Ultrabroadband mid-infrared emission and gas sensing of cobalt-doped chalcogenide glass ceramics

Mid-infrared (MIR) gain materials are of great significance for the development of MIR tunable fiber lasers. Herein, for the first time, to the best of our knowledge, it is found that Ga₂Se₃ nanocrystals distributed in chalcogenide glass ceramics can provide new tetrahedral-coordinated sites that can be used to activate ultrabroadband MIR emissions of divalent transition metal ions, such as Co²⁺. Under the excitation of a 1550 nm diode laser, the transparent Ge-Ga-Se glass ceramic embedded with Co²⁺: Ga₂Se₃ nanocrystals shows an intense 2.5-5.5 µm ultrabroadband emission. The peak wavelength is located at ∼4.2 µm and the full width at half maximum exceeds 2 µm. Such emission properties, originating from the dual lattice sites of Ga³⁺ ions, are superior to those of transparent chalcogenide glass ceramics embedded with Co²⁺: ZnSe nanocrystals. Moreover, the gas detection system built based on the glass ceramic shows a sensitivity of 45.9 ppm for butane gas. Therefore, the chalcogenide glass ceramics embedded with active Co²⁺: Ga₂Se₃ nanocrystals have great potential in MIR tunable fiber lasers and gas sensing.