In most laser machines, one or several mirrors are used to forward the laser beam from the cavity to the working head. Usually, each mirror deflects the laser beam at an angle of 90°, corresponding to an angle of incidence of 45°. At these mirrors, reflectance should be as high as possible in order to minimize loss of laser power. In addition, phase shift between the s- and p-polarized components of the reflected beam should be as low as possible in order to avoid disturbing the polarization of the laser beam. Mirrors with such properties are called zero-phase mirrors

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 CO₂ laser mirrors. Therefore, copper mirrors are preferred if best-possible cooling is important, for example in CO₂ laser machines with very high laser power.

The optical properties of a mirror (reflectance, phase shift, etc.) are determined by its coating. In order to realize different mirror functions, different coatings are needed.

The new Zero Phase Shift High Reflection (ZPS-HR) coating features lower absorption by 40% compared to standard ZPS/TRZ coating. Maximum absorption of the ZPS-HR version coating is 0.3%, an improvement to the standard ZPS absorption level of 0.5%.

MMR-P coating can be used for zero phase shift mirror or cavity optics, and allows for the highest total random polarization reflection available. It can also be applied to a level-changing mirror in two-tiered resonator systems. Our MMR-P coating keeps the same capabilities of phase shift and high reflection of visible light to enable clear observation of HeNe laser or diode laser beam reflection for alignment, location indication, etc.