SC3 / EXTREME LIGHT SOURCES
Classical light microscopy has been instrumental in discovering the world of small structures and analyzing objects such as bacteria, conversely coherent laser light provides us with ultrashort pulses, and thereby allows us to explore the dynamics of the shortest events. Today, femtosecond (10-15s) laser pulses are routinely employed to probe and even control chemical reactions. Along these lines, the 1995 Nobel prize in physics was awarded for the coherent control of quantum systems . However, both spatial and temporal resolution are intrinsically limited by the wavelength of the used light (approx. 400 - 800 nm for the visible range). In order to gain more detailed insights into the structure of matter at atomic length- and time scales (10-10m) and 10-18s, respectively), coherent sources with substantially shorter wavelengths in the XUV and X-ray regime (100 nm - 0.1 nm) are of paramount importance.
Advanced microscopy- and spectroscopy techniques are eager to harness these new tools to monitor and control the dynamics of atoms, molecules and proteins in real time . Consequently, an ever growing demand and availability for extreme light sources exists across medicine, pharmaceutics, biology, chemistry and physics. Furthermore, the production of integrated circuits for use in computers or mobile phones profits from this development as the manufacturing process depends on the control of light of very short wavelengths .
Currently, two complementary approaches exist:
- Free electron lasers (FELs) can span the entire XUV and X-ray spectral region and require major research facilities for their operation. In addition to already existing FELs such as FLASH at the German electron synchrotron (DESY) in Hamburg or Linac Coherent Light Source (LCLS) at the Stanford linear accelerator (SLAC), a number of additional sources is currently under construction (XFEL at DESY, LCLS II at SLAC) . The budget of these facilities typically lies on the order of 1.2 bn. Euros .
- Laser-driven XUV- and X-ray sources complement FELs. In comparison those sources have less power but produce the shortest pulses to date (< 100 attoseconds). Pulse durations in the sub-attosecond, the so-called Zeptosecond range (10-21 s)  are planned for the first major research installation of this type .
Ultrashort laser pulses can be used to monitor extremely fast processes in atoms , organic molecules  and solids . Therefore determinant progress is expected in the following fields :
- Fundamental research: The observations of structures at atomic length- and time scales enables the probing of yet unknown dynamics in solids and macromolecules.
- Medicine / Healthcare / Pharmacology: The chemical functionality of biologically relevant complexes is the result of extremely fast processes, that will be observed and controlled in real time on the level of individual atoms.
- Energy: Light-harvesting complexes that convert photons into chemical energy could finally be investigated and understood, thereby enabling new strategies for a sustainable global energy supply.
- Material science / IT: The magnetic and electronic properties of nanocrystals and atom clusters are rooted in their intrinsic structure. Increasing our knowledge of those fundamental properties is the basis for future developments in information technology and will play a crucial role in decoupling the exponential growths of data volume and its respective energy consumption.
The main challenge in all these scenarios lies in the design and manufacturing of optical components that can meet the extreme demands of maintaining polarization, pulse shape, spectrum and beam profile in this spectral range. Of particular importance will be laser-driven table-top sources, which promise significant progress in the near future. A focus area will be ultra-precise freeform optical elements based on high-performance (amorphous and crystalline) materials functionalized by polishing as well as nanostructure and layer deposition technologies.
For biomedical applications, the so-called "water window" between 2 - 4 nm plays a central role. Current mirrors for this spectral range only exhibit reflectivities 14%-25%, or about one third of the theoretical optimum of 39%-57% . Clearly, here significant progress has to be made to lose only a few of the precious photons. The efficiency of future complex optical arrangements therefore will have to increase by an order of magnitude or more.
ENABLER: FUNCTIONALIZED FREEFORM SURFACES
In recent years, the purposeful manipulation of light has been brought to perfection in the visible and near infrared. Various properties such as bandwidth, pulse length, intensity and polarization can be independently controlled, allowing for the synthesis of almost arbitrary pulse shapes. These, in turn, are indispensable for the coherent control of chemical reactions  and the generation of attosecond pulses .
In order to achieve the same degree of fidelity and flexibility on the XUV and X-ray regime, the following challenges have to be overcome:
- The control of wavelength and spectral bandwidth is key for the resolution of spectroscopic and microscopic methods.
- In order to resolve processes on atomic time scales, variable pulses down to the zeptosecond range are required. Compatible optical elements will have to exceed the current state of the art by several orders of magnitude .
Due to the typically high absorption and dispersion, XUV and X-ray optics are typically realized in reflection. However, due to the low refractive index contrast, this approach usually requires operation in grazing incidence, and correspondingly demands large optical surfaces. In addition, the short wavelengths pose extremely stringent requirements on the shape accuracy as well as the roughness of optical surfaces. These challenges are illustrated by the fact that a surface accuracy of <1 nm is necessary to reflect attosecond pulses without distortions.
Optics for extreme light sources require substrates with highest shape accuracy and lowest roughness to be supplied. In order to allow for a broad range of applications, the fabrication of optical freeforms for large geometric dimensions is of key importance. In addition, the optics have to be smoothened with high-grade polishing techniques. Additional functionalizations of the surface by means of layer deposition or nanostructuring must not compromise the surface quality.
Along these lines, the key technological challenges are as follows:
- Technologies for the surface treatment of optical components for short wavelengths (freeform definition and polishing techniques),
- Methods for high-precision coating (e.g. atomic layer deposition, ALD), in particular on freeform surfaces, with high-quality metallic and dielectric materials,
- Extension of the application range of nanostructures towards shorter wavelengths,
- High-resolution characterization technologies for nanostructures (scanning electron microscopy, atomic force microscopy, scattered-light characterization) on large substrates and freeforms.
