WORLDS OF GLASS

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The view into the endless expanses of the universe

BY ANJA FAHS

The history of astronomy has been experiencing a regular construction boom for several years. In Chile, on Hawaii or in outer space, telescopes are being built that make all the facilities constructed to date look tiny. For instance, the largest optical telescope in the world – the European Extremely Large Telescope, or E-ELT for short – is currently being built on Cerro Armazones, a mountain in Chile. With a main mirror 39 metres in diameter, this will be the largest telescope in the world, providing insights into the universe that have been impossible until now. Its photographs will have 16 times the resolution of those taken by the famous Hubble space telescope.

For this ambitious goal, the oversized telescope relies on a five-mirror design: a large main mirror (M1), and four smaller mirrors (M2 to M5) as reflectors. All of the orders for mirror substrates awarded to date within the scope of the E-ELT project are being filled by the international technology group Schott. Headquartered in Mainz, Germany, the company is one of the world’s largest producers of technical glasses and glass ceramics. It has been providing larger dimensioned telescope mirror substrates since 1903, and since 1970 the material Schott Zerodur® has claimed its place as the de facto standard. Substrate for the segmented M4 mirror of the E-ELT left the company’s plant in Mainz last year. This was followed by another order for Zerodur® glass ceramics as part of the project.
We spoke with Christoph Fark, Executive Vice President in the advanced optics department at Schott, about the company’s participation in the E-ELT project and how the innovations at Schott will change our daily lives in future.

I’ve read that you are the last remaining glass maker in the Western world.
That is not quite correct. There are other glass manufacturers besides us in the Western world, but we are the only company producing optical glass.

You were awarded the order to manufacture mirror substrates for the largest telescope in the world, the primary mirror of which measures nearly 40 metres in size. How can we envision a telescope with these dimensions?
We are delighted that the European Southern Observatory (‘ESO’) recently awarded us the contract to produce the secondary mirror M2 and the tertiary mirror M3 for the European Extremely Large Telescope, or E-ELT for short, each with a diameter of four metres. We already delivered discs made of Zerodur for the adaptive M4 mirror last year; these are further processed to create mirror segments that are just 1.95 millimetres thin. The order for the M1 main mirror, measuring 39 metres in diameter and composed of 798 hexagonal mirror segments with a diameter of 1.4 metres each, has not yet been awarded.
But back to your question: the E-ELT will be the largest space telescope in the world. The mega-telescope is being built on Mount Cerro Armazones in Chile and is scheduled to go into operation in 2024. This is a very complex optical system that collects light from outer space and uses numerous mirrors to direct this light to high-tech analytical equipment. Our competence in this highly demanding project is focused on the mirror substrates. The mirror substrates are manufactured using Zerodur, a material that has proven its performance for decades and is characterised by near-zero thermal expansion. This means that the material barely expands at all in the event of temperature change. Even if fluctuations in temperature are slight in these telescopes’ locations, this characteristic is important to the effort of capturing images from outer space in top quality and free of distortions.

How do mirrors function as reflectors in a telescope?
To put it simply: the mirrors collect and focus light from space, which in some cases has been travelling for billions of years, and uses multiple mirrors to channel it into the analytical systems. So it is concentrated, as it were, before it is interpreted. This results in high-resolution images of distant stars and galaxies. And thanks to our extremely dimensionally stable glass ceramics, these images are impressively clear and free of noise.

What exactly is Zerodur, and what are the benefits that make this product so important for the telescope?
It is a special kind of glass ceramic that is extremely insensitive to fluctuations in temperature. Whether exceptionally hot or cold, the characteristics of the material do not change. That is the advantage. People who use this material don’t have to worry about surprises. This creates planning and research security, including in astronomy applications such as the E-ELT, which cannot tolerate even the slightest compromises.

What are the other areas in which this product is used?
In microlithography or in the field of precision measuring technology, for example. But in the kitchen, too, albeit in a slightly modified form. In terms of the qualities of the material used, Ceran glass ceramic cooktops are closely related to Zerodur and put the benefits of this material to use in everyday life.

What did this order for the E-ELT mean for your company? How can you serve the sustained high demand for your glass ceramics?
We are very proud of the orders we’ve had to date within the framework of the E-ELT project. To continue to meet the sustained high demand for Zerodur in future, we invested heavily in the location this year. A second melting furnace has been in operation for several months, offering us great flexibility and significantly higher production capacity. We are also investing in brand-new CNC machines for the finishing of our product. All things considered, we have devoted an amount in the double-digit millions; thanks to the latest technology, we are already well positioned to meet the growing demand.

Schott Advanced Optics teams up with international research and competence centres. What are the areas in which research is currently ongoing?
The areas are diverse, and the list of our research partners is long. One current project is investigating ultra-thin glass, which is wound on a roll. In this research project, which is funded by the German Federal Ministry of Education and Research (BMBF), we are partnering with the Fraunhofer Institute, the industrial-equipment company Von Ardenne and the polymer and laminating expert tesa SE. The cooperation is extremely productive and promising.

