Used as a dopant in optical fibers and fiber amplifiers, particularly in the telecommunications industry where it enhances signal transmission in the C-band and L-band of infrared light. Plays a role in the production of upconversion materials that convert low-energy photons to higher-energy emissions, useful in bioimaging and display technologies. Employed in research settings for developing luminescent compounds and sensors due to its favorable emission properties in the near-infrared range. Also utilized in catalytic applications and as a precursor for synthesizing other erbium-containing compounds in solid-state chemistry.