In laser resonators laser medium is located between two mirrors. Laser emission is reflected many times between mirrors and enhanced during such process the part of the beam goes through a half-transmitting mirror. This part of the beam is used for laser treatment procedure.
For industrial treatment of materials two types of laser are used: Nd:YAG lasers and CO2 lasers. Nd:YAG laser is a solid type laser which active medium is an yttrium aluminium garnet rod alloyed with neodymium (Nd). CO2 laser is a gas type laser which uses carbon dioxide (CO2) as an active medium. .
Nd:YAG lasers feature great output power up to 5 kW and can be used for welding, marking, punching etc.
One of the advantages of the Nd:YAG lasers emission is their ability to transmit laser beam by means of fibre-optical components which can be easily transferred by robots.
CO2 lasers are much more powerful, up to 50 kW. As lens are not able to withstand more powerful beams, the mirrors with water cooling are used for cutting and surface treatment with the use of more powerful lasers.
Laser beam generation in CO2 lasers is based on gas use for CO2 lasers, nitrogen and helium. These gases shall be frequently replaced which supposes strict requirements for quality of gas used for CO2 laser and gas feeding system.
The lasers of these two types generate emission in infrared spectrum which means that laser beam is invisible. Operator shall take all necessary precautions and wear protective glasses while inspectors and other operators shall be protected by equipment enclosures. A low-powered laser of visible spectrum is often used for system adjustment.
Many other lasers can be used for generation of a wide range of wave lengths which cover almost the whole spectrum: from infrared to visible and ultraviolet spectrum. Each of these types has advantages as related to specific applications.
Nevertheless, due to laser beam power for materials treatment CO2 and Nd:YAG lasers are generally used.