Dr. Henrik Ehlers Profile

Dr. Henrik Ehlers

at Laser Zentrum Hannover e.V.

SPIE Involvement:

Author

Publications (24)

Proceedings Article | 6 December 2016 Paper

Improved LIDT values for dielectric dispersive compensating mirrors applying ternary composites

T. Willemsen, S. Schlichting, M. Gyamfi, M. Jupé, H. Ehlers, U. Morgner, D. Ristau

Proc. SPIE. 10014, Laser-Induced Damage in Optical Materials 2016

KEYWORDS: Mirrors, Curium, Detection and tracking algorithms, Laser induced damage, Composites, Dielectrics, Laser damage threshold, Tantalum, Dielectric mirrors, Reverse engineering

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Proceedings Article | 23 September 2015 Paper

Properties of transparent organic-inorganic composite coatings prepared by ion beam sputtering of PTFE and Al2O3

Melanie Gauch, Henrik Ehlers, Detlev Ristau

Proc. SPIE. 9627, Optical Systems Design 2015: Advances in Optical Thin Films V

KEYWORDS: Refractive index, FT-IR spectroscopy, Scattering, Sputter deposition, Composites, Optical coatings, Oxygen, Ion beams, Fluorine, Absorption

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Proceedings Article | 23 September 2015 Paper

Precise fabrication of ultra violet dielectric dispersion compensating mirrors

T. Willemsen, S. Schlichting, T. Kellermann, M. Jupé, H. Ehlers, U. Morgner, D. Ristau

Proc. SPIE. 9627, Optical Systems Design 2015: Advances in Optical Thin Films V

KEYWORDS: Near infrared, Mirrors, Silica, Spectroscopy, Ultraviolet radiation, In situ metrology, Reflectivity, Solids, Dielectric mirrors, Dielectric dispersion

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Proceedings Article | 23 September 2015 Paper

Direct in situ GDD measurement in optical coating process

S. Schlichting, T. Willemsen, H. Ehlers, U. Morgner, D. Ristau

Proc. SPIE. 9627, Optical Systems Design 2015: Advances in Optical Thin Films V

KEYWORDS: Mirrors, Light sources, Spectroscopy, In situ metrology, Coating, Optical coatings, Interferometry, Optical testing, Algorithm development, Michelson interferometers

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Proceedings Article | 23 September 2015 Paper

Simulation in thin film technology

Marcus Turowski, Marco Jupé, Henrik Ehlers, Thomas Melzig, Andreas Pflug, Detlev Ristau

Proc. SPIE. 9627, Optical Systems Design 2015: Advances in Optical Thin Films V

KEYWORDS: Thin films, Titanium dioxide, Optical properties, Sputter deposition, Particles, Coating, Computer simulations, Monte Carlo methods, Thin film growth, Fused deposition modeling

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Proceedings Article | 4 December 2012 Paper

Applying hafnia mixtures to enhance the laser-induced damage threshold of coatings for third-harmonic generation optics

Mathias Mende, Lars Jensen, Henrik Ehlers, Stefan Bruns, Michael Vergöhl, Peer Burdack, Detlev Ristau

Proc. SPIE. 8530, Laser-Induced Damage in Optical Materials: 2012

KEYWORDS: Thin films, Refractive index, Antireflective coatings, Silica, Laser induced damage, Annealing, Optical coatings, Laser damage threshold, Nonlinear crystals, Thin film coatings

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Proceedings Article | 29 November 2012 Paper

An exhaustive study of laser damage in ion beam sputtered pure and mixture oxide thin films at 1030 nm with 500 fs pulse durations

Laurent Gallais, Benoit Mangote, Mireille Commandré, Mathias Mende, Lars Jensen, Henrik Ehlers, Marco Jupé, Detlev Ristau, Andrius Melninkaitis, Valdas Sirutkaitis, Simonas Kičas, Tomas Tolenis, Ramutis Drazdys

Proc. SPIE. 8530, Laser-Induced Damage in Optical Materials: 2012

KEYWORDS: Oxides, Thin films, Refractive index, Silica, Laser induced damage, Optical coatings, Ion beams, Laser damage threshold, Thin film coatings, Zirconium dioxide

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Proceedings Article | 5 October 2011 Paper

Study of the laser matter interaction in the femtosecond regime: application to the analysis of the laser damage of optical thin films

B. Mangote, L. Gallais, M. Zerrad, M. Commandré, L. Gao, F. Lemarchand, M. Lequime, A. Melninkaitis, J. Mirauskas, V. Sirutkaitis, S. Kicas, T. Tolenis, R. Drazdys, M. Mende, L. Jensen, H. Ehlers, D. Ristau

Proc. SPIE. 8168, Advances in Optical Thin Films IV

KEYWORDS: Oxides, Thin films, Refractive index, Femtosecond phenomena, Silica, Sputter deposition, Laser induced damage, Optical coatings, Laser damage threshold, Laser optics

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Proceedings Article | 4 October 2011 Paper

Laser-induced damage of pure and mixture material high reflectors for 355nm and 1064nm wavelength

