A hub for technological sovereignty
In a new research building, the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena will conduct research on the nanometer (nm)-scale structuring of photonic components using electron beam lithography. Potential applications include high-performance chips for AI, microelectronics, and quantum computing, as well as high-precision measuring instruments for Earth observation and space exploration. On the roof of the new building, the institute is also commissioning a ground station for satellite-based quantum communication. In this interview, researchers Dr. Falk Eilenberger and Dr. Matthias Goy from Fraunhofer IOF discuss the new technological approaches and their potential.
Dr. Eilenberger and Dr. Goy, you will now be conducting your research in a modern new building at Fraunhofer IOF. What are your first impressions?
Dr. Falk Eilenberger: Great! From a scientific perspective: a lot of high-quality space for setting up large-scale scientific equipment and conducting experiments. In the new building—which is already the third expansion on our campus—we can expand our existing research across more than 2,000 square meters and tackle new strategic topics derived from the high-tech agenda. Highlights include the new electron beam lithography system in the significantly expanded cleanroom and the ground station for satellite communications. Thanks to the striking telescopic dome on the roof, this is naturally the most visible new addition on campus. But in day-to-day operations, the laboratories, cleanrooms, and new office spaces in the immediate vicinity of the main building will prove just as valuable to us. We’re hearing a lot of very positive feedback from our community—and we ourselves are truly excited about the new possibilities!
Dr. Matthias Goy: Many guests seeing the building and the ground station for the first time are visibly impressed. It’s now up to us to make the most of these new opportunities—whether it’s Falk’s group in electron beam lithography or my team in the field of laser and quantum communication.
Could you briefly outline your technological approaches?
Eilenberger: Electron beam lithography is part of a broader technological chain, but it is a central step in that process. Whether for the fabrication of large optical components with extreme precision or for the production of photonic chips. Electron beam lithography is also required for the production of high-precision measuring instruments.
Goy: Satellite-based quantum communication is a security-relevant topic. We have been developing methods in quantum communication for some time now to enable practically eavesdrop-proof communication in the future. This requires quantum key distribution that is both fast and reliable.
And we could achieve this in the future using satellites, provided there are suitable ground stations with photon sources for generating single photons, with detectors for their reception, and methods for virtually loss-free coupling into fiber-optic networks. We will use our ground station to further develop this quantum key distribution.
Eilenberger: I’d like to add something briefly.
Of course!
Eilenberger: A new building like this isn’t something you just throw together. Rather, it requires intensive strategic planning and precise design to ensure the right issues are addressed in the long term. The relevance of quantum communication could hardly be higher in terms of IT security, and with electron beam lithography, we are operating in a strategically important field to make Europe more independent in the production of microchips and to strengthen local manufacturing chains—whether for space exploration, fusion, or security issues.
Many use cases that we are addressing in the new building planned years ago are reflected in the German government’s current high-tech agenda.
Let’s talk about your research. What does the new electron beam lithography system do?
Eilenberger: It applies extremely precise structures to substrates. To put into perspective just how precise these optical gratings are, a change of scale helps. If you were to enlarge such a grating to the size of Thuringia, it would look something like a very flat potato field with very straight furrows. The furrows would be spaced exactly 30 cm apart, with a maximum horizontal and vertical tolerance of 2 cm. So, when scaled to the size of Thuringia, the difference between the lowest and highest points would be just two centimeters. When we structure substrates, we’re dealing with resolutions in the range of 20 nanometers (nm) and low single-digit nm tolerances.
With our new system, we can achieve twice the precision over 60 percent more area than before. It will carry us well into the second quarter of this century and enable us to manufacture even larger and more precise optics.
Can you briefly explain the process?
Eilenberger: The technology has its roots in the semiconductor industry; we adapt its processes and, in part, its materials to realize optical systems. At first glance, they seem rather unspectacular. To the human eye, they are glass plates shimmering with rainbow colors. This shimmer stems from the nano-grating structures on the surface. They break down the incident white light into its spectral components. This is because the structures in the glass are roughly as fine as the wavelengths of light. With precisely defined and highly accurate gratings on the glass wafer, specific optical systems can be implemented for astronomy, Earth observation, and climate research, as well as for lasers, process control, or future fusion power plants. Manufacturers of photonic chips—so-called Photonic Integrated Circuits (PICs)—or of EUV systems for the microchip industry also require such optics.
