Anmelden

Open Access

  • Startseite
  • Suchen
  • Browsen
  • Veröffentlichen
  • Hilfe

Filtern

Autor

  • Bonse, Jörn (220)
  • Krüger, Jörg (86)
  • Rosenfeld, A. (37)
  • Höhm, S. (27)
  • Kirner, Sabrina V. (16)
  • Kautek, Wolfgang (15)
  • Eberstein, M. (14)
  • Spaltmann, Dirk (13)
  • Grehn, M. (12)
  • Mermillod-Blondin, A. (12)
+ weitere

Erscheinungsjahr

  • 2021 (1)
  • 2020 (19)
  • 2019 (19)
  • 2018 (15)
  • 2017 (22)
  • 2016 (10)
  • 2015 (10)
  • 2014 (14)
  • 2013 (18)
  • 2012 (16)
+ weitere

Dokumenttyp

  • Zeitschriftenartikel (108)
  • Vortrag (49)
  • Posterpräsentation (28)
  • Beitrag zu einem Tagungsband (24)
  • Buchkapitel (7)
  • Beitrag zu einem Sammelband (4)

Sprache

  • Englisch (161)
  • Deutsch (59)

Referierte Publikation

  • nein (117)
  • ja (103)

Schlagworte

  • Laser-induced periodic surface structures (LIPSS) (39)
  • Femtosecond laser ablation (38)
  • Femtosecond laser (24)
  • Surface functionalization (20)
  • Laser processing (16)
  • Laser ablation (15)
  • Silicon (11)
  • Applications (10)
  • Tribology (9)
  • Friction (8)
+ weitere

Organisationseinheit der BAM

  • 6 Materialchemie (96)
  • 6.2 Grenzflächenprozesse und Korrosion (96)
  • 9 Komponentensicherheit (21)
  • 9.5 Tribologie und Verschleißschutz (21)
  • 6.6 Physik und chemische Analytik der Polymere (5)
  • 6.7 Oberflächenmodifizierung und -messtechnik (4)
  • 6.1 Oberflächenanalytik und Grenzflächenchemie (3)
  • 4 Material und Umwelt (2)
  • 4.1 Biologische Materialschädigung und Referenzorganismen (2)
  • 5 Werkstofftechnik (1)
+ weitere