The applicant has long-standing expertise in the development and implementation of the required technologies, as evidenced by numerous projects related to optical layers, nanostructuring and characterization. The required processing facilities, technologies and measurement techniques for the planned evolution of the technology chains will be developed in cooperation with users and industrial partners.
To meet the abovementioned requirements, the following investments for the core technologies are necessary
IMPORTANT PROJECTS OF THE NPL-PARTNERS
- Fluorid-Beschichtung von ebenen Beamline-Spiegeln für BESSY II bei Helmholtz-Zentrum Berlin.
- Multilayer-Zylinderspiegel für 2,3 bis 9,5 keV for BESSY II at Helmholtz-Zentrum Berlin link
- Pt, Au und C Beschichtung für Beamline-Gittermonochromator for BESSY II at Helmholtz-Zentrum Berlin link
- Fluorid-Beschichtung von ebenen Beamline-Spiegeln for BESSY II at Helmholtz-Zentrum Berlin link
- Beamline-Spiegel für 10 … 100 nm for Broadband Beamline at Paul Scherrer Institut (PSI).
- Fokussierspiegel für 13,9 und 18,9 nm for EUV-Kamera at Xtreme technologies GmbH.
- Z-Spiegel Kombination für 13,5 nm for EUV-Kamera at Xtreme technologies GmbH.
- EUV-Schwarzschild-Objektiv für 13,5 nm for EUV-Mikroskop at Fraunhofer-Institut für Lasertechnik (ILT) link
- EUV-Schwarzschild-Objektiv für 13,5 nm for FLASH at Deutsches Elektronensynchrotron (DESY) in Zusammenarbeit mit RheinAhrCampus Remagen.
- Refokussierspiegel für 107, 186 und 288 eV for FLASH at Deutsches Elektronensynchrotron (DESY) link
- Fokussierspiegel für 18,9 nm for Fokussierung von Röntgenlaserstrahlung at Max-Born-Institut (MBI) link
- Z-Spiegel Kombination für 9, 10, 13 und 30 nm for High Harmonics Beamline at ARC Centre of Excellence for Coherent X-Ray Science, Swinburne University of Technology link
- Z-Spiegel Kombination für 52.6 nm for High Harmonics Beamline at University of Southampton.
- Z-Spiegel Kombination für 90, 120, 150 und 288 eV for High Harmonics Beamline at Gesellschaft für Schwerionenforschung (GSI) link
- Z-Spiegel Kombination für 30 nm for High Harmonics Beamline at The University of Manchester.
- Z-Spiegel Kombination für 13,7 nm for High Harmonics Beamline at Rutherford Appleton Laboratory link
- Z-Spiegel Kombination für 92 eV for High Harmonics Beamline at Deutsches Elektronensynchrotron (DESY).
- Z-Spiegel Kombination für 52.6 nm for High Harmonics Beamline at University of Southampton.
- Z-Spiegel Kombination für 13 und 30 nm for High Harmonics Beamline at Institute national de la recherche scientifique (INRS).
- Z-Spiegel Kombination für 10,9 / 17,3 / 19,3 und 24,3 nm for High Harmonics Beamline at Forschungszentrum Jülich link
- EUV-Schwarzschild-Objektiv für 13,5 nm for Kollektor-Optik für LPP-Quelle at Laserlaboratorium Göttingen link
- Beschichtung von EUV-Kollektorspiegeln for LPP-Quelle für EUV-Lithographie-Tool NXE:3100 at ASML link
- Refurbishment von EUV-Kollektorspiegeln for LPP-Quelle für EUV-Lithographie-Tool NXE:3100 at ASML link
- EUV-Kollektorspiegel für 13,5 nm for LPP-Quelle für Metrology-Anwendungen at Eidgenössische Technische Hochschule (ETH).
- Kollektorspiegel für das Wasserfenster für 2,478 nm for LPP-Quelle für Wasserfenster-Mikroskope at Royal Institute of Technology in Stockholm (KTH) in Zusammenarbeit mit Max-Born-Institut (MBI).
- Characterization and metrology for Multilayer optics at Fraunhofer IOF link
- Beam Splitter Grating for XUV-Interferometer for National Synchrotron Radiation Laboratory (NSRL) at University of Science and Technology of China link
- Characterization and metrology for Optical components for EUV-Lithography at ASML link
- Characterization and metrology for Optical components for EUV-Lithography at SeNaTe link
- Characterization and metrology for Optical components for EUV-Lithography at Carl Zeiss SMT GmbH link
- Characterization and metrology for Optical components for EUV-Lithography at optiX fab GmbH link
- EUV-Schwarzschild-Objektiv für 13,5 nm for Reflektometer für Wolter-Teleskope at Laserzentrum Hannover (LZH).
- Beschichtung von ebenen und sphärischen Spiegeln für 13,5 nm for SHARP-Microscope Facility at Center for X-Ray Optics (CXRO) link
- Characterization and metrology for X-ray detectors at The French Alternative Energies and Atomic Energy Commission (CEA) link
- Characterization and metrology for X-ray detectors at Massachusetts Institute of Technology (MIT) link
- Characterization and metrology for X-ray detectors at DECTRIS Ltd. link
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 Eli attosecond.
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- laser-driven EUV and x-ray sources as well as attosecond systems
- Free electron lasers
- Medicine / Health / Pharmacy
- Materials science / IT
- Basic physics
- structured free-form layers of the highest quality
For shorter XUV wavelengths the increase of the supported bandwidth main-taining sufficiently high reflectance is a current technological challenge.