Deactivation effects of Tb³⁺ on Ho³⁺ emission in fluoroindate glasses for 3.9 μm laser applications

A series of Ho³⁺/Tb³⁺ co-doped fluoroindate glasses with good thermal stability have been synthesized to study the deactivation effects of Tb³⁺ on the Ho³⁺: 3.9 μm emission. Efficient 3.9 μm emission enhancement is obtained under excitation by an 888 nm laser diode (LD). The Judd-Ofelt (J-O) intensity parameters and radiative properties are calculated to evaluate the spectroscopic properties. Possible energy transfer processes resulting in emission reinforcement are discussed. A higher spontaneous transition probability and larger peak emission cross section are achieved with the inclusion of Tb³⁺. This analysis supports the conclusion that Ho³⁺/Tb³⁺ co-doped fluoroindate glass is a potentially useful laser material for highly efficient 3.9 μm fiber lasers.