Mathias Mende, Lars Jensen, Henrik Ehlers, Werner Riggers, Holger Blaschke, Detlev Ristau

Proc. SPIE. 8168, Advances in Optical Thin Films IV

KEYWORDS: Reflectors, Refractive index, Multilayers, Silica, Laser induced damage, Optical coatings, Transmission electron microscopy, Ion beams, Hybrid fiber optics, Absorption

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High reflecting multilayer coatings play a key role for many applications of pulsed Nd:YAG high power lasers in industry and science. In the present contribution, improvements in the optical properties and the radiation resistance of high reflectors for 355nm and 1064nm wavelength on the basis of mixture materials are discussed. Within a co-operation between the LASEROPTIK GmbH and the Laser Zentrum Hannover e.V., several deposition processes including Ion Beam Sputtering, Magnetron Sputtering, and Electron Beam Evaporation could be addressed for this study. The selected material combinations HfO₂+ZrO₂/SiO₂, HfO₂+Al₂O₃/SiO₂, HfO₂+SiO₂/SiO₂ and HfO₂/SiO₂ were deposited using a zone target assembly for the IBS technique or defined material mixtures for the evaporation process. Single layers of the applied mixtures were analyzed by UV/Vis/NIR spectroscopy to correlate the optical constants with the atomic compositions quantified by Energy Dispersive X-ray Spectroscopy (EDX) and X-ray Photoelectron Spectroscopy (XPS). In addition to pure material reference mirrors and reflecting multilayer coatings with high index material mixtures, also interference coatings consisting of nanolaminates as well as multilayer systems with refractive index profiles were produced. The laser induced damage thresholds at 1064nm wavelength for nanosecond pulse durations were measured in a 1000on1 experiment complying with the standard ISO11254. For the 355nm high reflectors, the radiation resistance was determined in a 10000on1 procedure, furthermore, the radiation-induced absorption was measured by laser calorimetry according to ISO11551. Finally, the layer interfaces and the amorphous microstructure of selected multilayers were analyzed by Transmission Electron Microscopy (TEM) to obtain detailed information about possible partial crystallinity. The results are interpreted in the context of former investigations on the power handling capability of coating systems involving material mixtures.

Proceedings Article | 4 October 2011 Paper

Online re-optimization as a powerful part of enhanced strategies in optical broadband monitoring

S. Schlichting, K. Heinrich, H. Ehlers, D. Ristau

Proc. SPIE. 8168, Advances in Optical Thin Films IV

KEYWORDS: Multilayers, Detection and tracking algorithms, Titanium dioxide, Coating, Computer simulations, Process control, Transmittance, Algorithm development, Virtual reality, Optics manufacturing

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Proceedings Article | 4 October 2011 Paper

Optical and mechanical properties of oxide UV coatings, prepared by PVD techniques

Olaf Stenzel, Mark Schürmann, Steffen Wilbrandt, Norbert Kaiser, Andreas Tünnermann, Mathias Mende, Henrik Ehlers, Detlev Ristau, Stefan Bruns, Michael Vergöhl, Werner Riggers, Martin Bischoff, Mario Held

Proc. SPIE. 8168, Advances in Optical Thin Films IV

KEYWORDS: Oxides, Thin films, Refractive index, Silica, Glasses, Ultraviolet radiation, Silicon, Coating, Semiconducting wafers, Temperature metrology

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Proceedings Article | 4 October 2011 Paper

From independent thickness monitoring to adaptive manufacturing: advanced deposition control of complex optical coatings

Henrik Ehlers, Sebastian Schlichting, Carsten Schmitz, Detlev Ristau

Proc. SPIE. 8168, Advances in Optical Thin Films IV

KEYWORDS: Titanium dioxide, Quartz, Crystals, Coating, Manufacturing, Optical coatings, Process control, Transmittance, Optics manufacturing, Crystal optics

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Proceedings Article | 22 April 2009 Paper

Long term tests of resonator optics in ArF excimer lasers

Nils Beermann, Holger Blaschke, Henrik Ehlers, Detlev Ristau, Dirk Wulff-Molder, Sigrid Jukresch, Ansgar Matern, Martin Bischoff, Dieter Gäbler, Norbert Kaiser

Proc. SPIE. 7131, XVII International Symposium on Gas Flow, Chemical Lasers, and High-Power Lasers

KEYWORDS: Reflectors, Mirrors, Contamination, Resonators, Crystals, Interfaces, Optical coatings, Laser resonators, Excimer lasers, Laser optics

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Proceedings Article | 30 December 2008 Paper

Investigation in the degradation of CaF2 outcouplers in excimer lasers operating at 193nm

H. Blaschke, N. Beermann, H. Ehlers, D. Ristau, M. Bischoff, D. Gäbler, N. Kaiser, A. Matern, D. Wulff-Molder

Proc. SPIE. 7132, Laser-Induced Damage in Optical Materials: 2008

KEYWORDS: Reflectors, Crystals, Interfaces, Ions, Coating, Reflectivity, Carbonates, Electron microscopy, Transmittance, Excimer lasers

