The physical principle of laser marking is based on Light Amplifaction by Simulated Emission of Radiation. In other words, the energy emitted by a source (eg arc lamp) onto an active source (eg Nd:Yag crystal) will be collected and concentrated between two opposing mirrors.
1 The oscillation of specific light particles (photons) that move between the mirrors generates a high power laser beam. Only part of this beam passes through the output mirror (typically 10 to 20%), the rest being reinjected for the amplification process : the laser beam is thus created.
2 The beam is deflected by two scanning mirrors, driven electronically and via software, thus enabling a very high scanning speed and exceptional positioning accuracy.
3 The flat field lens then concentrates the beam energy in a very tiny spot and greatly increases the power density on the surface to be marked.
The different markings can be classified in three categories :
Engraving with material removal (sublimation)
the energy is delivered with high peak power pulses so that the material is instantaneously removed without thermal side-effects on the parts.
Material annealing with surface color change
The energy is delivered with lower pulses, heating the material and changing the surface appearance. No material is removed.
Marking through layer removal
On coated material, the contrast is created by removing the top layer, thus showing the color of the base material.