Research for a Sustainable Future Annual Report 2023

Foreword Foreword Dear Readers, Laser technology spans an arc from the tiniest to the largest in our universe: from the nano and micrometer scale to the exploration of space. The laser can address the sheer breadth of this arc thanks to its unique properties: It can direct energy, concentrate it on the smallest volumes and create precisely defined energy densities. Its light decodes material compo- sitions, provides microscopic insights and transmits gigantic volumes of data around the globe. On the following pages, you can read about the dimensions our research at Fraunhofer ILT reached in 2023. In addition to our core business in materials processing and laser develop- ment, we have pushed forward into new fields of application in laser technology and optics: Cyber photonics is paving the way to making digital photonic production a reality by com- bining laser processes, data science and artificial intelligence. And as secondary sources, lasers generate X-ray, EUV and particle radiation for applications in semiconductor and medical technology. While these fields are already developing dynami- cally today, we are pursuing long-term strategies in quantum technology and energy generation from nuclear fusion; at the center of this are world-leading laser technologies and the expertise of Fraunhofer ILT and its partner network. New supply and process chains are needed to tap into the immense market volume of these future fields. Moreover, the photonics industry must reinvent itself. This applies in particular to laser-based inertial confinement fusion, which provides us with a fascinating interplay of dimensions: Pulsed high-energy lasers the size of three football fields concen- trate two megajoules of energy onto pinhead-sized beads containing a mixture of the hydrogen isotopes deuterium and tritium for just nanoseconds. The temperatures and pressures generated cause the hydrogen to fuse into helium and release enormous amounts of energy. We still have a lot of work to do before this technology can be used commercially. But 2023 was also a year of new beginnings for us. We are part of the multi-institutional STARFIRE Hub project, which aims to take laser-based inertial confinement fusion to a new level with the support of the US government under the leadership of the Lawrence Livermore National Laboratory. We are also playing a leading role in the BMBF’s Expert Commission on Fusion, which was set up at the same time as the world’s first fusion plasma was ignited in the USA at the end of 2022 and has been advising the German government ever since. We are also active at the forefront of quantum technology. Photonic solutions from our institute control individual atoms in quantum computers and sensors. In a strategic partnership with QuTech in Delft, we are laying the foundations for a quan- tum internet, and our laser technology has already enabled our partners to exchange entangled quanta via conventional telecom fibers between Delft and The Hague. A third quantum node is now being built in Aachen. In order to develop this market in its economic, political and social dimensions, the state government of NRW has entrusted Fraunhofer ILT with coordinating the Quantum Technologies Roadmap for NRW. For us, the trends outlined here are a great source of fascination! Fraunhofer ILT has positioned itself for the future in a compre- hensive strategy and structural process. The new structure gives even more weight to the combination of market intelli- gence and technological expertise. As the ONE team, we are full of innovative ideas that we would like to put into practice together with you. If we have piqued your interest, please contact our experts directly! We look forward to hearing from you. Cordially, Prof. Dr. rer. nat. Constantin Haefner 3

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Facts and Figures 2023 19 Granted Patents 48,5 Million General Budget (in Euro) 552 Employees 52 % Personnel Science, Technics, Administration 48 % Undergrad Assistants, Trainees, External Employees 7 7

Services of Fraunhofer ILT Alumni network Development of laser beam sources Components and systems for beam guiding and forming Packaging of optical high power components Modeling and simulation of optical components as well as laser processes Process development for laser materials processing, laser measurement technology, medical technology and biophotonics Process monitoring and control Solutions for digital production Model and test series Development, set-up and testing of pilot plants Development of X-ray, EUV and plasma systems Photonic components and systems for quantum technology Cooperations The Fraunhofer Institute for Laser Techno- logy ILT has partnerships with domestic and foreign companies and research centers in the field of laser technology so that it can offer its customers solutions from a single source. Fraunhofer ILT also maintains close contacts to universities, associations, chambers of commerce and trade, testing institutes and research ministries. Fraunhofer ILT and the associated chairs and subject areas of RWTH Aachen University sig- nificantly contribute to the qualified training and advanced training of young scientists in the field of laser technology. Thanks to their practical experience and in-depth insight into innovative developments, these employees are equipped with the best prerequisites to take up work in science and industry. They are, therefore, junior staff in demand. Since 2000, Fraunhofer ILT has been operating the alumni network Aix-Laser-People, which has over 500 alumni, to promote contact both with ILT employees and with each other. More than 80 percent of the alumni work in the manufacturing industry, many of them in laser-related industries, while 20 percent continue to work in science. Over 40 compa- nies have been founded by former employees in the last 30 years. By transferring innovative minds to industry and science, Fraunhofer ILT provides a direct benefit to society. In addition to the alumni network Aix-Laser-People, the association Arbeitskreis Lasertechnik AKL e.V., founded in 1990 by ILT executives, bundles the thematic interests of those who continue to work in the field of laser technology. With more than 550 employees and more than 19,500 m2 of net floor area, the Fraunhofer ILT is among the most significant research institutes in the field of laser technology worldwide. Contact Alumni network Dipl.-Phys. Axel Bauer (Alumni Manager) Phone +49 241 8906-194 axel.bauer@ilt.fraunhofer.de 9

Board of Trustees – Well Advised! The Board of Trustees advises the bodies of the Fraunhofer-Gesellschaft and the institute management and promotes contacts with industry and organizations interested in research In 2023, Dr Nicole de Boer, Isabel Hartung and Dr Jan Suhren were newly appointed to the Board of Trustees Members 2023 Dr Joseph Pankert Dr Reinhold E Achatz TRUMPF Photonic Components GmbH (Chairman) International Data Spaces Association Carl F Baasel Physicist Dr Nicole de Boer Bayern Innovativ GmbH Dipl-Volksw Isabel Hartung Senior Advisor Dipl-Ing Frank C Herzog Prof Ursula Keller Dipl-Ing Volker Krause Michael Lebrecht B Sc Prof Gerd Marowsky Manfred Nettekoven HZG Group ETH Zürich Laserline GmbH Mercedes-Benz AG Advanced Microfluidic Systems GmbH Chancellor of RWTH Aachen University Dr Stefan Ruppik Coherent Dr Torsten Scheller Dr Ulrich Steegmüller Dr Jan Suhren Prof Christiane Vaeßen Dr Hagen Zimer JENOPTIK Automatisierungstechnik GmbH ams-OSRAM International GmbH Federal Ministry of Education and Research Honorary Consul of the Kingdom of the Netherlands TRUMPF Laser GmbH The 38th Board of Trustees meeting was held on November 16 and 17, 2023 at Fraunhofer ILT in Aachen. 11

Facts and Figures Prof. Peter Loosen (Dep. Director untill 29.2.2024), Dr. Jochen Stollenwerk (Dep. Director since 1.3.2024) Dr. Vasvija Alagic-Keller (Comm. Director) Prof. Constantin Haefner (Director) Administration and Infrastructure Dr. Vasvija Alagic-Keller Information Technology / Administration / Construction and Workshops Joining and Cutting Laser Material Laser Powder Bed Dr. Alexander Olowinsky Deposition Dr. Thomas Schopphoven Fusion Dr. Tim Lantzsch Lasers and Optical Systems Dipl.-Ing. Hans-Dieter Hoffmann Joining of Metals Dr. André Häusler Additive Manufacturing and Repair LMD Min-Uh Ko M.Sc. LPBF Process and Systems Engeneering Niklas Prätzsch M.Sc. Optics Design and Diode Lasers Dr. Martin Traub Packaging Dr. Heinrich Faidel Joining of Plastics and Transp Materials Maximilian Brosda M.Eng. Coating LMD and Heat Treatment Viktor Glushych M.Sc. LPBF Application Development Dr. Tim Lantzsch (acting) Solid State Lasers Dipl.-Phys. Marco Höfer Ultrafast Lasers Dr. Peter Rußbüldt Cutting Dr. Frank Schneider AM Polymers Prof. Sebastian Bremen Fiber Lasers Patrick Baer M.Sc. NLO and Tunable Lasers Dr. Bernd Jungbluth EUV Technology Dr. Klaus Bergmann 13

Personnel 2023 Expenses 2023 Revenues over the last 10 years Mill € Facts and Figures 35 % Scientists 10 % Administrative staff 7 % Technical staff 37 % Undergraduate assistants 11 % Trainees / External emploees 52 % Staff costs 38 % Material costs 10 % Investments Basic financing by Fraunhofer Project revenues – industrial funding Project revenues – public funding 15

Spotlights 2023 More sustainable production using green lasers Integrated sensor technology in additive manufacturing 1 The mobile LIDAR system provides climate data in real time. 2 Electric snowmobile eSled with cold-resistant batteries, © Aurora Powertrains. Precise condition monitoring of machines and components is becoming increasingly important. Fraunhofer ILT has developed sensor infra- structure for intelligent industrial applications to collect sufficient amounts of data. Additively manufactured sensors are seamlessly integrated into components during the laser powder bed fusion (LPBF) manufacturing process. Real-time data provides insightful information about the load within the component – an important element of predictive maintenance. This opens up a wide range of applications, for example in toolmaking and mechanical engineering, in the automotive industry and in aerospace techno- logy. https://s.fhg.de/625 Contact: samuel.fink@ilt.fraunhofer.de Copper is the most important material for the production of core components for e-mobility. A research team from DESY, the Helmholtz- Zentrum Hereon, TRUMPF and Fraunhofer ILT has investigated which parameters are relevant for laser welding of high-performance electronics. High-speed images taken at the particle accelerator prove that using a laser with a green wavelength results in far fewer rejects, and significant savings can be made on raw materials. https://s.fhg.de/Rp9 Contact: alexander.olowinsky@ilt.fraunhofer.de New lasers for climate research Climate models require precise data from the atmosphere. A team from Fraunhofer ILT and the Leibniz Institute of Atmospheric Physics IAP has developed a compact and portable LIDAR (Light Detection And Ranging) system that can target individual atoms at altitudes of up to 100 km. LIDAR systems shoot laser beams into the sky and enable users to precisely collect wind and temperature data. The next step for the project partners is to transfer the LIDAR system to industry. https://s.fhg.de/Y7X Contact: michael.strotkamp@ilt.fraunhofer.de 1 Additively manufactured strain gauges integrated in a cutter head. 2 Laser beam welding of metal-ceramic substrates with green laser radiation. 17

