2.7 µm Mid‐Infrared Emission in Highly Erbium‐Doped Lanthanum Gallate Glasses Prepared Via an Aerodynamic Levitation Technique

Abstract Highly Er³⁺‐doped La₂O₃–Ga₂O₃ glasses up to ≈5.85 × 10²¹ cm⁻³ in Er³⁺ concentration are synthesized by an aerodynamic levitation technique. The glasses are characterized by high glass‐transition temperatures, low OH⁻ absorptions, and long infrared cut‐off wavelengths. Judd–Ofelt analysis reveals a large radiative transition rate and a high branching ratio of the ⁴I_11/2 → ⁴I_13/2 transition, e.g., 46 s⁻¹ and 21%, respectively, at 10 mol% Er₂O₃. The intensity of 2.7 µm emission drastically increases with increasing Er₂O₃ content and reaches a maximum at 10 mol% Er₂O₃. By contrast, the intensity of the 1.5 µm emission decreases with increasing Er₂O₃ content when the Er₂O₃ content is greater than 1 mol%. The emission cross‐section and the gain bandwidth at 2.7 µm are as large as 9.05 × 10⁻²¹ cm² and 9.19 × 10⁻²⁶ cm³ at 10 mol% Er₂O₃, respectively. The upconversion spectra also indicate that the investigated glasses exhibit small multiphonon relaxation rates and large quenching concentrations.