What Is a YAG Laser?
A YAG laser is a solid-state laser that uses crystals of yttrium (Yttrium), aluminum (Aluminum), and garnet (Garnet).
Principle of YAG Lasers
LASER stands for “Light Amplification by Stimulated Emission of Radiation” in English.
First, energy is applied externally to a YAG crystal using a flash lamp or laser semiconductor. This causes the electrons in the crystal to move from the lower to the upper level and enter an excited state.
After a short time, the excited electrons attempt to return to the ground state (transition), emitting light in the process. The emitted light hits other electrons in the excited state, causing them to transition in the same way, which results in further light emission. This is called induced emission.
The wavelength and characteristics of the light emitted depend on the rare earth elements doped into the YAG crystal. The most commonly used YAG lasers are Nd: YAG lasers doped with neodymium (Nd) and Er: YAG lasers doped with erbium (Er), and the doping element is selected according to the wavelength to be emitted.
The fundamental wavelength of the widely used Nd: YAG laser is 1064 nm, and when passed through a nonlinear optical crystal, light at 532 nm, the second harmonic, and 355 nm, the third harmonic, can also be extracted.
Applications of YAG Lasers
YAG lasers are widely used in the research, industrial, and medical fields.
In the industrial field, they are used for microfabrication, marking, trimming, metal welding, and cutting. Nd: YAG and Yb: YAG lasers are particularly popular for welding and other applications.
In the medical field, they are widely used for cataract treatment in ophthalmology, removal of spots and birthmarks in cosmetic dermatology, and abscess incision and cavity treatment in dentistry.
Cautions When Using the YAG Laser
The Er: YAG laser is a mid-infrared laser with a wavelength of 2.94 μm. It is a highly safe laser that has low tissue penetration and is absorbed by surfaces. However, Er: YAG lasers are invisible to the eye, although they reflect off mirrors and metals. Therefore, protective goggles specially designed for the Er: YAG laser must be worn by everyone present during use. Always make sure that the power is turned on and off and that there are no unrelated people in the vicinity before using the laser.
Always be aware of your surroundings so that you do not focus your attention only on the area to be irradiated by the laser, and never irradiate unrelated areas to avoid accidents.