Undoped yttrium aluminum garnet is an optical material similar to sapphire. Undoped YAG is widely used in UV and IR optics due to its mechanical and chemical characteristics.

YAG has some excellent optical and other properties.

Nd:YAG crystal, which continues as the best of the rare earth garnet materials that are characterized by four-level laser operation which permits low threshold pulse and cw operation, is the most mature and widely used solid-state laser material adopted by R&D, medical, industrial and military customers.

Yb:YAG is one of the most promising laser-active materials and more suitable for diode-pumping than the traditional Nd-doped crystals.