DOC is a coating technology that combines a CVD diamond-like carbon (DLC) film and a physical vapor deposition (PVD) coating in a custom coating chamber. DOC coatings combine the best attributes of DLC and PVD, while minimizing their disadvantages. Traditional PVD IR coatings on windows, lenses and mirrors have good optical properties, but are relatively soft, making them easily scratched during cleaning and handling. DLC coatings are extremely durable but have limited optical performance, bandwidth and higher absorption losses. DOC is not quite as hard or durable as DLC, because it is relatively thin. However, DOC is harder and more durable than standard PVD films. The advantage of DOC is that it is able to be integrated into the optical coating design. This allows coatings to be designed with similar performance to a traditional PVD film, but with much improved durability. Many demanding applications from aerospace to 3D printing have found DOC to be a good solution. In this paper various applications that incorporate DLC or PVD coated optics will be compared with DOC coating alternatives, providing insight for possible solutions using this new technology.
Studies were made of the origins of defects in multilayer coatings used as high reflectors in the infrared, with the aim
of reducing the numbers of defects and increasing the laser-damage threshold for the coatings. Clean-room conditions were
found to be essential for cleaning and coating low-defect substrates. The levels ofsurface and subsurface defects on the substrate
were the most important parameters in determining defects on a completed coating. Although the initial chromium film on the
silicon substrate appeared to contribute many defects, it was actually making visible submicron defects that were already on the
substrates. When the vacuum coating system was operated under clean conditions, the multilayer coatings added few defects
to ones already present. Defect densities were reduced by a factor of 100 during the course of the study, resulting in a significant
improvement in the laser-damage threshold of the coatings.