Pilot lasers are used in systems with invisible CO2 processing lasers to determine the beam’s point of impact. The beam guidance of both lasers is the same, which leads to problems: If the beam-guiding components are not optimized for the wavelengths used, they “swallow” light. In silicon mirrors, the light of the pilot laser was almost not visible anymore.
A novel dual-band coating on silicon substrates creates mirrors that offer high reflection values for the processing wavelength 10.6 µm and simultaneously reflects the light of red pilot lasers with a high yield. At an angle of incidence (AOI) of 45°, the following values can be achieved:
| R (10.6 µm) | > 99.8% |
| R (600-700 nm) | > 90.0% |
The low phase shift of approximately ±2° is also noteworthy.
In addition to silicon mirrors, copper mirrors are also used for light of the wavelength 10.6 µm. However, silicon substrates have major advantages: Unlike pure metal mirrors, they are significantly lighter. Furthermore, silicon mirrors are free of thorium and have a surface resistance that does not scratch as quickly during cleaning.
