Used as a dopant in optical fibers and fiber amplifiers for telecommunications, particularly in the C-band and L-band wavelength ranges where signal amplification is critical. Plays a role in the production of specialty glasses with unique optical properties, including upconversion materials for infrared detection and display technologies. Employed in research settings for developing luminescent compounds and sensors due to its stable emission characteristics under excitation. Also utilized in nuclear applications as a neutron absorber in control rods or shielding materials because of its high neutron capture cross-section. Serves as a precursor in the synthesis of erbium-containing ceramics and oxides used in catalysis and electronic materials.