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Proceedings Article | 25 September 2008 Paper

Optimization and characterization of transparent photocatalytic TiO2 thin films prepared by ion-assisted deposition

Redouan Boughaled, Sebastian Schlichting, Henrik Ehlers, Detlev Ristau, Inga Bannat, Michael Wark

Proc. SPIE. 7101, Advances in Optical Thin Films III

KEYWORDS: Thin films, Titanium dioxide, Image processing, Ultraviolet radiation, Crystals, Ions, Optical coatings, Oxygen, Deposition processes, Thin film coatings

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Proceedings Article | 25 September 2008 Paper

State of the art in deterministic production of optical thin films

D. Ristau, H. Ehlers, S. Schlichting, M. Lappschies

Proc. SPIE. 7101, Advances in Optical Thin Films III

KEYWORDS: Optical filters, Refractive index, Switching, Detection and tracking algorithms, Quartz, Sputter deposition, Crystals, Optical coatings, Control systems, Deposition processes

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Proceedings Article | 25 September 2008 Paper

Reliable production of steep edge interference filters

Marc Lappschies, Peter Pfeifer, Uwe Schallenberg, Henrik Ehlers, Detlev Ristau

Proc. SPIE. 7101, Advances in Optical Thin Films III

KEYWORDS: Optical filters, Refractive index, Sensors, Spectroscopy, Ions, Interference filters, Coating, Linear filtering, Transmittance, Deposition processes

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Proceedings Article | 25 September 2008 Paper

A method for the determination of substrate temperature during thin film coating deposition

St. Günster, H. Ehlers, D. Ristau

Proc. SPIE. 7101, Advances in Optical Thin Films III

KEYWORDS: Quartz, Glasses, Silicon, Optical coatings, Transmittance, Deposition processes, Vacuum ultraviolet, Thin film coatings, Temperature metrology, Absorption

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Proceedings Article | 15 January 2007 Paper

Damage threshold investigations of high-power laser optics under atmospheric and vacuum conditions

L. Jensen, M. Jupé, H. Mädebach, H. Ehlers, K. Starke, D. Ristau, W. Riede, P. Allenspacher, H. Schroeder

Proc. SPIE. 6403, Laser-Induced Damage in Optical Materials: 2006

KEYWORDS: Antireflective coatings, Aerospace engineering, Dielectrics, Ions, Coating, Transmittance, Laser damage threshold, Tantalum, Laser optics, Atmospheric optics

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Proceedings Article | 5 October 2005 Paper

Ion source characterization based on an array of retarding field analyzers

N. Beermann, H. Ehlers, D. Ristau

Proc. SPIE. 5963, Advances in Optical Thin Films II

KEYWORDS: Energy efficiency, Silica, Ions, Coating, Optical coatings, 3D metrology, Deposition processes, Data centers, Resolution enhancement technologies, Plasma

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Proceedings Article | 25 February 2004 Paper

Ion-assisted deposition processes: industrial network IntIon

Henrik Ehlers, Karl-Josef Becker, Rudolf Beckmann, Nils Beermann, Ulf Brauneck, Peter Fuhrberg, Dieter Gaebler, Stefan Jakobs, Norbert Kaiser, Michael Kennedy, Friedrich Koenig, Sven Laux, Juergen Christian Mueller, Bernd Rau, Werner Riggers, Detlev Ristau, Dieter Schaefer, Olaf Stenzel

Proc. SPIE. 5250, Advances in Optical Thin Films

KEYWORDS: Refractive index, Ions, Coating, Oxygen, Deposition processes, Niobium, Prototyping, Resolution enhancement technologies, Plasma, Absorption

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Proceedings Article | 25 February 2004 Paper

Ion-assisted deposition processes for precision and laser optics

Henrik Ehlers, Tobias Gross, Marc Lappschies, Detlev Ristau

Proc. SPIE. 5250, Advances in Optical Thin Films

KEYWORDS: Quartz, In situ metrology, Ions, Optical coatings, Process control, Transmittance, Deposition processes, Tantalum, Thin film coatings, Absorption

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Proceedings Article | 25 February 2004 Paper

Broadband optical monitoring for the deposition of complex coatings

Marc Lappschies, Tobias Gross, Henrik Ehlers, Detlev Ristau

Proc. SPIE. 5250, Advances in Optical Thin Films

KEYWORDS: Thin films, Refractive index, Detection and tracking algorithms, Data modeling, Optical coatings, Computing systems, Computer simulations, Transmittance, Deposition processes, Thin film coatings

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Proceedings Article | 7 September 1999 Paper

Broadband antireflection coatings deposited with ion-assisted evaporation

Sven Laux, Norbert Kaiser, Hansjoerg Niederwald, Michael Mertin, Henrik Ehlers, Detlev Ristau

Proc. SPIE. 3738, Advances in Optical Interference Coatings

KEYWORDS: Oxides, Refractive index, Antireflective coatings, Magnesium fluoride, Ions, Coating, Resistance, Reflectivity, Plasma, Absorption

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Showing 5 of 24 publications

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