ABSTRACT
Colour centres (CCs) exist in many types of crystalline solids, including both ionic and covalently bonded lattices. In table B1.8.1, the major physico-chemical, optical and mechanical characteristics of the crystal hosts intended for CC laser-active elements are considered and compared with each other and with other wellknown laser media. The most promising materials for developing CCs are crystals of alkali-halide metals, alkali-earth fluorides, oxides (for instance, sapphire) and covalent crystals (at present the only available representative is diamond).
