6. Glossary

Green-gap (jump in green-yellow range)

This is the spectral range from around 500 to 600 nm, in which it is difficult to manufacture stable and efficient solid-state laser diodes with power levels in excess of a few hundred mW.

VUV (vacuum ultraviolet)

Spectral range corresponding to wavelengths below about 180 nm.

Rare earth ions

Trivalent lanthanide series ions (Ce ³⁺ to Yb ³⁺ ) from Mendeleev's table.

Transition (metal) ions

Iron-group transition (metal) ions in the di-, tri-, tetra- or even pentavalent state