Name
Uniformity Control of Optical Precision Coatings on 2D and 3D Components
Date
Monday, May 8, 2023
Time
2:50 PM - 3:10 PM
Description
Chris Britze1, Michael Vergöhl1, Andreas Pflug1, Thomas Melzig1, Stefan Bruns1, Philipp Henning1, Ulrike Fuchs2, Sebastian Kaldun2, Jörg Terhürne3, Grit Hüttl4, Daniel Hofmann4, Klaus Mann5, Bernd Schäfer5, Thomas Schütte 6, Rolf Schäfer7, Klaus Nauenburg7, Tobias Radny7, Uwe Richter8
1 Fraunhofer Institute for Surface Engineering and Thin Films IST, Braunschweig, Germany; 2asphericon GmbH, Jena, Germany; 3Bte-Bedampfungstechnik GmbH, Elsoff, Germany; 4GfE Fremat GmbH, Brand-Erbisdorf, Germany; 5IFNano Institut für Nanophotonik Göttingen e.V., Göttingen, Germany; 6PLASUS GmbH, Mering, Germany; 7robeko GmbH & Co. KG, Mehlingen, Germany; 8SENTECH Instruments GmbH, Berlin, Germany
Optical components are an essential part of a large variety of modern products with electro-optical functionality. Their applications range from machine vision, industry 4.0, medical and bioprocess engineering to space applications. Due to the trend towards higher complexity of optical products, the coating deposition onto two-dimensional and three-dimensional substrates becomes increasingly challenging. With conventional coatings, a very broad-band antireflection coating on curved substrates can consist of more than 100 individual layers. Other filters such as bandpass filters have an annoying central wavelength shift with such coatings. A gradient specifically applied to the uniformity profile can be mandatory to maintain the wavelength of spectral features at different substrate positions, which are affected by gradients that occur naturally in PVD processes and by varying angles of incidence. Gradient filters also play an increasing role for flat components such as pixel filters used in hyperspectral cameras. With the help of a digital twin derived from physical modelling of the plasma and gas flow dynamics in the reactor, it is possible to precisely predict and set the gradients on the individual surface geometries. Additional in-situ characterization techniques were implemented in industrial coating systems, including an in-situ gradient measurement using a hyperspectral camera for the first time. In addition, spatially resolved optical emission spectroscopy reveals a change in the plasma composition for longer processes, which contributes to the optimization of long-term coatings. Furthermore, in-situ measurements directly on the coated components are implemented. Fast moving substrates in combination with curved surfaces result in a particularly challenging measurement procedure. A special in-situ reflection measurement with an integrating sphere was therefore developed. Finally, a relatively new coating technique is the use of rotatable sputter targets for precision optical coatings. Here, various new target materials, movable magnet bars and assisting microwave sources were investigated, which enable a further improvement of the layer properties. This work was funded by the German Federal Ministry of Education and Research (BMBF) within the joint research project “EPIC Lens”.
1 Fraunhofer Institute for Surface Engineering and Thin Films IST, Braunschweig, Germany; 2asphericon GmbH, Jena, Germany; 3Bte-Bedampfungstechnik GmbH, Elsoff, Germany; 4GfE Fremat GmbH, Brand-Erbisdorf, Germany; 5IFNano Institut für Nanophotonik Göttingen e.V., Göttingen, Germany; 6PLASUS GmbH, Mering, Germany; 7robeko GmbH & Co. KG, Mehlingen, Germany; 8SENTECH Instruments GmbH, Berlin, Germany
Optical components are an essential part of a large variety of modern products with electro-optical functionality. Their applications range from machine vision, industry 4.0, medical and bioprocess engineering to space applications. Due to the trend towards higher complexity of optical products, the coating deposition onto two-dimensional and three-dimensional substrates becomes increasingly challenging. With conventional coatings, a very broad-band antireflection coating on curved substrates can consist of more than 100 individual layers. Other filters such as bandpass filters have an annoying central wavelength shift with such coatings. A gradient specifically applied to the uniformity profile can be mandatory to maintain the wavelength of spectral features at different substrate positions, which are affected by gradients that occur naturally in PVD processes and by varying angles of incidence. Gradient filters also play an increasing role for flat components such as pixel filters used in hyperspectral cameras. With the help of a digital twin derived from physical modelling of the plasma and gas flow dynamics in the reactor, it is possible to precisely predict and set the gradients on the individual surface geometries. Additional in-situ characterization techniques were implemented in industrial coating systems, including an in-situ gradient measurement using a hyperspectral camera for the first time. In addition, spatially resolved optical emission spectroscopy reveals a change in the plasma composition for longer processes, which contributes to the optimization of long-term coatings. Furthermore, in-situ measurements directly on the coated components are implemented. Fast moving substrates in combination with curved surfaces result in a particularly challenging measurement procedure. A special in-situ reflection measurement with an integrating sphere was therefore developed. Finally, a relatively new coating technique is the use of rotatable sputter targets for precision optical coatings. Here, various new target materials, movable magnet bars and assisting microwave sources were investigated, which enable a further improvement of the layer properties. This work was funded by the German Federal Ministry of Education and Research (BMBF) within the joint research project “EPIC Lens”.
Speakers
Chris Britze - Fraunhofer IST