Mid-Infrared Emission from Tm ³⁺ -Doped Perovskite Fluoride Glasses Enabled by Host Structure Engineering and Gas Sensing Applications

Rare-earth perovskites have been widely investigated for their flexible optical properties and promising prospects in mid-infrared (MIR) applications. However, the structure-dependent luminescence behavior of rare-earth ions is still not fully understood, making emission regulation challenging. In this work, Tm3+ was introduced into three structural types of perovskites – Cs2ZnCl4, CsPbCl3, and CsPbBr3 – and stabilized within a ZBLAN (ZrF4–BaF2–LaF3–AlF3–NaF) fluoride glass matrix. Under 793 nm excitation, Cs2Zn0.85Tm0.15Cl4-ZBLAN and CsPb0.85Tm0.15Cl3-ZBLAN exhibited enhanced emission at 1.47 μm, while CsPb0.85Tm0.15Br3-ZBLAN showed stronger enhancement at 1.67 μm, with additional emissions at 2.37 and 3.46 μm. These results demonstrate that the host crystal structure has a significant influence on the mid-infrared emission performance of Tm3+ ions. XRD and XPS analysis revealed the influence of lattice distortion, and a prototype HCl gas sensor highlighted the potential of Tm3+ perovskite fluoride glasses as broadband MIR emitters for practical sensing applications.