By absorption of ultra violet radiation, electrons in Eu atoms can result in specific transitions within the atomic levels creating emissions of visible radiation that is called luminescence. Therefore, Europium has been widely used as dopant in glasses applied to lasers and other optoelectronic devices.
Europium Oxide (Eu2O3) is popularly used as a red phosphor in display technology and fluorescent lamps, as well as an activator for yttrium-based phosphors. In energy efficient fluorescent lighting, Europium provides not only the necessary red, but also the blue. Several commercial blue phosphors are based on europium.
Its luminescence effect has also been critical in medical, surgical and biochemical applications.
A latest report (Nature, 2015. DOI: 10.1038/nature14025) on Europium is its application in quantum hard Drive which can reliably store information for 6 hours; this could potentially allow sensitive quantum data to be stored to a hard disk-like device and transported around when further improved.