Infrared radiation properties of Ho³⁺ in multicomponent germanium tellurite glasses

Ho³⁺-doped and Ho³⁺/Yb³⁺-codoped multicomponent germanium tellurite (MGT) glasses with multifarious emission channels in the near-infrared wavelength region have been fabricated and characterized. Judd-Ofelt intensity parameters of Ho³⁺-doped MGT glasses are solved to be Ω₂ = 5.32 × 10^-20 cm², Ω₄ = 2.73 × 10^-20 cm², and Ω₆ = 1.12 × 10^-20 cm², indicating a higher asymmetric and stronger covalent environment around Ho³⁺ ions in MGT glasses. Efficient infrared fluorescences have been observed in MGT glasses, and spontaneous emission probabilities are derived to be 230.4, 79.9, and 138.3 s^-1 for the ⁵I₆ → ⁵I₈, (⁵F₄,⁵S₂) → ⁵I₅, and ⁵I₇ → ⁵I₈ radiative transitions, respectively. In Ho³⁺/Yb³⁺-codoped MGT glasses, the maximum stimulated emission cross-section of 2.0 μm emission is calculated to be 4.93 × 10^-21 cm², and the corresponding gain cross-section is derived to be 3.62 × 10^-21 cm² when the excited state population fraction P reaches 0.8. Multifarious infrared emissions show that Ho³⁺ in MGT glasses is a good candidate for optical amplifiers and optoelectronic devices.