Singly Ho3+-doped tantalum tellurite glass and optical fiber for 2 μm fiber lasers

Singly Ho ³⁺-doped TeO ₂–Ta ₂O ₅ –ZnO (TTZ) glass and optical fiber for 2 μm fiber lasers have been investigated. The glass-forming region of the ternary TTZ glass system is determined to study its glass-forming ability and to select an appropriate glass matrix for doping Ho ³⁺ ions. Upon the excitation of a 1940 nm laser diode (LD), an intense emission at 2.06 μm with a full width at half maximum (FWHM) of 61 nm is observed from the Ho ³⁺-doped TTZ glass. The measured lifetime of the Ho ³⁺: ⁵I ₇ level in TTZ glass shows a gradual decrease from 3.5 to 0.98 ms as the dopant concentrations increase from 0.2 to 2 mol%. A large emission cross-section (σ _e ^MC ∼ 4.56 × 10 ⁻²¹ cm ²) and figure of merit (FOM, ∼ 6.83 × 10 ⁻²⁴ cm ²·s) are obtained. The Ho ³⁺ -doped TTZ glass is further fabricated into an optical fiber with an average transmission loss of 0.12 dB/cm at 1310 nm. The results show that singly Ho ³⁺ -doped TTZ glass and optical fiber are promising candidates for efficient 2 μm fiber lasers.