Strategically Tackling the Future Market of Quantum Technologies "Quantum technology enriches the engineering toolbox immensely!" Dr. Bernd Jungbluth on non-linear optics, which contributes to entanglement exchange via classic telecom fibers between Delft and The Hague. According to QuTech, this is only possible thanks to Fraunhofer ILT‘s laser technology. In the next step, we will jointly build another node in Aachen. It will initially serve as a platform for testing and further deve- loping photonic components. The integration of such nodes is an exciting field of innovation - and ultimately, of course, we here in Aachen also want to become part of a global network as early as possible, which we are driving forward with our European partners in the Quantum Internet Alliance, among others. What role do networks play in opening up the quantum worlds? Networked thinking has always been the key to Fraunhofer ILT‘s success. We remain an institute for laser technology, but we strive to cooperate closely with players from quantum technologies. By exchanging ideas with them, we can opti- mally apply our solution expertise. Examples of this are the North Rhine-Westphalia Quantum Competence Network and the coordination of the quantum roadmap for the state, which Fraunhofer ILT recently took over. How do you rate the current state of affairs? In fact, we already have a very fertile quantum ecosystem in NRW with chairs at ten universities, including Siegen, Pader- born, Bonn and Aachen, the German Aerospace Center (DLR), Forschungszentrum Jülich, various Fraunhofer Institutes and a wealth of innovative SMEs, spin-offs and start-ups. The latter have a range from scalable semiconductor-based quantum computers developed by the young Aachen-based ARQUE Systems GmbH to ion trap-based quantum computers from Siegen-based eleQtron GmbH and Pixel Photonics GmbH from Münster, which is advancing single-photon detection with superconducting nanowires and photonic integrated circuits (PICs). Many of the players are based in the Aachen laser region. In the roadmap process, we are working closely with the EIN Quantum NRW office and Forschungszentrum Jülich. We want to involve as many stakeholders as possible and invite interested parties to contribute their expertise and ideas. We envisage a Center for Quantum Science and Engineering QSE in the Rhineland region as an anchor point. If we join forces, quantum technologies can and will make an important contri- bution to structural change in our region. Headline, 9 pt Contact Titel Vorname Name Geschäftsbereich XXX Dr. Bernd Jungbluth Tel. +49 12 3456-XXXX Haed of the Quantum Fax +49 12 3456-XXXX Technologies Strategic Program Mobil +49 12 3456-XXXX Phone +49 241 8906-414 vorname.name@ bernd.jungbluth@ilt.fraunhofer.de fraunhofer.de 19

Research Markets © CNES / Illustration David DUCROS, 2016. "The networking of different areas of expertise leads to symbioses and innovative laser solutions for new products." Contact Prof. Arnold Gillner Haed of the Department Business Development Research Markets Phone +49 241 89806-148 arnold.gillner@ilt.fraunhofer.de 21 new concepts. A central factor here is energy efficiency, particularly as mobile devices and the Internet of Things (IoT) are being used more and more. Fraunhofer ILT develops and evaluates beam sources for EUV lithography for such microelectronics and the correspond- ing measurement technology. Innovative electronic components for high-performance battery systems In addition to structure generation in the nanometer range, assembly and connection technology plays a decisive role for high-per- formance electronic components. Together with industrial partners, Fraunhofer ILT is developing new connection technologies for battery contacts and IGBT power components in order to integrate them into high-perfor- mance production systems. Fraunhofer ILT also has expertise in the structuring and functionalization of surfaces and in 3D volume structuring. For example, microscopic structures can be introduced into glass or sapphire substrates by selective laser etching, a technology that makes microfluidic systems for biochemical analyses possible. Aviation industry under pressure Aviation companies are looking for more environmentally friendly propulsion systems, sustainable fuels and energy-efficient tech- nologies. In turbine construction, there are many approaches for technical optimization and cost savings. Innovative turbine design, lighter turbine blades, optimized cooling and low-cost repair processes are just a few exam- ples. Scientists at Fraunhofer ILT are focusing primarily on additive manufacturing. The new additive manufacturing processes are also suitable for solving maintenance and repair problems. Robust laser technology for environmental satellites In the field of satellite-based measurement systems for environmental analysis, Fraun- hofer ILT offers powerful, narrow-band laser systems that researchers can use to detect the concentrations of gas components in the atmosphere with high accuracy. Together with partners such as the German Aerospace Center DLR, the Airbus Group, TESAT Space- com and the European Space Agency ESA, the institute has developed its own technology platform for satellite-based laser systems.

Research Results 2023 Research Results 2023 Fraunhofer ILT is one of the world‘s most important contract research and development institutes in laser development and laser applications. Customers from research and industry benefit from its extensive expertise and valuable know-how in the fields of lasers, optical systems, quantum technology, laser measurement technology, additive manufacturing, surface technology, joining and cutting, digitalization, EUV and plasma technology, and medical technology. Our core competencies include developing new laser beam sources and components, laser measurement and testing technology, and laser manufacturing technology. In the following you will find excerpts of our current research projects: Data Science and Measurement Technology Department – Process Control and System Technology Group – Material Analysis Group – Computational Methods Group Surface Technology and Ablation Department – Micro and Nano Structuring Group – Thin Film Processing Group – Polishing Group – In-Volume-Structuring and Lithography Laser Medical Technology and Biophotonics Department – Laser Medical Technology and Bioanalytics Group – Biofabrication Group Joining and Cutting Department – Joining of Metals Group – Joining of Plastics and Transparent Materials Group – Cutting Group Laser Material Deposition Department – Additive Manufacturing and Repair LMD Group – Coating LMD and Heat Treatment Group Laser Powder Bed Fusion Department – LPBF Process and Systems Engineering Group – LPBF Application Development Group – AM Polymers Group Lasers and Optical Systems Department – Optics Design and Diode Lasers Group – Solid State Lasers Group – Fiber Lasers Group – EUV Technology Group – Packaging Group – Ultrafast Lasers Group – NLO and Tunable Lasers Group 23

Data Science and Measurement Technology The interdisciplinary team at ILT researches and develops models, software and systems that link the real and digital worlds to unlock intelligent cyber-photonic systems in production and digital business models New methods and algorithms based on artificial intelligence play a central role for process monitoring, self-learning systems and in measurement technology The Data Science and Measurement Technology department takes an integrated approach to increasing productivity, efficiency and quality for laser-based manufacturing and metrology. We research and develop digital solutions in com- bination with customized laser beam sources, optical systems, sensors and systems engineering to make innovative production and measurement technology possible. For this purpose, we utilize methods from artificial intelligence to analyze sensor and image data as well as to adapt processes for self-learning laser systems. In the field of material analytics, we develop systems that classify materials for recycling and the circular economy. For our customers, we enable disruptive innovations and digitalization in photonics with our expertise in data science, modeling and metrology. Contact Prof Carlo Holly Head of Department Phone +49 241 8906-142 carlo.holly@ilt.fraunhofer.de Data Science and Measurement Technology Department Process Control and System Technology Material Analysis Computational Methods 25 25

AIRISE – AI applications in manufacturing 1 Quality assessment on the basis of production data, © Stephen Dawson / Unsplash. 2 Laser cutting in production, © Clayton Cardinalli / Unsplash. Using AI for more efficiency in production Efficiency in production is largely determined by process time and non-productive times. The focus is on preventing errors and detecting quality deviations at an early stage, two aspects that benefit greatly from artificial intelligence (AI). The use of preconditioned models with minimal training can quickly lead to initial results. In many cases, however, industry faces challenges both identifying data sources as well as selecting and applying them in an industrial environment. Jointly developing AI applications strengthens the employees involved as well as the entire company; it involves everyone affected when the AI solution envisaged is implemented. Based on the ALTAI procedure developed at European level, this process is adapted to the specific conditions and needs of small and medium-sized enterprises (SMEs) as part of AIRISE. Companies can access this program via public calls for pro- posals at www.airise.eu. AIRISE is supported by the EU with funds from the Horizon Europe research program under the funding code GA 101092312. Individual support in using AI The AIRISE project supports users by identifying suitable data sources, implementing sensor systems and data interfaces and using AI-based analysis results to optimize production. Across the entire value chain, defining objectives and monitoring success are at the center of the activities. AI in production Engineers with expertise in both manufacturing and AI look at the current issues in their company’s manufacturing environ- ment and then outline solutions that they then pursue together with the company's employees. Author: Ulrich Thombansen M. Sc., ulrich.thombansen@ilt.fraunhofer.de Contact Dipl-Ing Peter Abels Group Manager Process Control and System Technology Phone +49 241 8906-428 peter.abels@ilt.fraunhofer.de 27

Inline LIBS sensor in the metal recycling industry 1 LIBS measurements of steel chips. To extract metals from geological deposits, the mining industry consumes a significant proportion of global resources and energy. There is enormous potential to save on these resources when secondary materials containing such metals are recovered and then reused for production. To do this efficiently, the re- cycling industry, however, needs to know the composition of the input material to efficiently control the remelting process. Isolated scrap parts can be analyzed quickly and accurately using laser-induced breakdown spectroscopy (LIBS) and sorted according to metal types and even individual alloys. Fraunhofer ILT has been instrumental in developing the technology required for this in recent years. However, there are a large number of materials that are not suitable for automatic sorting. Testing in the metal industry The developed inline LIBS sensor has already been success- fully tested in companies that melt down scrap material on an industrial scale to recover the base metals steel, aluminum and lead. As the system quickly records the composition of fine- grained bulk materials, e.g. in transport containers or on con- veyor belts, it can chemically characterize the diverse metallic and metal-containing input materials such as slag directly upon delivery and then sort them together – based on scrap-mix optimization models – for the furnace process. The work was carried out as part of the EU project REVaMP under the funding code 869882. Monitoring variable material flows In collaboration with project partners, Fraunhofer ILT has developed and tested a LIBS sensor for use in existing recy- cling processes. The institute has combined the continuous automatic sampling by the LIBS process with upstream optical geometry detection. By intelligently evaluating the surface structure, the sensor distribute a grid of measuring points across the material in such a way that each laser pulse can be applied in a targeted manner and the material’s composition recorded as representatively as possible. Author: Dr. Cord Fricke-Begemann, cord.fricke-begemann@ilt.fraunhofer.de Contact Dr Cord Fricke-Begemann Group Manager Material Analysis Phone +49 241 8906-196 cord.fricke-begemann@ilt.fraunhofer.de 29

Simulation-based analysis of the ablation of thin transparent layers 1 Simulated temperature distribution in a transparent thin film. 2 Simulated expansion distribution in a transparent thin film As the resolution of displays constantly increases and size of integrated circuits decreases, industry needs precise laser mate- rial processing of thin, transparent and semiconducting layers for displays and semiconductors. Depending on the application, the layers consist, for example, of low-κ materials, indium tin oxide (ITO), silicon dioxide (SiO2) or silicon nitride (Si3N4) with layer thicknesses ranging from a few tens of nanometers to a few micrometers. Modeling the ablation process helps engineers design low-damage laser processes (e.g. to separate wafers or for OLED displays) faster and identify the physical effects on which the ablation process is based. Model for simulating the ablation dynamics In order to identify the underlying physical processes, engi- neers at Fraunhofer ILT and RWTH have developed a model that depicts the optical, thermal and mechanical properties of the thin films during and after irradiation with ultrashort laser pulses. The free electron density within the material changes drastically due to ionization as it is irradiated with intense ultrashort laser pulses. As a result, the optical properties of the material change during the laser pulse. By determining the induced energy, the institutes were able to model the resulting heating and thermal expansion within the thin films. Since the optical properties change during the laser pulse, the amount of energy introduced into the material could be determined and the resulting heating and thermal expansion in the material modeled. Identification of the ablation mechanisms This model can be used to predict the temperature and me- chanical stress distributions in the material. If the mechanical stresses exceed a threshold value specific to a material, the ablation process is mechanically dominated. Similarly, an abla- tion criterion can be defined for thermally dominated ablation when the melting or evaporation temperature is reached. The ablation criteria are fulfilled for the areas marked in red in the illustrations above. The basic considerations of this work were carried out as part of a DFG project at the Instruction and Research Department for Nonlinear Dynamics of Laser Manufacturing Processes (NLD) of RWTH Aachen University under the funding code 423531130. Author: Dorian Kürschner M. Sc., dorian.kuerschner@nld.rwth-aachen.de Contact Dr Martin Adams Group Manager Computational Methods Phone +49 241 8906-509 martin.adams@ilt.fraunhofer.de 31

