The YAG laser

The laser-active medium of the YAG laser is an artificially grown YAG monocrystal (yttriumaluminum garnet = yttrium-aluminum crystal) that the neodyme (Nd:YAG) or ytterbium (Yt:YAG) is embedded in. Accordingly, the YAG laser is a solid-state laser that does not require any gas in order to generate laser radiation. The crystals are excited by light  energy from lamps or by radiation from laser diodes.