An Nd:YAG laser is a solid-state laser whose main emission line is near infrared at 1064nm. The host crystal is yttrium aluminium garnet. Typically, 0.5% - 3% of the yttrium atoms are replaced by neodymium (“doping”). This type of laser was developed in 1964 in Bell Laboratories. In addition to CO2 and fiber lasers, it is one of the most common and widely used types of lasers for industrial material processing.
For lasers with an average output power of up to about 100 watts, the excitation takes place via diode lasers that have a wavelength of 808nm (diode-pumped laser). The neodymium atoms are excited electronically, i.e. their electrons reach the higher energy level through absorption of the pump light. The energy stored in the excited atoms is released again by stimulated emission.
In the realisation of a solid-state body as a laser medium, usually the biggest technological challenge is: This solid-state body must be high-purity but selectively doped and, at best, monocrystalline. It should also implement supplied energy with the highest possible efficiency, thus minimising heat loss. A solid-state laser can be destroyed by its own gain at high pumping power. Therefore, the laser medium must be able to withstand the highest possible energy density.
The notation Nd:YAG means that in an yttrium-aluminium garnet crystal (chemically: Y3Al5O12) yttrium ions (chemical symbol: Y) have been replaced by neodymium (chemical symbol: Nd). With the Nd:YAG laser, the doping (degree of replacement) is between 0.5% - 3%. The higher the degree of doping, the higher the laser power, but the lower the beam quality. This conflict of objectives is true for all lasers.
Energy is supplied optically, i.e. the Nd:YAG crystal is illuminated. The neodymium ions (Nd3+) are excited electronically. Krypton arc lamps, halogen lamps, xenon flash lamps, light diodes or laser diodes are used as pump sources.