Contact Dr Christian Vedder Head of Department Phone +49 241 8906-378 christian.vedder@ilt.fraunhofer.de Surface Technology and Ablation Department Micro and Nano Structuring Thin Film Processing Polishing In-Volume-Structuring and Lithography 33 33

MultiFlex – Multi-beam processing of non-periodic structures 1 1 x 8 beam array. 2 MultiFlex system at Fraunhofer ILT. Laser material processing with ultrashort pulse (USP) lasers is an excellent method for processing almost any material precisely and melt-free. It enables ablation with virtually no thermal influence. This makes USP laser processing attractive for many industrial applications, including toolmaking. A major disadvantage is the long process time compared to ablation using nanosecond laser radiation, for example. A common method of compensating for this disadvantage is processing with several sub-beams, known as multi-beam processing. The classic variant is limited to periodic structures, as the individual sub-beams are used to perform parallel processing with a fixed spatial distance. MultiFlex removes this restriction. Individually modulated sub-beams for multi-beam processing To circumvent the process’ limitation to periodic structures, each sub-beam is guided by a separate acousto-optical modulator (AOM). With this, the sub-beam pulse can either be deflected precisely into a beam dump or passed through to the scanner, i.e. switched off or on. The individual AOMs are controlled and synchronized with the laser beam source via an FPGA module developed for this purpose. This allows a beam matrix consisting of 8 x 8 sub-beams, for example, to be moved over the workpiece in a similar way to a dot matrix printer, where- by only the sub-beams that are needed for processing at the respective point are switched on. This switching pattern for the AOMs must be calculated beforehand in software developed for this purpose. All sub-components are installed in a laser material processing system typical for the industry. Scaling by means of non-periodic multi-beam processing The use of MultiFlex technology for non-periodic multi-beam machining with 64 individually modulated sub-beams enables an increase in productivity by a factor of around 30 compared to single-beam machining. The exact factor depends on the geometry to be machined. The work was carried out as part of the EU MultiFlex project under the funding code 825201. Author: Marcel Kniffler M. Sc., marcel.kniffler@ilt.fraunhofer.de Contact Dr Dennis Haasler Group Manager Micro and Nano Structuring Phone +49 241 8906-8321 dennis.haasler@ilt.fraunhofer.de 35

Laser-based production of high-performance non-stick coatings 1 Anti-adhesive coating on a CFRP roller Lightweight rollers made of CFRP are increasingly being used as replacements for conventional rollers made of steel or alu- minum in industrial applications. Since they weigh less, energy consumption in the application can be minimized and the service life of rollers, motors and bearings effectively increased. Functional coatings are often required for these lightweight rollers in order to improve the performance of the surfaces. Common high-performance anti-adhesive coatings are based either on sol-gel systems or high-performance polymers such as PEEK (polyether ether ketone), but these materials must be thermally post-treated after being applied to the CFRP rollers. This process step requires temperatures between 200 and 400 °C, which are above the damage limit of the CFRP rollers (approx. 120 °C). Owing to this limitation, the desired anti-adhesive properties cannot be achieved with conventional oven-based processes, as the component would have to be brought to too high a functionalization temperature. Combination of high-performance anti-adhesive coatings and CFRP rollers Fraunhofer ILT has developed a laser process that enables sol-gel and PEEK-based high-performance coatings to be deposited on temperature-sensitive CFRP rollers. The applica- tion-specific materials developed by Rhenotherm Kunststoffbe- schichtungs GmbH are sprayed onto the rollers and dried in a first step. Thermal functionalization is carried out by means of a diode, whereby a defined surface temperature is achieved via pyrometric temperature measurement with closed-loop control of the laser power. Since the local and temporal resolution of the energy input is so high, the necessary functionalization temperatures in the anti-adhesive coating can be achieved for a short time without causing thermal damage to the substrate. Energy savings thanks to lightweight CFRP rollers Such coated lightweight rollers can be used in production systems in the manufacture of hygiene articles, the packaging industry and the automotive industry and, thanks to their low weight, contribute to energy savings in industrial processes. The R&D project underlying this report was carried out on behalf of the Federal Ministry for Economic Affairs and Climate Action under the funding code 03LB3051B. Author: Samuel Fink M. Sc, samuel.fink@ilt.fraunhofer.de Contact Samuel Moritz Fink M Sc Group Manager Thin Film Processing Phone +49 241 8906-624 samuel.fink@ilt.fraunhofer.de 37

AI-based, automated determination of the process parameters for laser polishing 1 Industrial 3D laser polishing system. 2 In-situ white light interferometry measurement. As with many laser processes, determining suitable process parameters for laser polishing of metals requires expert knowledge and a great deal of manpower. When materials are exchanged and there are major changes in the initial rough- ness, the process parameters must be adapted experimentally or redetermined. The surface structures created during laser polishing, such as undercuts, bulges or martensite needles, limit the minimum achievable roughness. However, the surface structures can be significantly reduced by specifically adjust- ing the process parameters. To do this, the test surfaces are first polished with the laser. Then, process experts carry out topography measurements using white light interferometry and analyze these for surface structures, a process step that involves considerable effort. Classification of surface structures with AI The automated laser polishing system already saves up to 50 percent working time compared to conventional process parameter development. For the first time, an AI module for classifying surface structures was trained on a data set of over 2500 topography images. Previous results show an accuracy of over 95 percent for individual structure recognition and up to 82 percent for structure overlays. The R&D project "3+2 AI La-Pol" underlying this report was carried out on behalf of the Federal Ministry of Education and Research under the funding code 01DM21003B. Author: Sven Linden M. Sc., sven.linden@ilt.fraunhofer.de Self-learning, automated laser polishing system To automate the development of process parameters, Fraunhofer ILT has integrated a white light interferometer into a laser polishing system, in collaboration with Karl H. Arnold Maschinenfabrik GmbH & Co. Newly developed control soft- ware (work flow controller) coordinates the laser polishing system, laser and optics as well as the white light interfero- meter, thus enabling an automated process consisting of experiment planning, laser polishing and subsequent in-situ measurement. Measured topography images are checked for roughness features and as are surface structures using AI-supported analysis software. With the help of a module specially developed for laser polishing metals, process parame- ters are evaluated and provided to the user in pre-filtered form. Contact Dr. Edgar Willenborg Group Manager Polishing Phone +49 241 8906-213 edgar.willenborg@ilt.fraunhofer.de 39

Laser Medical Technology and Biophotonics Fraunhofer ILT‘s interdisciplinary team uses biological, clinical and laser expertise to develop laser-based solu- tions for medical applications and biomedical research Our research portfolio covers high-precision laser surgi- cal systems, devices for in vitro diagnostics and environ- mental analysis, as well as innovative stereolithographic methods and bioprinting processes In the field of laser surgery, our team focuses on processes and systems for cutting hard tissue in minimally invasive procedures in neurosurgery. In addition, we develop diagnostic processes based on microfluidic sorting and detection systems for the differentiation and separation of pathogens as well as diagnostic particles for infection diagnostics. We offer customers in bio- medical research innovative laser processes for the targeted transfer of single cells onto diagnostic chips. We also have patented stereolithographic processes that allow the automated production of individualized medical devices. Contact Dr Achim Lenenbach Head of Department Phone +49 241 8906-124 achim.lenenbach@ilt.fraunhofer.de Laser Medical Technology and Biophotonics Department Laser Medical Technology and Bioanalytics Biofabrication 41 41

5 mm OCT-monitored laser osteotomy for microsurgical procedures 1 Laser cut on compact bovine bone. 2 OCT residual thickness measurement on thin bone lamellae. Laser systems for safe osteotomies OCT measurements on bone tissue Cutting and removing bone tissue during surgical procedures is currently carried out using mechanical tools such as drills, milling cutters or chisels. The accuracy, automation and patient safety of these instruments are severely limited, especially when bone has to be removed near critical structures. Laser-based osteotomy, on the other hand, promises constant cutting speeds at increased precision and improved cosmetic results. When an optical measuring process is integrated into the cutting process, laser ablation can also be monitored and controlled online, thereby improving patient safety. The laser process can also be combined with a robotic system. Real-time residual thickness measurement for automated control of the laser cutting process A compact applicator is used to focus the radiation from the cutting laser onto the bone surface. The laser applicator can be guided over the surgical area using a motorized positioning system, a robotic arm or manually. With optical coherence tomography (OCT) – an interferometric measurement process – the residual thickness of the bone can be measured in real time, whereby the measurement beam in the laser applicator is superimposed coaxially to the cutting laser beam. In addition to measuring the residual thickness inline, the process can generate a 3D surface profile of the kerf and adapt the local ablation rate to inhomogeneities in the bone. Within the STELLA project, Fraunhofer ILT has developed an OCT sensor with a central wavelength of 835 nm and a measurement frequency of up to 80 kHz. This sensor can be used to measure a maximum residual bone thickness of up to 400 μm on compact bone tissue. The laser applicator was used to successfully record 3D surface profiles of laser-generated incision joints on the skull bone of a sheep. Surgeons who perform cranial, spinal as well as oral and maxillofacial surgery can make great use of a laser osteotome with interferometric process monitoring. The project is funded by the Fraunhofer-Gesellschaft as part of the ATTRACT research program. Author: Christina Giesen M. Sc., christina.giesen@ilt.fraunhofer.de Contact Dr Georg Meineke Group Manager Laser Medical Technology and Bioanalytics Phone +49 241 8906-8084 georg.meineke@ilt.fraunhofer.de 43