Where do you see the greatest need for innovation? Which industries have an urgent need for new developments?
If you take a look at the smartphone market, in recent years you have seen a steady evolution, a real revolution. Innovative pressure on industry sectors is mounting, and there is repeated discussion of flexible displays. Flexible or even foldable displays need dependable protection. Glass is the material of choice for this. Sensors are also a major topic in general, and not just in smartphones. There are numerous fields of application for ultra-thin glass here, for example as wafer-thin cover glass for so-called biosensors.

So are further developments for glass occurring particularly in the area of mobile end devices?
Innovations are firmly anchored in our corporate DNA. To be successful in the long term, a technology company like Schott has to continuously open new doors. And that includes the market for consumer electronics. Here, glass performs not only externally as a cover glass for displays, camera modules or fingerprint sensors, but also in more concealed areas, e.g. as a filter glass in nearly all high-resolution optics.
Glass is an essential component when it comes to future innovations in mobile devices. The dimensions are diverse, starting with design. Flexible or curved displays need to be protected, and that’s where glass comes into play. For instance, the material can also serve as a heat-resistant, flat and at the same time stable substrate in semiconductor applications for high clock rates, or to consolidate a large number of radio antennas into the smallest space, as will be required for the next evolutionary stage in the mobile telephony, known as ‘5G’.

If you are the last glass manufacturer for optical glass in the Western world, where is your competition?
Our competitors in this area can be found in Japan, for instance, but there are increasing numbers of new competitors establishing operations in China as well. This drives us to become even better in terms of quality and customer orientation; we are also aided in this by our long tradition as a manufacturer of special glass with strong locations in Germany.

You are represented in the field of architecture, too. How are you helping shape our modern building culture?
That’s right, we’re active with several business units in the field of architecture, including the “processed glass” area. Here, we provide glass to partners that process it further. A recent example is the newly opened Council building of the European Union in Brussels. Our anti-reflective Amiran is used in glazing for the interpreters’ booths there. The glass allows interpreters positioned a storey above the Council Chamber to observe the proceedings below without annoying reflections, and to translate these in real time. This shows how close to life, and how prominently our products are often placed without being visible to outsiders.

Particularly in the field of culture, your company plays an important role with its glass products, including for museum display cases, restoration of windows in historic buildings and monuments, etc. What makes you unique in this regard?
In these areas we can score through very high quality and our unique production in Germany. Applying the Fourcault drawing process, we also produce architectural glass, in addition to other technical glasses. This sophisticated production method, which industrialised the production of architectural glass at the beginning of the 20th century, allows us to manufacture the glass with the necessary characteristics required for the restoration of historic façades. This way, Schott can supply the right glass, primarily for structures that date to the Bauhaus era, but also for older historical buildings. What is characteristic of these glass types is that they combine the latest insulation and sun-protection capabilities with a true-to-original, old-fashioned look.

How will glass as a material, and its applications, change our lives in future?
Glass is truly a miracle material. Imagine homes or cars without windows. If not for glass, these developments as we know them today would not have been possible to begin with. But not all glass is alike, so we are investing a great deal of energy and capacity towards developing and refining the material – through coatings or new production processes, for example. The fact that we are successful in this can be seen in the ever-new innovations using this material, innovations such as ultra-thin glass as thin as a human hair but which can be chemically hardened. This is a combination no one would have thought possible just a few years ago. We are already series producing glass types such as this today. So my answer is: yes, glass has the potential to change our lives in significant ways in the future.

In what other areas might glass be used in future, and what could the next steps of technology make possible in this regard?
There is no universal answer here, but let’s take glass on a spool. This ultra-thin glass is wound on a spool and can be rolled from it, too. This could change entire industries and transform production steps, calling gridlocked ways of thinking into question. Ultra-thin glass might be applied the way a “film” would wherever extreme conditions take current polymer solutions to the limits of the feasible, e.g. in solar applications or printed electronics.
But this is just one of many examples that come to mind. Our research and development is currently working on an ion-conductive glass-ceramic powder for the next generation of batteries in electric vehicles. Another project is looking into series production of innovative fluorescent conversion ceramics in light converters for highly energy efficient digital projectors – great cinema, you might say. That is exactly what I value about the world of Schott.

schott.com


Christoph Fark

Christoph Fark is a graduate in industrial engineering and has been working with Schott since September 2003. He has been in charge of the business unit advanced optics since 2014. Prior to joining Schott, he held several international positions at Kermi GmbH (formerly a Preussag subsidiary).


This article was published in The Produktkulturmagazin, issue Q2 2017. Picture credit © SCHOTT

produktkulturmagazin.de

 

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