The luminescent glasses are characterized by high mechanical and chemical stability. For optical activation, metal ions from the rare earth group, which have an element-specific emission spectrum, are added to the glass. The glasses are very flexible with regard to the type and level of doping, so different metal ions can easily be added to the glass. The complexity of the resulting emission spectrum, i.e. the fingerprint of the glass, can be significantly increased by double or multiple doping. The fingerprint depends not only on the type and amount of doping, but also on the excitation wavelength.

Depending on the excitation wavelength, the luminescent material changes color. "The multitude of possibilities in the combination of doping type and level opens up a new field of application for the use of the luminescent glasses: product marking. The resulting different spectra can thus ensure precise and individually desired tracking," says Prof. Dr. Schweizer, head of the Fraunhofer Application Center for Inorganic Phosphors in Soest.