Isolation of B cells using laser-based cell printing 1 Microreaction vessels. 2 System for cell insulation. State of the art and application Successful material transfer for cell analysis When patients fall ill with a virus such as SARS-CoV-2, the body’s immune system responds and forms pathogen-specific receptors on its own immune cells (B cells). The presence of such a receptor provides information about the immune status of the affected patients after infection or vaccination. To provide rapid information on immunization in the population during an epidemic, large patient cohorts need to be screened using time-consuming and cost-intensive procedures. For this reason, the BMBF project "B-Cell-Immune" aims to develop a miniatu- rized process chain that enables laboratories to rapidly analyze several 100,000 samples in microvessels. Process chain and solution The project partner LPKF Laser & Electronics SE provides microreaction vessels with a diameter of 200 to 400 μm. Filling these vessels efficiently in a needle-based approach is still an unsolved problem today. Fraunhofer ILT is, therefore, develop- ing a laser-based process that enables users to both filling microreaction vessels with cell culture medium at a rate of up to 1 kHz and separate B cells from a patient sample into these vessels. The samples are then analyzed by the clinical partners at Hannover Medical School. Fraunhofer ILT has shown that microreaction vessels in glass with a diameter of up to 200 μm can be reliably filled with cell culture medium without contaminating the neighboring vessels. This material template forms the basis for the subsequent iso- lation of individual cells in the microreaction vessels. For this purpose, the institute uses laser-induced forward transfer (LIFT) with a MIR laser beam source of emission wavelength λ = 2.94 μm to vaporize water and trigger a microjet. This microdispensing process can print at rates of up to 1 kHz without contact and without needles. The partners have demonstrated that single cells can be transferred into microreaction vessels and are carrying over the process for use with B cells. The joint project "B-Cell-Immune" underlying this report was carried out on behalf of the Federal Ministry of Education and Research under the grant number 13GW0590D. Author: Richard Lensing M. Sc., richard.lensing@ilt.fraunhofer.de. Contact Dr Nadine Nottrodt Group Manager Biofabrication Phone +49 241 8906-605 nadine.nottrodt@ilt.fraunhofer.de 45

Joining and Cutting The Fraunhofer ILT laser experts in the Joining and Cutting Department investigate a wide field of laser material processing. The applications they examine use a large variety of materials, from metal and plastic to wood and glass, and address a wide range of workpiece dimensions, from thick sheets to thin foils The department focuses on laser-based connection techno- logy – in particular, for electrical contacts in energy storage and power electronics – including laser welding and soldering as well as processes such as plastic welding and glass frit bonding. For laser cutting, it develops processes and process- specific components such as optics, cutting nozzles and control systems. In addition to high-performance processes such as high-speed cutting and thick sheet cutting, the experts look at integrating applications that combine cutting, welding and additive powder processes. The application areas here range from battery technology and fuel cell manufacturing to packaging and textile technology. We offer users customized solutions from feasibility studies to complete individual laser processing machines. Contact Dr. Alexander Olowinsky Head of Department Phone +49 241 8906-491 alexander.olowinsky@ilt.fraunhofer.de Joining and Cutting Department Joining of Metals Joining of Plastics and Transparent Materials Cutting 47 47

Double-beam welding of metallic bipolar plates Hydrogen is regarded as the energy source of the future. The core of the so-called PEM (polymer electrolyte membrane) fuel cell is the bipolar plate, responsible for important tasks such as media distribution and supply, including hydrogen as the reaction medium. The metallic bipolar plate is suitable for mobile applications due to its lower weight. It consists of two formed metallic foils that have to be joined together, which means both quality and cycle times have to fulfill stringent requirements. Laser welding is suitable for this application as its process speed is so high. However, from a welding speed of 500 mm/s (30 m/min), the first signs of humping appear. Humping is a seam defect that manifests itself in the form of periodic melt accumulations on the seam surface, which impair the seam quality and severely limit the process speed. Two laser beams on one workpiece With a single-mode fiber laser emitting in the NIR (1070 nm) range, high-quality seams can be produced at a process speed of 30 m/min. One approach to reducing the production cycle time while maintaining this seam quality is to link two process- ing heads. Two AxialScanFiber30 scanners from RAYLASE are used for this setup. Two lasers, each with a maximum output power of 1000 W, are also used. Both laser beams can be switched on simultaneously. 1 Setup with two RAYLASE AS-Fiber 30 scanners. 2 Welding a bipolar plate. Reduction of the cycle time The processing time for a typical welding contour for a bipolar plate is approx. 4.6 seconds when only one processing beam is used. In contrast, the processing time with double-beam welding is only approx. 2.4 seconds, a reduction of approx. 48 percent. A further advantage – the two beams can be used on one spot in the overlapping area of the two scan fields, which helps researchers investigate methods to prevent humping. Author: Elie Haddad M. Sc., elie.haddad@ilt.fraunhofer.de Contact Dr André Häusler Group Manager Joining of Metals Phone +49 241 8906-640 andre.haeusler@ilt.fraunhofer.de 49

Compressed glass feedthroughs for temperature-sensitive components Laser-based manufactured compressed glass feedthroughs for LTCC. When hermetic encapsulations are designed, compressed glass feedthroughs are often used as a contacting interface between the sensor unit and the evaluation electronics since they can withstand high temperatures, high pressure and aggressive media. These feedthroughs consist of a metal outer part (mount), a sintered glass body and usually metallic inner conductors. Traditionally, they are manufactured in a furnace process lasting several hours, in which all components are heated to the melting temperature (> 400 °C) of the glass. The furnace process is unproblematic for metallic conductors. However, a furnace process is unsuitable if the conductors are replaced by a multilayer ceramic made of low temperature co-fired ceramics (LTCC) with integrated structures and tem- perature-sensitive elements. A manufacturing process is then required in which the thermal load is minimized and the critical thermal destruction threshold of the individual components is not exceeded. Laser instead of furnace Unlike a furnace, the laser applies energy locally so that the temperature load for temperature-sensitive components can be reduced and damage avoided. The radiation emitted by the laser is focused on the metal mount. The radiation energy absorbed by the mount is converted into thermal energy, which leads to a rapid rise in temperature. Part of the heat is conducted into the glass body, which wets both the mount and the LTCC ceramic as soon as the melting temperature of the glass is reached. In this way, pressure-resistant and helium- tight connections are created. (Pressure resistance > 800 bar, leakage rate in the range of 10-9 to 10-10 mbar*l/s). Local energy input reduces thermal load Investigations have shown that the LTCC ceramic is subjec- ted to the greatest thermal stress by the laser process in the wetting area. Temperatures equal to the melting temperature of the glass body are reached here. As the distance increases in the longitudinal direction, the temperature of the ceramic drops to below 100 °C. The functionality of temperature-sensi- tive components is maintained there. The work was funded by the Federal Ministry for Economic Affairs and Climate Action on the basis of a resolution passed by the German Bundestag. Author: Dipl.-Ing. Heidrun Kind, heidrun.kind@ilt.fraunhofer.de Contact Maximilian Brosda M. Eng. Group Manager Joining of Plastics and Transparent Materials Phone +49 241 8906-208 maximilian.brosda@ilt.fraunhofer.de 51

Process monitoring for laser blanking and laser welding with AI 1 Laser blanking demonstrator system DIPOOL. Cutting blanks for automotive production with laser radiation from coil material, known as laser blanking, is a very efficient and flexible method of production – compared to conventional punching – while also saving resources. This is partly because waste is reduced and nesting in continuous production is very flexible. Continuous processes need to be extremely reliable, in particular, since an undetected cut and the associated system downtime are more costly to rectify than ejecting individual faulty parts from individual circuit boards. This also applies to other roll-based applications, such as the production of bipolar plates or battery electrodes. Monitoring with an AI-based analysis of the process signals helps to identify process limits at an early stage and reduce safety reserves, thereby increasing the productivity of the machines. Intelligent laser machines In a demonstrator laser blanking system, which is being set up at the DIPOOL project partner Dreher, Fraunhofer ILT used AI to evaluate the process status in real time based on a time series analysis of photodiode signals. Of the various machine learning methods tested, convolutional neural networks (CNN) show the best results for this application. With a process computer with FPGA, the cycle time for data acquisition, pre-processing and inference is 1 to 2 milliseconds and is, therefore, sufficiently fast for the high-speed cutting process. A perfect duo: AI and MILM Minimally invasive laser modulation (MILM) is crucial for high data quality, which makes reliable inference possible in the first place, and leads to characteristic, easily interpretable response signals, which can also be used to ensure that a brief crossing of the separation limit is detected. Fraunhofer ILT is pursu- ing an analogous objective in laser beam welding to detect process deviations and weld seam irregularities. To increase the information content in this application, the institute records the process data multispectrally within the DIPOOL project and uses it to detect the weld penetration limit. The joint project DIPOOL is funded by the Federal Ministry of Education and Research as part of the ProLern funding measure (reference 02P20A000) and supervised by the Project Management Agency Karlsruhe (PTKA). Author: Gerald Kolter M. Sc., gerald.kolter@ilt.fraunhofer.de Contact Dr Frank Schneider Group Manager Cutting Phone +49 241 8906-426 frank.schneider@ilt.fraunhofer.de 53

Contact Dr Thomas Schopphoven Head of Department Phone +49 241 8906-8107 thomas.schopphoven@ilt.fraunhofer.de Laser Material Deposition Department Additive Manufacturing and Repair LMD Coating LMD and Heat Treatment 55 55

Additive manufacturing of a rocket nozzle for space travel 1 Thin-walled cooling channel samples. 2 CAD model of the demonstrator to be manu- factured, © ArianeGroup. Not only does the space industry have to fulfill political climate protection requirements, it is also under increasing pressure to lower costs as international competition grows. To ensure Europe remains competitive, ArianeGroup and 17 other part- ners are cooperating in an EU project to develop cost-effective and climate-neutral space components for the next generation of rockets. Fraunhofer ILT is involved in the process develop- ment and construction of a full-scale rocket nozzle demons- trator in the meter range using laser material deposition (LMD). When thrust nozzles for launch vehicles are conventionally manufactured, multi-stage process steps and processing sta- tions are used, which are not only expensive, but also require a great deal of time. The project partners aim to significantly reduce these by means of additive manufacturing using LMD. Scalable installation spaces thanks to LMD technology As part of the process development, Fraunhofer ILT investiga- ted various path planning strategies for creating the required cooling channel structures. In the following steps, the institute will continue to develop the findings by building ever larger segments and sample bodies to validate the manufacturing process and the material properties. After successful validation, a production demonstrator with the corresponding dimensions of the real components will be built up. The large and flexibly scalable installation space of LMD technology enables such large components to be additively manufactured efficiently. Construction of cooling ducts with thin walls When the process parameters were being developed, the hot gas wall was designed with thin walls so that efficient cooling of the thrust nozzle can be ensured. The partners are investi- gating and continuing to develop various parameters and cons- truction strategies for the different wall thicknesses needed for an efficient nozzle wall with cooling channel structure in order to produce larger nozzle structure. The ongoing ENLIGHTEN project is funded by the European Health and Digital Executive Agency HADEA as part of the EU program HORIZON-CL4-2021-SPACE-01-21 (https://project-enlighten.eu/). Author: Dipl.-Ing. Jochen Kittel, jochen.kittel@ilt.fraunhofer.de Contact Min-Uh Ko M Sc Group Manager Additive Manufacturing and Repair LMD Phone +49 241 8906-8441 min-uh.ko@ilt.fraunhofer.de 57

