To manufacture optics and optical components, the institutes of the Fraunhofer Group for Light & Surfaces have various processes for shaping and coating at their disposal. Fraunhofer IOF produces metal mirrors, gratings and plastic-based lenses and lens arrays using ultra-precision machining. For applications requiring the wavelength range from 6 nm to 14 μm, it uses diamond tools for machining metal, crystal and plastic optics. To correct the diamond-treated surfaces, Fraunhofer IOF uses magnetorheological finishing (MRF). As a result, complex surfaces (aspheres, optical freeform surfaces, arrays) can be produced with pinpoint accuracy.
Lithographic techniques allow Fraunhofer IOF to produce a large number of elements with the highest lateral accuracy – an important prerequisite for micro-optics integration on the wafer scale. As an extremely flexible direct-writing process, mask-free grayscale lithography enables the generation of highly precise micro-optic elements, microstructures and surface profiles.
Fraunhofer IOF produces microlens arrays using reflow of photoresists and subsequent transfer via reactive ion etching (RIE), here as an established technology. To replicate micro-optics, the institute deploys UV molding to produce micro-optics on the wafer scale. For this purpose, liquid polymer resin is UV hardened in a contact-mask aligner between a substrate (for example, a glass or semiconductor wafer) and a transparent embossing tool.
To coat optics, Fraunhofer IST has developed and constructed the coating platform EOSS® – a new system to deposit sophisticated optical coatings. In this case, not only can extremely low-defect coatings be produced, but complicated layer designs with a great number of layers can also be achieved with an extremely precise and uniform coating. Using EOSS®, Fraunhofer IST could show that the design with rotatable cathodes and optimized sputtering targets is excellently suited for producing homogeneous optical filter coatings, which are extremely stable over a period of many weeks.
In addition, Fraunhofer FEP develops processes and technologies to apply electrical, optical, acoustic or magnetically effective layers and layer systems onto large areas with vacuum processes precisely and homogeneously. This way, it lays the foundations for new products in the sectors of optics, electronics and sensor technology, photovoltaics, storage media and biomedical engineering. For their customers, the institutes develop cost-effective technologies to produce innovative products, for which the combination of different layer properties essentially determines the product properties. The long-term stable sputtering processes are suitable for the production of precision coating systems. The services the group’s institutes offer include the adapted development of key assemblies, processes and coating systems up to the scale-up and transfer of integrated packages from hardware and technology into production. Examples for this are:
- Layer systems and gradient layers for precise optical components (filters, mirrors)
- Antireflective and antireflective-antistatic coatings of optical components with high demands on stress reduction and climatic resistance (eyeglass lenses, optics)
- Layers and layer systems for magnetic and optical storage media (hard disks, CD, DVD)
- Piezoelectric layers for ultrasound microscopy as well as for microenergy production
- SixOyNz antireflective coating systems for eyeglass lenses
- SixOyNz gradient layer systems for rugate filters or IR edge filters