Mr. Mark Gyamfi Profile

Mark Gyamfi

at Laser Zentrum Hannover eV

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Publications (8)

Proceedings Article | 22 March 2018 Paper

Approaches toward optimized laser-induced damage thresholds of dispersive compensating mirrors applying nanolaminates

T. Willemsen, M. Brinkmann, M. Jupé, M. Gyamfi, S. Schlichting, D. Ristau

Proceedings Volume 10447, 1044712 (2018) https://doi.org/10.1117/12.2281126

KEYWORDS: Mirrors, Refractive index, Dielectrics, Laser damage threshold, Optics manufacturing, Quantum wells

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Proceedings Article | 6 December 2016 Paper

Dual wavelength laser damage mechanisms in the ultra-short pulse regime

Mark Gyamfi, Marion Costella, Thomas Willemsen, Peter Jürgens, Mathias Mende, Lars Jensen, Detlev Ristau

Proceedings Volume 10014, 100141B (2016) https://doi.org/10.1117/12.2245156

KEYWORDS: Laser induced damage, Laser damage threshold, Reflectivity, Mirrors, Hybrid fiber optics, Aluminum, Niobium, Tantalum, Refractive index, Femtosecond phenomena

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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

Proceedings Volume 10014, 100141Z (2016) https://doi.org/10.1117/12.2244835

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

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Proceedings Article | 6 December 2016 Paper

Ultrafast polychromatic ionization of dielectric solids

P. Jürgens, M. Jupé, M. Gyamfi, D. Ristau

Proceedings Volume 10014, 100141C (2016) https://doi.org/10.1117/12.2244833

KEYWORDS: Ionization, Laser damage threshold, Electrons, Dielectrics, Solids, Ultrafast phenomena, Photons, Laser induced damage, Pulsed laser operation, Absorption

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The modeling of the laser-induced damage processes can be divided into thermal and electronic processes. Especially, electronic damage seems to be well understood. In corresponding models, the damage threshold is linked to the excitation of valence electrons into the conduction band, and often the damage is obtained if a critical density of free electrons is exceeded. For the modeling of the electronic excitation, rate equation models are applied which can vary in the different terms representing different excitation channels. According to the current state of the art, photoionization and avalanche ionization contribute the major part to the ionization process, and consequently the determination of laser-induced damage thresholds is based on the calculation of the respective terms. For the theoretical description of both, well established models are available. For the quantitative calculation of the photoionization, the Keldysh theory is used most frequently, and for the avalanche processes the Drude theory is often applied. Both, Drude and Keldysh theory calculations depend on the laser frequency and use a monochromatic approach. For most applications the monochromatic description matches very well with the experimental findings, but in the range of few-cycle pulses the necessary broadening of the laser emission spectrum leads to high uncertainty for the calculation. In this paper, a novel polychromatic approach is presented including photo- and avalanche ionization as well as the critical electron density. The simulation combines different ionization channels in a Monte-Carlo procedure according to the frequency distribution of the spectrum. The resulting influence on the wavelength and material dependency is discussed in detail for various pulse shapes and pulse durations. The main focus of the investigation is concentrated on the specific characteristics in the dispersion and material dependency of the laser-induced damage threshold respecting the polychromatic characteristics of the ultra-short pulse (USP) laser damage.

Proceedings Article | 23 November 2015 Paper

Lowering evaluation uncertainties in laser-induced damage testing

Lars Jensen, Marius Mrohs, Mark Gyamfi, Heinrich Mädebach, Detlev Ristau

Proceedings Volume 9632, 96321J (2015) https://doi.org/10.1117/12.2194944

KEYWORDS: Laser marking, Laser induced damage, Error analysis, Data modeling, Laser damage threshold, Standards development, Probability theory, Pulsed laser operation, Statistical analysis, Reflectivity, Mirrors

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Proceedings Article | 23 November 2015 Paper

Delay dependency of two-pulse femtosecond laser damage

Mark Gyamfi, Peter Jürgens, Lars Jensen, Detlev Ristau

Proceedings Volume 9632, 96320W (2015) https://doi.org/10.1117/12.2194778

KEYWORDS: Femtosecond phenomena, Laser damage threshold, Photons, Ultrafast phenomena, Optical components, Frequency conversion, Ionization, Mirrors, Standards development, Absorption, Neodymium, Laser induced damage, Pulsed laser operation, Dielectrics

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Proceedings Article | 2 October 2015 Paper

Advanced femtosecond laser coatings raise damage thresholds

Hans Becker, Diana Tonova, Michael Sundermann, Lars Jensen, Mark Gyamfi, Detlev Ristau, Mathias Mende

Proceedings Volume 9627, 962716 (2015) https://doi.org/10.1117/12.2191225

KEYWORDS: Mirrors, Laser damage threshold, Interfaces, Femtosecond phenomena, Optical coatings, Silica, Refractive index, Laser induced damage, Plasma etching, Reflection

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Proceedings Article | 18 November 2014 Paper

Dual-wavelength ultra-short pulse laser damage testing

Mark Gyamfi, Peter Jürgens, Mathias Mende, Lars Jensen, Detlev Ristau

Proceedings Volume 9237, 92371Q (2014) https://doi.org/10.1117/12.2068180

KEYWORDS: Electrons, Laser damage threshold, Ionization, Laser induced damage, Mirrors, Absorption, Data modeling, Femtosecond phenomena, Pulsed laser operation, Laser systems engineering

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Showing 5 of 8 publications

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