Used as a precursor in sol-gel processes for preparing erbium-doped optical materials, particularly in the fabrication of photonic devices such as fiber amplifiers and waveguides. Its ability to incorporate erbium ions into glass or ceramic matrices enables efficient luminescence at around 1.5 μm, which is critical for telecommunications applications. Also employed in the synthesis of thin films for integrated optics and laser technologies due to its good reactivity and volatility in deposition techniques like chemical vapor deposition (CVD).