Production of lead-free plain bearing layers using EHLA 1 Plate segment with CuSn10 layer. 2 CuSn10 EHLA process. In mechanical engineering, plain bearings are among the most frequently used bearing types. Their functional surfaces are usually separated from each other by a thin film of oil. Common materials for the sliding layers are bronze or white metal alloys, such as those used for piston drums in high-performance axial piston pumps. Here, lead bronze is cast oversized onto the relevant surfaces of the steel base bodies in an energy-intensive process. Since the scaled component needs to be reworked, there is a considerable loss of raw material. Lead is also highly harmful to health and is subject to restrictions in accordance with EU Regulation 2015/628 (REACH). The industry is there- fore striving to replace lead bronze with lead-free plain bearing materials and to sustainably redesign the entire production process chain. Along with the companies ADMOS Gleitlager and Rosswag GmbH, Fraunhofer ILT is developing an energy- efficient production process chain to apply lead-free sliding material with extreme high-speed laser material deposition (EHLA) using the example of piston drums. graphically and carried out hardness measurements. On the basis of selected parameter sets, samples are produced and tested for the bond strength tests according to Chalmers. EHLA layers with higher adhesive strength The CuSn10 alloy can be used to produce firmly adhering, crack-free and virtually pore-free coatings. The test results show that EHLA coatings made of CuSn10 have a bond strength that is around 37 % (375 MPa) higher than that of conventionally cast plain bearing layers. The R&D project KMU-ERBE under- lying this report is being carried out on behalf of the Federal Ministry of Education and Research in cooperation with the DLR project management organization under the funding code 01LY2109A. Author: Dipl.-Ing. Stefanie Linnenbrink, stefanie.linnenbrink@ilt.fraunhofer.de Advantages of using EHLA EHLA is particularly advantageous for this application as it is an economical, environmentally friendly and resource-saving process for the production of fused metallurgically bonded coatings. As part of the project, different lead-free bronze alloys are atomized into powder material and processed using EHLA. By varying the process parameters, Fraunhofer ILT welded layers onto C45R plates, analyzed them metallo- Contact Viktor Glushych M Sc Group Manager Coating LMD and Heat Treatment Phone +49 241 8906-152 viktor.glushych@ilt.fraunhofer.de 59

Laser Powder Bed Fusion The scientists in the Laser Powder Bed Fusion (LPBF) Department develop innovative solutions for indus- trial 3D printing The technology they cover ranges from process control and systems engineering to the qualification of LPBF for the additive series production of functional components made of metal- and polymer- based high-performance materials In process and system technology, our research focuses on implementing control and monitoring solutions for com- ponent- and application-adapted LPBF process control as well as developing customer-specific machine components and overall systems for additive manufacturing. In application development, the team transfers innovative additive manu- facturing technologies to industrial production and covers topics ranging from production-oriented design to function and sensor integration in components all the way to life cycle analysis for additive manufacturing chains. The department’s broad technology portfolio is rounded off by laser-based manufacturing solutions for polymers, which are being re- searched in cooperation with the FH Aachen – University of Applied Sciences. Contact Dr Tim Lantzsch Head of Department Phone +49 241 8906-193 tim.lantzsch@ilt.fraunhofer.de Laser Powder Bed Fusion Department LPBF Process and Systems Engineering LPBF Application Development AM Polymers 61 61

All-electric concept aircraft powered by fuel cells, © Airbus Group. Laser powder bed fusion for the sustainable aviation of tomorrow How can aviation be made greener? This is shown by the first results As the climate crisis worsens, the aviation sector is increasingly coming under the spotlight when it comes to reducing CO2 emissions. As part of the aviation research program of the Federal Ministry of Economics and Climate Protection, the TIRIKA research initiative is addressing this issue. It is mainly focusing on developing materials and technologies necessary to make emission-free flight possible. The use of hydrogen as an energy source is a promising approach, but it places con- siderable strain on the components used, loads that can impair their durability, safety and functionality. The additive manu- facturing process laser powder bed fusion (LPBF) can be used to process high-performance materials that can withstand hydrogen-rich environments. The initiative also intends to exploit the great geometric design freedom and the possibility of functional integration with LPBF. The Fraunhofer ILT approach Two TIRIKA work packages are being worked on in parallel at Fraunhofer ILT. In one, the institute is investigating the LPBF process for novel, high-strength aluminum alloys for use in hydrogen-rich environments. In the other, it is looking closely at sensor-based approaches for detecting component defects during the ongoing LPBF process. In this way, the functionality of the manufactured components can be ensured, and the effort of the usually lengthy and cost-intensive downstream quality control reduced by using LPBF process monitoring data. At Fraunhofer ILT, the LPBF process was qualified for process- ing the two high-strength aluminum alloys Custalloy and Scancromal®. A relative component density of 99.5 percent was achieved at a build-up rate of more than 100 cm³/h. Investigations into the mechanical properties of both materials and a heat treatment route will follow. The process sensors used detect defects relative to quality (e.g. inclusions of foreign particles with sizes of up to 400 μm) both in the powder bed and in the melting process. Author: Luke Schüller M. Sc., luke.schueller@ilt.fraunhofer.de Contact Niklas Prätzsch M Sc Group Manager LPBF Process and Systems Engineering Phone +49 241 8906-8174 niklas.prätzsch@ilt.fraunhofer.de 63

Ecologically sustainable aviation through additive manufacturing Exposure of an inlet guide vane (IGV) in the LPBF process. In the mobility sector, commercial aviation contributes sig- nificantly to greenhouse gas emissions. Since there are few alternatives to this form of transportation, especially on long and intercontinental routes, industry and research are focusing their efforts on making air transport more sustainable. The development and spread of new technologies such as Additive Manufacturing (AM) can make a decisive contribution to this: These processes are characterized by high resource efficiency combined with high weight savings through topology opti- mization. In this context, the Laser Powder Bed Fusion department at Fraunhofer ILT is participating in the EU research program "Clean Sky 2," which aims to significantly reduce the ecolo- gical impact of aviation on our habitat. Development of models for the ecological assessment of additive manufacturing Life Cycle Assessment is used to evaluate the ecological impact of AM processes. Fraunhofer ILT used ecological analyses to initially record the material and energy flows required in component production for the necessary sub-processes, e.g. the laser powder bed fusion process. Together with partners, Fraunhofer ILT recorded primary data for the Life Cycle Inven- tory (LCI) at machine level during production. This data was then used to create models of the process chains, from the raw material production to the recycling of the component. Using the models developed, the project partners were able to identify and substitute relevant emitters with sustainable alternatives. Assessment of the ecological footprint for additively manufactured aerospace components Fraunhofer ILT set up and evaluated the ecological analyses for several applications and materials. Thanks to AM’s high degree of freedom in production, high recycling rate of the powder material and weight savings, the institute’s analyses show that additive manufacturing has a smaller ecological footprint than conventional production routes, despite the high energy con- sumption during production. Particularly in repair applications, additive manufacturing processes constitute an ecologically sustainable alternative to conventional processes. Author: Christian Weiß M. Sc., christian.weiss@ilt.fraunhofer.de 65

WIR!-Bündnis LASER.region.AACHEN 1 Meeting of the alliance partners at FH Aachen. What is the Bündnis LASER.region.AACHEN? The WIR!-Bündnis LASER.region.AACHEN is an alliance funded by the Federal Ministry of Education and Research to promote structural change in Europe‘s largest lignite mining region. The production and use of new laser-based production solutions will create sustainable jobs and economic success for the LASER.region.AACHEN. The WIR!-Bündnis LASER.region. AACHEN brings together numerous fields of knowledge, sec- tors and technologies. More than 50 industrial partners from all areas of laser technology, Fraunhofer ILT, RWTH Aachen University and FH Aachen cooperate as research institutions as well as educational, funding and social partners to offer optimal conditions for this transformative change. different laser-based processes and seek solutions for improved data-based linking to develop a continuous digital laser-based process chain. The “Accessible laser material processing through explainable artificial intelligence (ZuLeKi)” project involves testing AI approaches for laser material processing that enable non-specialized experts to use AI in SMEs, e.g. to use machine status data and process data for quality assurance of laser-based processes. The aim of the “Advanced optical elements for adapted beam shaping (FortOP)” project is to harness new, innovative optical components for adapted laser beam shaping. In particular, easily integrated concepts for laser material processing are a focus of this project. The WIR!-Bündnis LASER.region.AACHEN is an alliance project funded by the Federal Ministry of Education and Research. Which innovation projects are being carried out as part of the alliance? In the LASER.region.AACHEN alliance, the partners create and develop new processes and products, joint technology platforms, service concepts and new training and continuing education concepts within various projects. In the "Strategy development" project, the partners define and translate stra- tegic goals of the alliance into a strategy. Research topics for joint projects are defined in workshops and meetings between research and industry partners. In the “Combined laser pro- cesses (KoLa)” project, they systematically detect interfaces for Contact Prof Sebastian Bremen Group Manager AM Polymers Phone +49 241 8906-537 sebastian.bremen@ilt.fraunhofer.de 67

Contact Dipl-Ing Hans-Dieter Hoffmann Head of Department Phone +49 241 8906-206 hansdieter.hoffmann@ilt.fraunhofer.de Lasers and Optical Systems Department Optics Design and Diode Lasers Solid State Lasers Fiber Lasers EUV Technology Packaging Ultrafast Lasers NLO and Tunable Lasers 69 69

Data chain for the digital production of individualized optics 1 Two-lens unit designed with partial automation. 2 Surface measurement of a blank after pressing. Optical systems and applications are topics that cross many markets, from cameras and LIDAR sensors for autonomous driving to satellite-based systems to measure greenhouse gases. The core components of optical assemblies are precisely manufactured lenses, which are increasingly characterized by progressive individualization, more complex geometries and ever shorter product development cycles. Traditional subtractive manufacturing technologies, such as grinding and polishing, are quickly reaching their limits as technology and scaling advance. The production and delivery times for customized optics are often several weeks to months. Laser-based optics production Together with Fraunhofer IPT and IST, Fraunhofer ILT is deve- loping a digitalized and laser-based production chain. The aim of the PREPARE project OPTICS48 is to produce individualized optical systems within 48 hours. The basis for the production chain is formed by blanks that can be produced cost-effectively in large quantities using glass molding. Customized optics are manufactured from these blanks with the laser-based shaping and modifying by ablation, polishing and precision shape correction. Thanks to the digital control of the laser processes, each individual system can be customized without incurring additional costs. Subsequently, an anti-reflective coating is applied, so that the new production chain can cover the entire added value of a glass optical element. Semi-automated design of an achromatic two-lens unit In a first step, Fraunhofer ILT linked the semi-automated optical design of an aspherical, achromatic two-lens unit and the digital shadow of the described production chain via a web server. Based on the focal length and the wavelength pair to be corrected, the achromatic lens is calculated from N-BK7 and P-SF69 blanks. The ablation time of the shaping process was then minimized while complying with the imaging quality requirements. With a web server user interface, all data required for the production and coating process can be downloaded, such as the angular distribution of the incoming and outgoing radiation. For continuous production tracking, the measurements taken during production will be linked to the achromatic lens via an upload. Author: Lucas Warnecke M. Sc., lucas.warnecke@ilt.fraunhofer.de Contact Dr Martin Traub Group Manager Optics Design and Diode Lasers Phone +49 241 8906-342 martin.traub@ilt.fraunhofer.de 71

