UV lasers are called "UV laser markers" because their wavelength is one-third of the fundamental wavelength (1064nm) and because they fall within the ultraviolet region. They are also known as THG (Third Harmonic Generation) lasers. The fundamental wavelength is converted by a nonlinear crystal into a wavelength of 532nm plus the fundamental wavelength, which is then converted to 355nm by a separate single crystal. This method has a very high absorption rate for various materials, allowing marking and processing without generating thermal stress, hence the name "cold marking."

The wavelength of the laser light significantly affects the spot size. Since the UV wavelength (355nm) is one-third of the fundamental wavelength (1064nm), the spot size can be focused much smaller, enabling marking even in confined spaces.