Laser beam welding is a joining technology in which the parts are joined in a molten state. Components made of materials that absorb laser radiation as described in sections 4.2 and 4.3 are usually welded using cw laser radiation; laser pulses are also used for short seams or spot welds. By using non-linear absorption mechanisms, which occur when applying ultrashort laser pulses, it is also possible to join workpieces that are otherwise transparent at the wavelength of the laser radiation used.