In the beam delivery section of a laser working machine, the laser beam is transferred from the laser cavity to the working head. In principle, two moveable mirrors would be sufficient in a 2D-machine for guiding the laser beam to any point on the worksheet. In modern 2D-machines and especially in 3Dmachines, however, the beam delivery section has additional functions which require additional mirrors with specific properties.
In order to optimize function of these mirrors, different substrate materials are used - the most common ones are silicon(Si) and copper (Cu). Silicon mirrors have light weight and are therefore preferred in flying optics where high accelerations are needed. Copper has high thermal conductivity, and channels for cooling water can be included directly into the mirrors. Therefore, copper mirrors are preferred if best-possible cooling is important, for example in machines with very high laser power. - The optical properties of a mirror (reflectance, phase shift, etc) are determined by its coating. So in order to realize different mirror functions, different coatings are needed.