Fabrication of chalcohalide glass ceramics containing BaCl ₂ : Er ³⁺ crystals for 3.1 µm mid‐infrared luminescence

Abstract The growing demand for high‐performance mid‐infrared (MIR) light sources has stimulated the development of rare earth ions activated chalcohalide glass ceramics (GCs). Herein, Er 3+ ‐doped GeS 2 –Ga 2 S 3 –CsCl–BaCl 2 chalcohalide glasses were fabricated via melt‐quenching, which shows good transparency spanning from visible to the MIR region. The controllable precipitation of BaCl 2 crystals through thermal annealing provides a low‐phonon‐energy environment for Er 3+ doping. Spectroscopic analysis demonstrates that Er 3+ ions preferentially partition into BaCl 2 , resulting in suppression of non‐radiative relaxation and enabling the appearance of uncommon emission lines of Er 3+ . Remarkably, in addition to 2.7 µm MIR emission, 3.1 µm MIR emission attributed to the Er 3+ : 4 S 3/2 → 4 F 9/2 transition was first reported in the chalcohalide glass system.