Until now, we were able to manufacture them in sizes up to nine inches (~400 cm²). With the new system, the area is nearly 1000 cm², with structures that are half the size and twice as precise. This is the prerequisite for much more precise measuring instruments and lasers with significantly higher energy.
What is the difference from EUV patterning, for the development of which the Fraunhofer IOF received the German Future Prize together with Trumpf and ZEISS?
Eilenberger: EUV patterning is a replication technology. It copies predefined structures billions of times onto wafers. This requires so-called master structures as a template or mask. These master structures are produced using electron beam lithography. This method is therefore much more flexible but also much slower than EUV patterning.
Both processes create nanometer-scale structures, but as a research institute, we need a process that is as flexible as possible so that we can offer tailor-made solutions for every research project, every customer, and every industrial contract.
What’s the story with Earth observation instruments?
Eilenberger: Basically, it’s about the spectral splitting of light. Here in Jena, we develop large mirrors, large free-form optics, and sometimes even entire instruments, some of which are used for Earth observation. This involves spectrometers for atmospheric research and metrology, aimed at better understanding climate and weather phenomena.
This brings us to the satellites with which you will communicate optically from your ground station in the future. What’s the story behind this?
Goy: Inside the dome mentioned earlier—which is visible from far away—there is a telescope with a laboratory located below it. This is where we are continuing our research in the field of quantum communication, and we will be focusing primarily on quantum key distribution. Essentially, this involves systems used here on the ground. This ranges from generating single photons using the appropriate photon sources to developing detectors capable of detecting these single photons so they can be further processed. We develop all of this on a component-by-component basis with a specific focus on space applications—for example, to equip satellites with single-photon sources. That would be a prerequisite for satellite links to enable the global deployment of quantum key distribution. This requires ground-based optical stations like ours. Until now, there was only one station in Germany capable of establishing optical links to satellites. We are now the second ground station capable of doing this.
So you’re still pretty much at the beginning of this research?
Goy: Yes, that’s correct. We’re now working on solutions for precise PAT—Pointing, Acquisition, and Tracking: You have to locate the satellite and, during the acquisition phase, ensure that the satellite can see the ground station and vice versa. And tracking involves following its orbit, since it’s moving at high speed. It’s a major and important field of research because the faster and more precise the PAT process is, the more effectively the satellite link time can be utilized. That’s essential for commercialization. But the challenges continue on the ground. We must guide the light captured by the telescope into an optical fiber with as little loss as possible in order to ultimately distribute the signals to the ground-based fiber-optic network. This entails the highest possible demands on fiber coupling. Especially since the light signals must first pass through the Earth’s atmosphere, causing wavefront distortions that we must compensate for using adaptive optics. Losses must be minimized along the entire path from the satellite to the fiber. This is where our research comes in. Despite all the disruptive influences from sunlight, thermals, and turbulence, we must succeed in distributing quantum keys around the clock.
What approaches are there?
Goy: In addition to adaptive optics, we need very high-quality optical filters to detect the individual photons amidst all the stray light. To achieve this, we at the institute are working with industry to develop high-performance optical coatings. As I mentioned, we’re dealing with individual photons. Current sources can generate more than a million photon pairs per second. When we receive them from the satellite, we have to process them just as quickly. This, in turn, places high demands on detection. In the BMFTR-funded QuNET initiative, we have gained a great deal of insight into ground-based free-space and fiber-based quantum networks, which we now want to apply to satellite-based quantum communication. We are now taking the technology to the next level: space.
There is a global race to develop quantum communication via satellites. Who is currently in the lead?
Goy: Other nations demonstrated several years ago that satellite-based quantum communication is feasible. Europe is just getting started here. But commercial competition is only one aspect of this. Quantum communication is a central component of national security strategies. We must therefore develop this technology in Germany and Europe and build our own expertise. Because it is a matter of resilience. We must be able to ward off cyber threats while maintaining technological sovereignty. This requires us to forge our own path in research.