YAG (Yttrium Aluminium Garnet, Yttrium Aluminium Oxide Y3Al5O12) is a durable, synthetic material belonging to the garnet group. It can be used as an alternative to sapphire, both being easier to polish and not exhibiting the latter’s birefringence. YAG is frequently used in solid state laser systems where doping with certain rare elements such as neodymium and erbium to improve performance, e.g. Nd:YAG, Er:YAG, etc. Undoped YAG transmits between 0.21-5.5μm.
YAG is typically used as an active laser crystal when doped, but its durability and optical properties mean it can also be used as an optical material in place of sapphire. YAG lasers have a broad range of applications, from ophthalmology and medical laser to laser range finding equipment.
