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

Abstract Highly Er 3+ ‐doped La 2 O 3 –Ga 2 O 3 glasses up to ≈5.85 × 10 21 cm −3 in Er 3+ 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 4 I 11/2 → 4 I 13/2 transition, e.g., 46 s −1 and 21%, respectively, at 10 mol% Er 2 O 3 . The intensity of 2.7 µm emission drastically increases with increasing Er 2 O 3 content and reaches a maximum at 10 mol% Er 2 O 3 . By contrast, the intensity of the 1.5 µm emission decreases with increasing Er 2 O 3 content when the Er 2 O 3 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 cm 2 and 9.19 × 10 −26 cm 3 at 10 mol% Er 2 O 3 , respectively. The upconversion spectra also indicate that the investigated glasses exhibit small multiphonon relaxation rates and large quenching concentrations.