A5022585209- Laser Material Processing Techniques
- Laser-induced spectroscopy and plasma
- Ocular and Laser Science Research
- Diamond and Carbon-based Materials Research
- Adhesion, Friction, and Surface Interactions
- Metal and Thin Film Mechanics
- Advanced Surface Polishing Techniques
- Cultural Heritage Materials Analysis
- Surface Roughness and Optical Measurements
- GaN-based semiconductor devices and materials
- Extraction and Separation Processes
- Solid State Laser Technologies
- Semiconductor Quantum Structures and Devices
- Chalcogenide Semiconductor Thin Films
- Laser Design and Applications
- Nonlinear Optical Materials Studies
- Laser-Ablation Synthesis of Nanoparticles
- Laser Applications in Dentistry and Medicine
- Solar Thermal and Photovoltaic Systems
- Ga2O3 and related materials
- Historical Influence and Diplomacy
- Semiconductor materials and interfaces
- Conservation Techniques and Studies
- Metal Alloys Wear and Properties
- Metallurgical Processes and Thermodynamics
University Medical Center Hamburg-Eppendorf
2024-2025
Universität Hamburg
2024-2025
Federal Institute For Materials Research and Testing
2015-2024
University Cancer Center Hamburg
2024
SP Technology (South Korea)
2024
Universität Greifswald
2011-2022
Innovent
2017
Czech Academy of Sciences, Institute of Physics
2016
Francophone University Association
2015
Moscow Institute of Thermal Technology
2015
We report measurements of the optical breakdown threshold and ablation depth in dielectrics with different band gaps for laser pulse durations ranging from 5 ps to fs at a carrier wavelength 780 nm. For $\ensuremath{\tau}<100\mathrm{fs}$, dominant channel free electron generation is found be either impact or multiphoton ionization (MPI) depending on size gap. The observed MPI rates are substantially lower than those predicted by Keldysh theory. demonstrate that sub-10-fs pulses open up way...
Laser-induced periodic surface structures (LIPSS, ripples) are a universal phenomenon and can be generated on almost any material upon irradiation with linearly polarized radiation. With the availability of ultrashort laser pulses, LIPSS have gained an increasing attraction during past decade, since these in simple single-step process, which allows nanostructuring for tailoring optical, mechanical, chemical properties. In this study, current state field is reviewed. Their formation...
The formation of laser-induced periodic surface structures (LIPSS) in different materials (metals, semiconductors, and dielectrics) upon irradiation with linearly polarized fs-laser pulses (τ ∼ 30–150 fs, λ 800 nm) air environment is studied experimentally theoretically. In metals, predominantly low-spatial-frequency-LIPSS periods close to the laser wavelength are observed perpendicular polarization. Under specific conditions, high-spatial-frequency-LIPSS sub-100-nm spatial (∼λ/10) can be...
The formation of nearly wavelength-sized laser-induced periodic surface structures (LIPSSs) on single-crystalline silicon upon irradiation with single or multiple femtosecond-laser pulses (pulse duration τ=130 fs and central wavelength λ=800 nm) in air is studied experimentally theoretically. In our theoretical approach, we model the LIPSS by combining generally accepted first-principles theory Sipe co-workers a Drude order to account for transient intrapulse changes optical properties...
The formation of nearly wavelength-sized laser-induced periodic surface structures (LIPSS) on single-crystalline silicon upon irradiation with single (N=1) and multiple (N≤1000) linearly polarized femtosecond (fs) laser pulses (pulse duration τ=130 fs, central wavelength λ=800 nm) in air is studied experimentally. Scanning electron microscopy (SEM) optical are used for imaging the ablated morphologies, both revealing LIPSS periodicities close to an orientation always perpendicular...
Laser-induced ablation has been extended down to a pulse duration of 20 fs generated by Ti sapphire laser system at wavelength 780 nm. Barium aluminum borosilicate glass with an extremely high transformation temperature (∼600 °C) served as target material. The most significant observation was substantial decrease the threshold fluence durations below 100 fs. All results indicate dominant role multiphoton absorption in addition collisional ionization this time domain.
The formation of laser-induced periodic surface structures (LIPSS) on two different silica polymorphs (single-crystalline synthetic quartz and commercial fused glass) upon irradiation in air with multiple linearly polarized single- double-fs-laser pulse sequences (τ = 150 fs duration, λ 800 nm center wavelength, temporal separation Δt &lt; 40 ps) is studied experimentally theoretically. Two distinct types fs-LIPSS [so-called low-spatial-frequency LIPSS (LSFL) high-spatial-frequency...
Periodic self-organization of matter beyond the diffraction limit is a puzzling phenomenon, typical both for surface and bulk ultrashort laser processing. Here we compare mechanisms periodic nanostructure formation on in fused silica. We show that volume nanogratings nanoripples having subwavelength periodicity oriented perpendicular to polarization share same electromagnetic origin. The orientation defined by near-field local enhancement vicinity inhomogeneous scattering centers. attributed...
Laser texturing is an emerging technology for generating surface functionalities on basis of optical, mechanical, or chemical properties. Taking benefit laser sources with ultrashort (fs) pulse durations features outstanding precision machining and negligible rims burrs surrounding the laser-irradiation zone. Consequently, additional mechanical post-processing steps are usually not required fs-laser (fs-LST). This work aimed to provide a bridge between research in field tribology materials...
In recent years, the improved understanding of formation laser-induced periodic surface structures (LIPSS) has led to an emerging variety applications that modify optical, mechanical, and chemical properties many materials. Such strongly depend on laser beam polarization are formed usually after irradiation with ultrashort linearly polarized pulses. The most accepted explanation for origin is based interference incident radiation electromagnetic waves propagate or scatter at irradiated This...
Chance discoveries of weapons, horse bones and human skeletal remains along the banks River Tollense led to a campaign research which has identified them as debris from Bronze Age battle. The resources war included horses, arrowheads wooden clubs, dead had suffered blows indicating face-to-face combat. This surprisingly modern decidedly vicious struggle took place over swampy braided streams river in an area settled, possibly coveted, territory. Washed by current, bodies weapons came rest on...
The formation of laser-induced periodic surface structures (LIPSS) upon irradiation silicon by multiple (N = 100) linearly polarized Ti:sapphire femtosecond laser pulses (duration τ 30 fs, center wavelength λ0 ∼ 790 nm) is studied experimentally in air and water environment. LIPSS morphologies are characterized scanning electron microscopy their spatial periods quantified two-dimensional Fourier analyses. It demonstrated that the environment significantly influences periodicity LIPSS. In...
The physical effects reducing the damage threshold of dielectric films when exposed to multiple femtosecond pulses are investigated. measured temperature increase a Ta2O5 film scales exponentially with pulse fluence. A polarized luminescence signal is observed that depends quadratically on fluence and attributed two-photon excitation self-trapped excitons form after band-to-band excitation. decreases increasing number, but independent repetition rate from 1 Hz kHz at constant number....