Frequency-converted fiber amplifier for atmospheric research 1 Laboratory demonstrator of the frequency-converted fiber laser. Nitrogen oxides play an important role in atmospheric chemistry and their measurement provides important findings for air quality and for understanding climate change, among other things. The Institute of Energy and Climate Research at the Forschungszentrum Jülich is investigating tropospheric photo- chemistry using state-of-the-art physical measurement techno- logy. For laser-induced fluorescence measurement of nitrogen oxides in the atmosphere, Fraunhofer ILT will develop and build an appropriate beam source by evaluating, adapting and improving an existing laser design. Subsequently, Fraunhofer ILT will set up a laboratory demonstrator by combining a fiber amplifier with a frequency conversion unit, which generates the required pulsed laser radiation with peak powers of > 1.5 W and with a wavelength of 215 nm in the deep ultraviolet. Laser concept The laboratory demonstrator consists of a polarized, three- stage fiber amplifier with a linewidth of < 10 MHz and a three- stage frequency conversion to convert the infrared wavelength to the deep ultraviolet. The fiber amplifier is seeded with a DFB diode at 1074 nm; the diode is pre-amplified with an electrically pulsed semiconductor amplifier to generate the 2 to 3 ns long pulses and then post-amplified in a core-pumped, regenerative fiber amplifier and two cladding-pumped linear fiber amplifiers. The individual amplifier stages are separated from each other by Faraday isolators. The required output wavelength is achieved with a subsequent frequency conversion unit, consisting of a frequency doubling from 1074 nm to 537 nm and two-stage sum frequency generation over 358 nm to 215 nm. Results By adapting and optimizing the fiber amplifier design, Fraunhofer ILT was able to demonstrate all target parameters. Furthermore, the peak power in the infrared was tripled and thus the peak power in the deep ultraviolet was increased disproportionately to > 6.5 W. The laboratory demonstrator was delivered to Forschungszentrum Jülich and can be used there for experimental studies in the future. This work was funded by the BMBF as part of the FONA strategy "Research for Sustainability" in the project "ACTRIS-D: National Facilities." Author: Dipl.-Phys. Martin Giesberts, martin.giesberts@ilt.fraunhofer.de Contact Patrick Baer M Sc Group Manager Fiber Lasers Phone +49 241 8906-8251 patrick.baer@ilt.fraunhofer.de 73

Highly efficient UV laser for daylight-capable atmospheric LIDAR 1 Diode-pumped alexandrite laser emitting in the UV in laboratory setup. Since the impact of anthropogenic emissions on the climate is increasing, it has become ever more important to better understand and monitor atmospheric processes. The Leibniz Institute of Atmospheric Physics (IAP) concentrates on measur- ing wind and temperature profiles of the atmosphere up to an altitude of 120 km. Mobile resonance LIDAR systems are mainly used for this purpose. Combining several such systems with overlapping observation areas creates a network with unrivaled resolution and area coverage. The data acquired is sometimes collected continuously over long periods of time under difficult environmental conditions, such as in polar or tropical regions, or in remote locations. LIDAR systems must therefore not only be robust, compact and easy to transport, but also work autonomously and require low-maintenance. When adapted wavelengths in the UV range are used, mea- surements can be conducted under daylight conditions without reduced resolution caused by the solar background. Implementation in LIDAR system for measurement campaign The laser achieves an average power of 1.5 W at 500 Hz in the UV with a very high electro-optical efficiency of 2 percent. The line width is extremely narrow-banded due to seeding and cavity length control in order to scan the resonance line. Two prototypes will be built, integrated into two LIDAR systems and tested with measurements across Europe. Since the alexandrite laser is tunable, additional resonance wavelengths in the UV can also be addressed with little effort, which means that the altitude range can be extended even further and the effects of space weather on the atmosphere can be measured directly. The work is being carried out as part of the EU project EULIAA under the funding code 101086317. Author: Sarah Scheuer M. Eng., sarah.scheuer@ilt.fraunhofer.de Concept for efficient frequency conversion Using a diode-pumped alexandrite laser that has already been tested in compact LIDAR systems, Fraunhofer ILT developed a concept that continues to meet the high spectral requirements. By efficiently doubling the frequency, the institute was able to achieve the target wavelength in the UV, the iron resonance at 386 nm, and demonstrated that it is suitable as a LIDAR emitter. Contact Dr. Bernd Jungbluth Group Manager NLO and Tunable Lasers Phone +49 241 8906-414 bernd.jungbluth@ilt.fraunhofer.de 75

Pockels cell for space missions 1 Integrated Pockels cell for space missions. If laser systems are to be used in space, e. g. LIDAR for atmospheric research, the optomechanical components these systems contain, such as Pockels cells, must be stable, both mechanically and thermally. Since the BBO crystal has such special mechanical properties, it is difficult to build a Pockels cell. Not only does the assembly of the crystal pose a challenge, but so does its need to withstand thermal loads of -30 °C to +50 °C and mechanical loads of up to 20 Grms. Furthermore, the assembly should be carried out without organic substances. For these reasons, Fraunhofer ILT is using a soldering techno- logy it developed to assemble a Pockels cell. but also analyzed the internal stress of the crystal, and mea- sured capacitance and inductance. All test criteria were met during this series of tests. In the environmental tests, the posi- tion deviation was below the required 100 µrad. Finally, the Pockels cell was subjected to an overvoltage test with 5 kV direct current and a long-term test with 6.21 GShots. No damage was detected on the overall assembly, especially on the crystal. After successful qualification, the Pockels cell was installed in the MERLIN EQM system. The Pockels cell con- cept can be used for high-performance applications or when laser systems are used in harsh environmental conditions. Setup of the Pockels cell The BBO crystal was soldered into a ceramic housing with special steel grid structures. A soft solder was used to reduce the mechanical stresses in the crystal. Furthermore, the stresses were reduced by the geometrical structure of the soldered connection. The ceramic housing was then soldered onto a holder and adjusted using the pick & align process in the laser system. Pockels cell concept successfully implemented The entire assembly, consisting of the Pockels cell and holder, has undergone an extensive qualification program. The Fraunhofer ILT not only carried out electro-optical tests, The work is funded by the BMWi under FC 50EP1601 and is being carried out on behalf of the German Aerospace Center (DLR) as a subcontractor of Airbus Defence and Space GmbH. Author: Witalij Wirz M. Eng., witalij.wirz@ilt.fraunhofer.de Contact Dr Heinrich Faidel Group Manager Packaging Phone +49 241 8906-592 heinrich.faidel@ilt.fraunhofer.de 77

Non planar ring oscillator at 2 μm wavelength Third-generation gravitational wave detectors (GWD) have enormous potential to help scientists make new discoveries in astrophysics or cosmology. They require, however, highly stable laser systems in all parameters. In current laser systems for GWDs, non planar ring oscillators (NPRO) with an emission wavelength of 1064 nm are often used as seed lasers for a subsequent amplifier chain. As part of the Interreg project E-TEST, Fraunhofer ILT is developing an NPRO laser emitting at a wavelength of 2 μm, which serves as a highly stable seed laser for a power-stabilized fiber amplifier system. This wave- length can be used to extend the range of gravitational wave measurements in the lower frequency spectrum. Monolithic laser with maximum stability An NPRO is a monolithic laser oscillator in which the laser beam propagates in a ring using total internal reflection through the laser crystal. This field-tested system enables very high power and frequency stability. In order to achieve a wave- length of 2 μm, Fraunhofer ILT developed and built an NPRO based on an Ho:YAG laser medium. This is pumped through a multi-stage, highly stable thulium fiber laser developed at Fraunhofer ILT. Little heat is generated in the NPRO laser crystal thanks to the small wavelength difference between the two laser media. 1 Laboratory demonstrator of a 2 μm NPRO. Results and outlook Two different NPRO systems have been built. The institute demonstrated that the first system reached an output power of up to 350 mW at a wavelength of 2120 nm in longitudinal single mode, and the second system up to 50 mW at a wave- length of 2090 nm. In both systems, an almost diffraction- limited beam quality was achieved, and both a relative power stability of 0.2 percent and a degree of polarization > 20 dB were demonstrated. The next step will be to amplify the NPRO at 2090 nm using a holmium fiber amplifier chain developed at Fraunhofer ILT. This system is to be frequency- and power- stabilized using active methods in order to meet the extreme requirements of future gravitational wave detectors. The work was funded by the European Regional Development Fund on behalf of the Ministry of Economic Affairs, Industry, Climate Action and Energy of the State of North Rhine-Westphalia. Author: Johannes Ebert M. Sc., johannes.ebert@ilt.fraunhofer.de Contact Dipl-Phys Marco Höfer Group Manager Solid State Lasers Phone +49 241 8906-128 marco.hoefer@ilt.fraunhofer.de 79

Networks and Clusters Fraunhofer Networks The Fraunhofer ILT together with other Fraunhofer Institutes bundles its competencies in clusters and lighthouse projects and develops applications for industry and research Founded in 1949, the Fraunhofer-Gesellschaft currently operates 76 institutes and research units with nearly 32,000 employees, predomi- nantly scientists and engineers. In the annual business volume of 3.4 billion euros a good 3.0 billion euros stem from contract research, which is based on three funding pillars: industry projects and license-fee revenue sum up to 836 million euros. Another share of contract research revenue comes from publicly funded research projects. The final share is base funding that is supplied by the German federal and state governments and enables our institutes to develop solutions now that will become relevant to the private sector and society in a few years. The high proportion of industrial revenue is Fraunhofer‘s unique sell- ing point in the German research landscape. Highly motivated employees are the most important factor in Fraunhofer’s success. The research organization therefore creates opportunities for independent, creative and goal-driven work. Fraunhofer fosters profes- sional and personal development in order to provide career opportunities for its employees in the private sector and society at large. The Fraunhofer-Gesellschaft is a recognized nonprofit named after the Munich scholar Joseph von Fraunhofer (1787–1826), who enjoyed equal success as a scientist, inventor and entrepreneur. The Fraunhofer-Gesellschaft The Fraunhofer-Gesellschaft, based in Ger- many, is one of the world’s leading applied research organizations. It plays a crucial role in the innovation process by prioritizing research in key future technologies and transferring its research findings to industry in order to strengthen Germany as an economic hub as well as for the benefit of society. Fraunhofer is an attractive and established party for public- private partnerships. As an important customer group, small- and medium-sized companies tap into Fraunhofer‘s expertise and resources to maintain their competitiveness by developing new tech- nologies. Here Fraunhofer experts support industry partners from ideation to market launch. Fraunhofer is one of the most active patent applicants in Germany and Europe. The organization is developing an extensive, inter- national patent portfolio in various technology sectors, primarily as a basis for transferring technology through research projects, spin- offs and licensing. Examples include techno- logies for the energy transition, cybersecurity and underlying models for generative artificial intelligence. This contribution to strengthening Germany as a hub for innovation and ensuring its viability in the future helps to create jobs in Germany, boost investment effects in the pri- vate sector and increase the social acceptance of new technology. Collaboration projects with excellent research partners and companies across the globe ensure that the Fraunhofer- Gesellschaft remains in direct contact with the most prominent scientific communities and economic areas. At a glance 76 institutes 32,000 employees Business volume of 3.4 billion euros 3.0 billion euros of which designated as contract research Figures as of: April 2024 81

