In many devices, systems, and technologies, such as telescopes and light barriers, cameras and laser measurement technology, optical filters are used to ensure that the light is either reflected or transmitted based on its wavelength.
Researchers at the Karlsruhe Institute of Technology have developed innovative materials and process technologies to create such filters using an inkjet print. At Hannover Messe 2023, they demonstrated how to manufacture custom optical filters and mirrors in an energy-efficient and cost-effective manner.
“Optical mirrors and filters are needed wherever light is involved in your work,” Uli Lemmer is the head of KIT’s Light Technology Institute. “Until now, however, they have been manufactured in complex vacuum systems that consume a lot of energy and material and have a comparatively low throughput.”
The optical filters are made up of layers of nanometer thickness that are superimposed on each other. These layers usually consist of two different materials, with different thicknesses and diffractive index. The material is evaporated in conventional production over a wide area, resulting in material losses. These evaporation methods require very high temperatures, and therefore are very energy-intensive.
With their novel process, the research team intends to reduce manufacturing costs and flexibly adapt the product’s properties to the respective application. That’s why the researchers used inkjet printers to create inkjet optical filters (IJPOFs).
For this they used two inks specially designed for the task. Drop by drop, the first ink is applied until the desired layer thickness has been reached. The product is then cured using UV light. The second layer is created using the exact same method. Inkjets create optical filters using two materials, which are alternately applied.
Researchers have identified spectroscopic procedures for medical use, metrological devices in the chemical industry or telescopes that require a large amount of reflectance.
The team created dielectric and optical mirrors using the new inkjet printing technology. These filters feature a reflectance of 99% with custom optical properties. This manufacturing technique is ideal for micrometer-sized optical components, such as those used in cameras. It can also be applied to large surfaces, like PV modules.
Uli Lemmer’s doctoral researchers and he aim to take this innovative technology, for the production and manufacture of a new-generation of optical filters and reflectors, to commercial success through a spinoff.