Coatings / Job-Order Manufacturing

The optical characteristics of interference layer systems are determined by their thickness, their sequence and the dispersion characteristics of the individual layers. To model the transmission behavior of optical layer systems, commercial computer programs are available, which, if the material parameters are known, can produce and evaluate suggestions for the design, i.e. the structure of the layer stack. The software ‚SPEKTRUM‘, developed by the LZH, is tailor-made for industrial layer manufacturers (Fig. 1).Today, research on the fabrication of high-quality layer systems focuses on the development and optimization of adapted deposition processes and material combinations for desired applications. In industry, thermal deposition processes, in which the layers are deposited on the optic components using vacuum evaporation of the required material, still predominate the fabrication of layer systems.

Nevertheless, these processes cannot keep pace with the ever increasing quality demands of modern precision optics, and laser technology in particular (Fig. 2). For these demanding applications, improved process concepts (IAD: Ion-Assisted Deposition) have been developed, in which an additional low-energetic ion flow is applied to condensing. Due to impulse transfer, the coating molecules on the layer surface are given extra mobility and thus, they can migrate to the energetically most favorable position in the growing layer structure. As a consequence, the packing density of the layer increases, and this results in a much higher stability and improved optical characteristics, in comparison with layers conventionally deposited. A further improvement can be achieved using ion beam sputtering (IBS), in which the layer material is directly sputtered off a target by highly energetic ions. The layer systems produced by this process have the best structural and optical characteristics known today. Application-oriented optimization of optical functional layers includes the exact knowledge of the interaction of process parameters and the characteristics of the produced coatings. A further challenge is precise, online monitoring of the large number of process parameters.