) transition, and the associated stimulated peak emission cross-section is calculated to be 0.47 × 10(-20) cm(2). Population inversion occurs between the (1)G(4) and (3)H(4) levels, and a positive gain band from 1.20 to 1.28 μm is achieved at relatively low Tm(3+) dopant concentration. Our results suggest that this glass system is promising for optical fiber amplifiers operating at the relatively unexplored low loss 1.20 μm wavelength region.