Broadband near infrared photoluminescence of Cu²⁺-doped corundum (-Al₂O₃)

Copper-doped corundum (alpha-Al2O3) possesses an intense broadband photoluminescence in the near infrared. This photoluminescence is originated from Cu2+ ions, which substitute for Al3+ ions in corundum lattice. Co-doping with Ge is necessary to obtain the luminescent material. It seems, that simultaneous introduction of Ge is needed to provide the charge compensation for heterovalent Cu2+ -> Al3+ substitution, in such a way that the whole process (Cu2+, Ge4+) -> 2Al(3+) is charge-balanced. The broad photoluminescence spectrum matches well with transparency window of silica optical fibers and the quantum yield seems to be satisfactory, so copper-doped corundum can become demanded as a new active media for solid state lasers and amplifiers. This is the first example of photoluminescence from octahedrally coordinated Cu2+ ion in oxide materials.