Used as a dopant in optical fibers and fiber amplifiers for telecommunications, particularly in the C-band and L-band wavelength ranges. Plays a role in solid-state lasers and upconversion materials due to its luminescent properties. Serves as a catalyst in organic synthesis reactions, especially in coupling and cyclization processes. Employed in research for developing infrared-emitting materials and in the preparation of other erbium-containing compounds for electronic and photonic applications.