Mr. Ralf Freiberger Profile

Ralf Freiberger

at RWTH Aachen Univ

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Author

Publications (3)

Proceedings Article | 4 May 2011 Paper

Time resolved EUV pump-probe microscopy of fs-LASER induced nanostructure formation

R. Freiberger, J. Hauck, M. Reininghaus, D. Wortmann, L. Juschkin

Proceedings Volume 8076, 80760K (2011) https://doi.org/10.1117/12.886872

KEYWORDS: Extreme ultraviolet, Spatial resolution, Nanostructures, Microscopy, Sensors, Microchannel plates, Plasma, Zone plates, Microscopes, Oxygen

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We report on our efforts in design and construction of a compact Extreme Ultraviolet (EUV)-pump-probe microscope. The goal is the observation of formation of nanostructures, induced by a femtosecond (fs)-laser pulse. The unique interaction processes of fs-laser radiation with matter open up new markets in laser material processing and, therefore, are actively investigated in the last decade. The resulting "sub 100 nm"-structures offer vast potential benefits in photonics, biotechnology, tribological surface design, plasmonic applications and production of nanoparticles. Focused fs-laser radiation causes a local modification resulting in nanostructures of high precision and reproducibility. However the formation dynamics is not well understood. Research in this field requires high temporal and spatial resolution. A combination of fs-laser and EUV-microscope provides a tool for "in situ"-observation of the formation dynamics. As exemplary structures to be investigated, we use nanojets on thin gold films and periodic surface structures (ripples) on dielectrics. In the future, the EUV-pump-probe microscope can become a versatile tool to observe physical or biological processes. Microscopy using EUV-light is capable of detecting structures on a scale down to several tens of nanometers. For detailed investigations a compact EUV-microscope has been realized utilizing O^VI Balmer-alpha radiation at 17.3 nm coming from a discharge produced oxygen plasma. As optical elements a grazing incidence elliptical collector and a zone plate with a width of outermost zone of 50 nm and a spectral filter to avoid chromatic aberrations are used. The detector is a fast gated microchannel plate with a pore size of 2 microns contacted by a low impedance transmission line. The expected spatial resolution of the setup is better than 100 nm and the time resolution is better than 1 ns. The newly developed EUV-microscope is a powerful tool for a wide field of investigations that need high time and spatial resolutions simultaneously.

Proceedings Article | 4 May 2011 Paper

Performance benchmark of a gateable microchannel plate detector for extreme ultraviolet radiation with high temporal resolution

Johannes Hauck, Ralf Freiberger, Larissa Juschkin

Proceedings Volume 8076, 80760R (2011) https://doi.org/10.1117/12.887017

KEYWORDS: Sensors, Extreme ultraviolet, Microchannel plates, Spatial resolution, Microscopes, Modulation transfer functions, Optical filters, Temporal resolution, Photons, Capacitance

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Proceedings Article | 30 April 2009 Paper

Two magnification steps EUV microscopy with a Schwarzschild objective and an adapted zone plate lens

Larissa Juschkin, Ralf Freiberger

Proceedings Volume 7360, 736005 (2009) https://doi.org/10.1117/12.822986

KEYWORDS: Zone plates, Objectives, Extreme ultraviolet, Sensors, Microscopy, Microscopes, Mirrors, Image resolution, Multilayers, Photomasks

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