Zukunftsmarkt Quantentechnologien Networks and Clusters As head of the expert commission on laser inertial confinement fusion appointed by the BMBF, Prof. Constantin Häfner hands over the memorandum to Federal Research Minister Bettina Stark-Watzinger on May 22, 2023, © BMBF / Hans-Joachim Rickel. in this field of technology. Federal Minister Bettina Stark-Watzinger set up a high-caliber, international commission of experts, which I was appointed to chair. The first meeting took place almost at the same time as the NIF experiment. We presented the minister with a comprehensive memorandum back in May 2023. It contains general recommendations and many proposals for the expansion of fusion research, the necessary infrastructure and cooperation between science and indus- try. The speed and public commitment send a strong signal; politicians have recognized the potential of inertial confinement fusion. In September 2023, it followed up with action. The German government is investing € 1 billion in fusion research over the next five years and is aiming to rapidly industrialize fusion technology. As director of Fraunhofer ILT, how do you see this development in strategic terms? Nuclear fusion is a great opportunity for Germany as a high-tech location. We have many market leaders here in the field of lasers and photonics who can contribute to the success of laser inertial confinement fusion. In addition, technological developments for fusion can be transferred to other applications. The age of the laser is young. We cannot even imagine what it can and will achieve in the future. The announced competition-based funding is an excellent prospect for the indus- try: Together we can develop technologies for fusion. Openness to technology is the guiding principle here. Fraunhofer acts as an enabler and bridge builder whose broad spectrum of expertise makes a decisive contribution to the development of key technologies, be it in target and material development, measure- ment technology or the implementation of AI and machine learning, in sustainable photonic production processes for power plant compo- nents or the development of lasers and optics at Fraunhofer ILT. Over 30 Fraunhofer Institutes have expertise in the field of fusion. At our Fraunhofer Focus Day “Nuclear Fusion,” we decided to create a comprehensive compe- tence matrix and to intensify the transfer from science to industry. To this end, Fraunhofer ILT has set up a fusion technology task force, which is fully committed to this and strategi- cally coordinates the topic. It is so powerful that the motto must be: “All hands on deck!“ We are also building and expanding bilateral partnerships internationally. The task now is to maintain the rapid pace and bring talent on board. To do this, Germany must build and maintain excellent research facilities that train the minds of tomorrow. "Energy is the fuel of our modern society. Fusion has the potential to revolutionize our energy supply...." Bettina Stark-Watzinger Contact Prof. Constantin Haefner Director Phone +49 241 8906-110 constantin.haefner@ ilt.fraunhofer.de 83

Networks and Clusters Innovation Cluster at the Aachen Location In Aachen, Fraunhofer ILT has been operating innovation clusters for many years, ensuring close local interaction between industry and science in the field of photonics. Cooperation on site Industry cooperation at the Aachen site Innovation clusters not only enable the transfer of know-how, but also promote young talent and encourage spin-offs. The advantage of a single location makes both personnel and infrastructural networking much simpler. For example, Fraunhofer ILT – thanks to its constantly updated infrastructure – has one of the largest laser system parks in Europe. Its proximity to RWTH Aachen Uni- versity, in turn, guarantees the institute has an influx of very well-trained engineers and scientists. Systematic and long-term coope- ration between the university, Fraunhofer ILT and industry takes place, in particular, at the Research Campus Digital Photonic Production (DPP). Spin-offs are also generated from this environment, continuing the long spin-off tra- dition of Fraunhofer ILT with over 40 spin-offs in 30 years. www.forschungscampus-dpp.de Innovation clusters as a source of transferring know-how, promoting young talent and founding spin-offs. On the laser industry side, numerous medium- sized companies have joined forces to form LASER.region.Aachen. The consortium intends to position the Aachen region as a center for agile laser-based production solutions, thereby creating sustainable jobs. www.laserregionaachen.de On the laser user side, companies at the Aachen site are also bundling some of their relevant research activities together. For example, the Fraunhofer Institutes for Produc- tion Technology IPT and Laser Technology ILT as well as the Machine Tool Laboratory WZL and the Chair for Digital Additive Production DAP at RWTH Aachen University, together with 19 industrial partners, established the International Center for Turbomachinery Manufacturing - ICTM in 2015. The network‘s industrial partners include large and medium- sized companies from the fields of turboma- chinery, automation and machining techno- logy, and additive manufacturing, among others. The center focuses on research and development for the manufacture and repair of turbomachinery components, which is covered by the partners in all areas. www.ictm-aachen.com 8585

Chair for Technology of Optical Systems TOS Instruction and Research Depart- ment for Nonlinear Dynamics of Laser Manufacturing Processes NLD By establishing the Chair for Technology of Optical Systems in 2004, RWTH Aachen accor- ded recognition to the increasingly central role of highly developed optical systems in manufacturing, the IT industries and the life sciences. Research activities focus on the development and integration of optical com- ponents and systems for laser beam sources and laser devices. Highly corrected focusing systems for a high laser output, beam homogenization facilities and innovative beam shaping systems are all key components of laser systems used in pro- duction engineering. These include adaptive optics and free-form optics for innovative beam shaping for process adapted intensity distributions. The chair develops micro and macro-optical components for high-power diode lasers and combines them to form systems. It also investigates lithography and material analysis with resolutions smaller than 50 nanometers in the field of EUV technology. Prof. Carlo Holly (Director of the chair) www.tos.rwth-aachen.de Founded in 2005, the Instruction and Research Department for Nonlinear Dynamics of Laser Manufacturing Processes NLD explores the basic principles of optical technology, with emphasis on modeling and simulation in the fields of application macro welding and cutting, additive manufacturing, precision processing with ultrafast lasers and PDT in dentistry and dermatology. Mathematical, physical and experimental methods are being applied and enhanced to investigate technical systems. The application of mathematical models is helping to achieve a better understanding of dynamic interrela- tionships and to create new process engineer- ing concepts. The results of these analyses are made available to industrial partners in the form of practical applications in collaboration with the Fraunhofer Institute for Laser Techno- logy ILT. The main educational objective is to teach a scientific, methodological approach to modeling on the basis of practical examples. Prof. Wolfgang Schulz (Head of the department) www.nld.rwth-aachen.de Networks and Clusters Main building and "SuperC" of the RWTH Aachen University, © RWTH Aachen University / Peter Winandy. 87

Research Center DPP Industry Building DPP To shorten innovation cycles, different research areas need to network in an inter- and transdisciplinary manner. Scientists from different institutes and chairs at RWTH Aachen University conduct research together on different topics with common goals over a relatively long period of time. The Research Center DPP, which opened in 2019 and was fully operational in 2020, offers researchers space for fundamental research in the field of photonics on approximately 4,300 square meters of floor space – including 2,800 square meters of laboratories, clean rooms and halls. The institutes and chairs currently involved come from six faculties at RWTH Aachen University: Mechanical Engineering, Mathematics, Computer and Natural Sciences, Electrical Engineering and Information Techno- logy, Georesources and Materials Engineering, Medicine and Economics. Companies can set up shop in the Industry Building Digital Photonic Production – which is in the immediate vicinity of the Fraunhofer Institute for Laser Technology ILT – to deve- lop new components, systems, processes, process chains or business models in the field of optical technologies, especially for production technology. The Industry Building DPP thus offers the necessary infrastructure for long-term, strategic cooperation within the framework of the Research Campus DPP. Premises such as laboratories and offices can be rented as needed through the private operator. Mixed teams from industry and science can interact and inspire each other in open space structures and jointly occupied laboratories. Education and training as well as access to scientific events on site are also very efficient and future-oriented since com- panies "enroll" at RWTH Aachen University. 1 Industry Building DPP (right) and Research Center DPP (left) in the photonics cluster, © Research Campus DPP, Aachen. 2 Entrance area of the Industry Building DPP in the Photonics Cluster, © Research Campus DPP, Aachen. Contact Dr. Christian Hinke Phone +49 241 80-40418 christian.hinke@llt.rwth-aachen.de Prof. Constantin Haefner Phone +49 241 8906-110 constantin.haefner@ llt.rwth-aachen.de wwwforschungscampus-dppde 89

Networks and Clusters Customer References Customer references The companies listed here are a representative cross-section of Fraunhofer ILT‘s extensive customer list. Status December 2023. Printed with the kind permission of our partners. 91

Networks and Clusters Location Initiatives – Battery and Hydrogen Lab The energy transition requires sustainable energy from photovoltaics and wind power, for which energy storage systems such as batteries and green hydrogen are needed For this purpose, Fraunhofer ILT has established the Battery Lab and the Hydrogen Lab at its Aachen location Hydrogen Lab – the future belongs to green hydrogen Hydrogen is a versatile energy carrier that requires a great deal of energy for its produc- tion, but has a number of advantages over batteries: Green hydrogen can be stored for a long time and can use the existing natural gas infrastructure. It can be used to power many industrial processes that currently still use natural gas, oil or coal. In the future, hydrogen-powered peak-load power plants will ensure that power supply remains secure by feeding electricity back into the grid. But sustainable hydrogen is still too expensive, and we need a lot of it. By constructing its own hydrogen laboratory, the Hydrogen Lab, Fraunhofer ILT has created the best possible framework for perfecting the fuel cell as the heart of hydrogen technology – from the basics to series production. Fraunhofer scientists are conducting research in various projects to drive forward the cost- optimized and demand-oriented series pro- duction of fuel cells. They help industry and society tap the technological and economic potential of this technology and accelerate its structured rollout. On 300 square meters, the Hydrogen Lab offers a wide range of laser test facilities for different dimensions and designs. The facilities cover the laser-related manufacturing steps along the process chain for the production of metallic bipolar plates used in fuel cells. From the laser-based production of forming tools and surface functionalization to cutting and welding, individual processes can be examined in the lab as well as interrelation- ships and interactions in the process chain. Users can test the laser-produced components for their hydrogen tightness and efficiency with the existing test benches. The Hydrogen Lab‘s wide range of technical equipment opens up a variety of possibilities for seamless interdisciplinary collaboration. For public projects and industry cooperation, it offers a unique space to achieve synergy effects at the highest scientific and techno- logical level. »The bundling of relevant system technology in the Hydrogen Lab accelerates development.« Dr. Alexander Olowinsky Contact Dr. Alexander Olowinsky Head of Department Joining and Cutting Phone +49 241 8906-491 alexander.olowinsky@ ilt.fraunhofer.de 93

