Er: YAG is a kind of excellent 2.94 um laser crystal, widely used in laser medical system and other fields. Er: YAG crystal laser is the most important material of 3nm laser, and the slope with high efficiency, can work at room temperature laser, laser wavelength is within the scope of the human eye safety band, etc. 2.94 mm Er: YAG laser has been widely used in medical field surgery, skin beauty, dental treatment.