Internationally networked Fraunhofer and QuTech get the quantum internet off the ground With foreign companies and branches of German companies abroad, Fraunhofer ILT carries out bilateral as well as joint projects. In addition, Fraunhofer ILT participates in major international projects, such as in climate research with the Franco-German space mis- sion MERLIN or in the design of research pro- grams, such as with the European Commission via the technology platform Photonics21. Fraunhofer ILT also coordinates advisory bodies for ministries on internationally relevant topics such as nuclear fusion research and enters into strategic partnerships such as with the Lawrence Livermore National Laboratory LLNL in California, USA. The institute‘s staff accompanies its international developments by being involved in selected associations and networks such as the European Photonic Industry Consortium EPIC at the European level or OPTICA and the Laser Institute of America LIA at the transatlantic level. In a long-term partnership, the Fraunhofer- Gesellschaft and QuTech – a collaboration of the TU Delft and the Netherlands Organiza- tion for Applied Scientific Research TNO – are working together on the development of the quantum internet gateway. Within this frame- work, the Ministry of Economic Affairs, Indus- try, Climate Action and Energy of the State of North Rhine-Westphalia is funding a quantum internet node in Aachen, which is being set up by Fraunhofer ILT in close cooperation with QuTech and will be used to test photonic system solutions. www.ilt.fraunhofer.de/en/technology-focus/ quantum-technology.html Quantum Internet Alliance Adopting a multidisciplinary approach, the Quantum Internet Alliance brings together expertise from industry, research and educa- tion from nine different European countries. Thanks to initial successful developments, the network intends to make a global quantum internet made in Europe a reality. Fraunhofer ILT is actively contributing its photonic exper- tise to the network. www.quantuminternetalliance.org Opening speech from Dr. Lutz Aschke at the Photonics21 general meeting in April 2023 in Brussels, © Photonics21 / Iris Haidau (Babylonia). Contact Dipl.-Phys. Axel Bauer Phone +49 241 89806-194 axel.bauer@ilt.fraunhofer.de 95

Training the Next Generation 1 Participants of the mechanical engineering student university. 2 Prospective female researchers at the Fraunhofer Science Campus WiCa in Aachen. Working at Fraunhofer ILT www.ilt.fraunhofer.de/en/ Headline, 9 pt jobs-and-career.html Titel Vorname Name Geschäftsbereich XXX Tel. +49 12 3456-XXXX Fax +49 12 3456-XXXX Mobil +49 12 3456-XXXX vorname.name@ fraunhofer.de 97 a metal sheet with their names. Finally, they could take home a "mouse made of metal powder" as a souvenir. Fraunhofer Science Campus WiCa November 29 to 30, 2023 in Aachen bonding company contact fair November 8, 2023 Under the motto "Bonding at RWTH Aachen University. A fast track to your dream job!" Fraunhofer IPT and ILT presented themselves at a joint stand at the recruiting fair to provide students and graduates from the engineering, economics and natural sciences in particular with comprehensive information about entry- level and career opportunities. Particularly noteworthy was the keen interest shown by female STEM students, who were invited to the Fraunhofer Science Campus on site to promote young female talent. Graduate Congress Cologne November 23 to 24, 2023 Fraunhofer ILT was represented at the joint Fraunhofer stand and provided graduates with comprehensive information about master's and doctorate degrees as well as the Fraun- hofer Science Campus. A total of 38 STEM students and graduates accepted the invitation from Fraunhofer Aachen to find out about the exciting research fields and career opportunities at the Aachen site. They were given a look behind the scenes at Aachen's Fraunhofer Institutes ILT, IPT and IME and discussed ideas for the research of tomorrow. Strategies for sustainable value creation in industrial production were deve- loped in a workshop. Other highlights of the event included individual tours of the institute, a professional career session, job speed dating and numerous personal discussions with the Aachen researchers. RWTH Digital Career Day for women December 5, 2023 At the end of the year, 30 female students and doctoral candidates at RWTH Aachen University had the opportunity to find out about potential employers online at the "Digital Career Day." Two female scientists from the Lasers and Optical Systems depart- ment presented Fraunhofer ILT in a company pitch. In the subsequent Q&A session in a small group, personal questions were answered, insights into everyday working life given and the various entry opportunities presented.

Events and Publications Fairs Fraunhofer ILT is regularly represented with current research topics at trade fairs in Germany and abroad All departments of Fraunhofer ILT take part in the leading trade fair LASER World of PHOTONICS in Munich January 28 to February 2, 2023, San Francisco, USA SPIE Photonics West June 14 to 16, 2023, Munich ees Europe Fraunhofer ILT was represented at the joint stand of the Federal Republic of Germany. There were also 18 presentations by experts from Fraunhofer ILT and RWTH Aachen University at the conference accompanying the trade fair. April 17 to 21, 2023, Hanover Hannover Messe At the joint Fraunhofer booth at the Hannover Messe 2023, Fraunhofer ILT presented laser technologies for battery cell production and, for the first time, the new combination process Simultaneous Machining and Coating (SMaC) developed at Fraunhofer ILT. April 19 to 21, 2023, Yokohama, Japan OPIE‘23 For the first time, Fraunhofer ILT was represented as a co- exhibitor at the joint stand of the Federal Republic of Germany at the OPTICS & PHOTONICS International Exhibition in Yokohama. The optics design and diode lasers group as well as the polishing group were able to impress visitors to the international trade fair with their comprehensive expertise. May 23 to 25, 2023, Stuttgart The Battery Show Europe Fraunhofer ILT presented exhibits on the topics of "Direct laser sintering of solid electrolyte and mixed cathode layer on steel" and "Continuous roll-to-roll electrode production" at the joint Fraunhofer booth of the Battery Alliance. At Europe's largest international trade fair for batteries and energy storage systems, Fraunhofer ILT, represented by the Joining of Metals and Micro Joining groups, demonstrated various innovative laser applications for electromobility and energy research. June 27 to 30, 2023, Munich LASER World of PHOTONICS & LASER World of QUANTUM Fraunhofer ILT presented its R&D at the joint Fraunhofer booths and impressed visitors with highlights such as the LIDAR systems developed at the institute and their application for industry and climate research. In addition, Fraunhofer ILT and the associated LLT and TOS chairs at RWTH Aachen University were involved in numerous forums and panels at the World of PHOTONICS Congress. November 7 to 10, 2023, Frankfurt am Main formnext Fraunhofer ILT presented current innovations in the fields of laser powder bed fusion, laser cladding, thin-film processes for LPBF and laser polishing of metals and plastics at the joint Fraunhofer stand. November 13 to 16, 2023, Düsseldorf COMPAMED At COMPAMED, Fraunhofer ILT presented its R&D at the IVAM joint stand and showed exhibits from the fields of laser medical technology and bioanalytics as well as joining of plastics and transparent materials. 99

1 2 November 23 to 24, 2023 AI for Laser Technology Conference AI in laser technology opens up new oppor- tunities and is driving progress in various sectors. At the 3rd AI for Laser Technology Conference, around 60 experts from research and industry learned more about the driving development of AI in today's industry. Contri- butions on topics such as new methods and algorithms for process control, image and data analysis as well as adaptive processes for self- learning machines and measurement techno- logy were a recurring theme throughout the event. 1 Presentation by Dr. André Häusler at the LSE'23. 2 Well attended: 7th UKP work- shop at "DAS LIEBIG" in Aachen. 3 Participants of the EUV Source Workshop 2023 at the Technology Center Aachen. control were presented, which were developed as part of the REVaMP project to characterize the input materials and to optimize the melting processes. October 21 to 25, 2023 EUV Source Workshop 2023 For the first time, Aachen welcomed the international community of EUV suppliers and end users to the Technology Center Aachen for the EUV Source Workshop 2023. Fraunhofer ILT and the Chair for Technology of Optical Systems TOS at RWTH Aachen University were pleased to support the annual workshop of EUV Litho, Inc. and EUV-IUCC with on-site organization as well as presentations, posters and showcases. The workshop provided a forum for researchers, suppliers and end users in the field of EUV and X-ray light sources to present their work and discuss a wide range of potential applications. As part of the work- shop, Sophia Schröder from the TOS chair was able to impress with her poster presentation and win the Poster Session Award. 3 101

Events and Publications Patents Patents Germany Patents Europe DE 10 2022 110 651 Kompaktes optisches Spektrometer DE 10 2022 204 685 Optik, Vorrichtung und Verfahren zur Bearbeitung eines Werkstücks DE 10 2022 101 043 Verfahren und Einrichtung zur Reduzierung der Auswirkungen thermischer Linseneffekte bei der Lasermaterialbearbeitung DE 10 2021 108 009 B4 Multi-Wellenlängen UV-Strahlungsquelle sowie UV-Sonde, insbesondere für die Fluoreszenzanalyse DE 10 2019 207 421 Verfahren und Vorrichtung zum Glätten einer Oberfläche eines Bauteils durch Bearbeitung mit energetischer Strahlung DE 10 2019 202 222 Ablenkspiegel aus Diamant sowie Verfahren zur Herstellung DE 10 2016 209 065 Verfahren und Vorrichtung zur Prozessüberwachung bei der generativen Fertigung von Bauteilen DE 10 2008 032 532 Verfahren und Vorrichtung zum präparierenden Lasermaterialabtrag 50 2021 001 3428 Anlage und Verfahren zur teil- oder vollautomatisierten Demontage von Geräten 50 2020 004 5173 Verfahren zum Bohren oder Schneiden durch Abtragen von schmelzfähigem oder verdampfungsfähigem Material eines Werkstücks 50 2020 006 0423 Verfahren zur Terminierung optischer Strahlung sowie dafür ausgebildete optische Strahlfalle 50 2017 014 3520 Verfahren und Vorrichtung zur Bearbeitung einer Werkstoffschicht mit energetischer Strahlung EP 3858717 Anlage und Verfahren zur teil- oder vollautomatisierten Demontage von Geräten EP 3986661 Verfahren zum Bohren oder Schneiden durch Abtragen von schmelzfähigem oder verdampfungsfähigem Material eines Werkstücks EP 4031319 Werkstoffzuführungsvorrichtung EP 3953099 Verfahren zur Terminierung optischer Strahlung sowie dafür ausgebildete optische Strahlfalle EP 3615680 Verfahren und Vorrichtung zur Bereitstellung einer eine gewünschte Zielprotein-Expression aufweisenden Zelllinie EP 3538349 Verfahren und Vorrichtung zur Bearbeitung einer Werk- stoffschicht mit energetischer Strahlung Patents USA US 11 845 376 Radar- und Lichtausstrahlungsanordnung für Fahrzeuge zum Ausstrahlen von Licht und Radarstrahlung sowie Ver- fahren und Verwendung Scientific publications and lectures You will find a list of Fraunhofer ILT’s scientific publications and lectures as well as bachelor and master theses online in our media center on the Internet at: wwwiltfraunhoferde/en/media-centerhtml 103

Funding Bodies Some joint projects presented in this annual report have been supported with public funding We would like to express our gratitude to the public donors for thier support at this point 105105