220 Treffer

  • 1 bis 10
  • CSV
  • RIS
  • 10
  • 20
  • 50
  • 100

Sortieren nach

  • Jahr
  • Jahr
  • Titel
  • Titel
  • Autor
  • Autor
Time-resolved imaging of laser-induced refractive index changes in transparent media (2011)
Mermillod-Blondin, A. ; Mauclair, C. ; Bonse, Jörn ; Stoian, R. ; Audouard, E. ; Rosenfeld, A. ; Hertel, I.V.
We describe a method to visualize ultrafast laser-induced refractive index changes in transparent materials with a 310 fs impulse response and a submicrometer spatial resolution. The temporal profile of the laser excitation sequence can be arbitrarily set on the subpicosecond and picosecond time scales with a pulse shaping unit, allowing for complex laser excitation. Time-resolved phase contrast microscopy reveals the real part of the refractive index change and complementary time-resolved optical transmission microscopy measurements give access to the imaginary part of the refractive index in the irradiated region. A femtosecond laser source probes the complex refractive index changes from the excitation time up to 1 ns, and a frequency-doubled Nd:YAG laser emitting 1 ns duration pulses is employed for collecting data at longer time delays, when the evolution is slow. We demonstrate the performance of our setup by studying the energy relaxation in a fused silica sample after irradiation with a double pulse sequence. The excitation pulses are separated by 3 ps. Our results show two dimensional refractive index maps at different times from 200 fs to 100 µs after the laser excitation. On the subpicosecond time scale we have access to the spatial characteristics of the energy deposition into the sample. At longer times (800 ps), time-resolved phase contrast microscopy shows the appearance of a strong compression wave emitted from the excited region. On the microsecond time scale, we observe energy transfer outside the irradiated region.
Time-resolved imaging of bulk a-SiO2 upon various ultrashort excitation sequences (2011)
Mermillod-Blondin, A. ; Mauclair, C. ; Rosenfeld, A. ; Bonse, Jörn ; Stoian, R. ; Audouard, E.
Ultrashort pulses lasers are tools of choice for functionalizing the bulk of transparent materials. In particular, direct photoinscription of simple photonic functions have been demonstrated. Those elementary functions rely on the local refractive index change induced when focusing an ultrashort pulse in the volume of a transparent material. The range of possibilities offered by direct photoinscription is still under investigation. To help understanding, optimizing and assessing the full potential of this method, we developed a time-resolved phase contrast microscopy setup. The imaginary part (absorption) and the real part of the laser-induced complex refractive index can be visualized in the irradiated region. The setup is based on a commercially available phase contrast microscope extended into a pump-probe scheme. The originality of our approach is that the illumination is performed by using a pulsed laser source (i.e. a probe beam). Speckle-related issues are solved by employing adequate sets of diffusers. This laser-microscopy technique has a spatial resolution of 650 nm, and the impulse response is about 300 fs. The laser-induced refractive index changes can be tracked up to milliseconds after the energy deposition. The excitation beam (the pump) is focused with a microscope objective (numerical aperture of 0.45) into the bulk of an a-SiO2 sample. The pump beam can be temporally shaped with a SLM-based pulse shaping unit. This additional degree of flexibility allows for observing different interaction regimes. For instance, bulk material processing with femtosecond and picosecond duration pulses will be studied.
X-ray emission during ultrashort pulse laser processing (2019)
Legall, Herbert ; Schwanke, Christoph ; Bonse, Jörn ; Krüger, Jörg
The industrial use of ultrashort laser pulses has made considerable progress in recent years. The reasons for this lie in the availability of high average powers at pulse repetition rates in the several 100 kHz range. The advantages of using ultrashort laser pulses in terms of processing precision can thus be fully exploited. However, high laser intensities on the workpiece can also lead to the generation of unwanted X-rays. Even if the emitted X-ray dose per pulse is low, the accumulated X-ray dose can become significant for high-repetition-rate laser systems so that X-ray exposure safety limits must be considered. The X-ray emission during ultrashort pulse laser processing was investigated for a pulse duration of 925 fs at 1030 nm wavelength and 400 kHz repetition rate. Industrially relevant materials such as steel,aluminum and glass were treated. Tungsten served as reference. X-ray spectra were recorded, and X-ray dose measurements were performed for laser treatment in air. For laser intensities > 2 × 10^13 W/cm2, X-ray doses exceeding the regulatory exposure limits for members of the public were found. Suitable X-ray protection strategies are proposed.
Large-area fabrication of low- and high-spatial-frequency laser-induced periodic surface structures on carbon fibers (2018)
Kunz, C. ; Büttner, T.N. ; Naumann, B. ; Boehm, A.V. ; Gnecco, E. ; Bonse, Jörn ; Neumann, C. ; Turchanin, A. ; Müller, F.A. ; Gräf, S.
The formation and properties of laser-induced periodic surface structures (LIPSS) were investigated on carbon fibers under irradiation of fs-laser pulses characterized by a pulse duration τ = 300 fs and a laser wavelength λ = 1025 nm. The LIPSS were fabricated in an air environment at normal incidence with different values of the laser peak fluence and number of pulses per spot. The morphology of the generated structures was characterized by using scanning electron microscopy, atomic force microscopy and Fast-Fourier transform analyses. Moreover, the material structure and the surface chemistry of the carbon fibers before and after laser irradiation was analyzed by micro Raman spectroscopy and X-ray photoelectron spectroscopy. Large areas in the cm2 range of carbon fiber arrangements were successfully processed with homogenously distributed high- and low-spatial frequency LIPSS. Beyond those distinct nanostructures, hybrid structures were realized for the very first time by a superposition of both types of LIPSS in a two-step process. The findings facilitate the fabrication of tailored LIPSS-based surface structures on carbon fibers that could be of particular interest for e.g. fiber reinforced polymers and concretes.
Quo vadis LIPSS? – Recent developments in theoretical modelling and technical applications (2019)
Bonse, Jörn
This presentation reviews current and expected developments in the field of laser-induced periodic surface structures (LIPSS, ripples). These surface nanostructures are a universal phenomenon and can be generated on almost any material by irradiation with intense linearly polarized radiation. LIPSS are formed in a “self-ordered” way and are often accompanying laser material processing applications. The structures can be produced in a single-step process and enable surface functionalization through the adaption of optical, mechanical and chemical surface properties. Their spatial periods typically range from several micrometers down to less than 100 nanometers, exhibiting a clear correlation with the polarization direction of the laser radiation used. Various types of LIPSS have been classified, relevant control parameters were identified, and material specific formation mechanisms are analyzed for different types of inorganic solids, i.e., metals, semiconductors, and dielectrics, through time-resolved optical experiments and theoretical simulations. Special attention will be paid to a comparison of the currently available formation theories for LIPSS with a discussion of their respective strengths and weaknesses. Currrently explored applications featuring surface functionalization in the fields of optics, surface wetting, medicine, and tribology will be discussed.
Emission von Röntgenstrahlung bei der UKP-Laser-Materialbearbeitung (2019)
Bonse, Jörn
Der Vortrag stellt Untersuchungen im Rahmen eines BMBF-geförderten Vorhabens zur unerwünschten Emission von Röntgenstahlung bei der Materialbearbeitung mit ultrakurzen Laserpulsen vor.
Fabrication of regularly arranged chalcopyrite micro solar cells via femtosecond laser-induced forward transfer for concentrator application (2018)
Heidmann, B. ; Andree, Stefan ; Levcenko, S. ; Unold, T. ; Abou-Ras, D. ; Schäfer, N. ; Bonse, Jörn ; Krüger, Jörg ; Schmid, M.
A laser-based bottom-up technique for the fabrication of Cu(In,Ga)Se2 (CIGSe) micro solar cells is presented. We use femtosecond laser-induced forward transfer (LIFT) to transport a metallic precursor composed of copper, indium, and gallium onto a molybdenum back contact layer on a glass substrate. A CIGSe absorber forms by subsequent selenization. An array of micro absorbers with defined spacing is fabricated to solar cells and characterized under concentrated light illumination. The solar cell array exhibited a conversion efficiency of 1.4‰ at 1 sun as well as a significant efficiency enhancement of 68% rel. under 20-fold concentration. This work demonstrates the possibility of directly grown micrometer-sized solar cells based on chalcogenide absorber layers, enabling effective material usage.
Influence of femtosecond laser produced nanostructures on biofilm growth on steel (2017)
Epperlein, Nadja ; Menzel, Friederike ; Schwibbert, Karin ; Koter, Robert ; Bonse, Jörn ; Sameith, Janin ; Krüger, Jörg ; Toepel, Jörg
Biofilm formation poses high risks in multiple industrial and medical settings. However, the robust nature of biofilms makes them also attractive for industrial applications where cell biocatalysts are increasingly in use. Since tailoring material properties that affect bacterial growth or its inhibition is gaining attention, here we focus on the effects of femtosecond laser produced nanostructures on bacterial adhesion. Large area periodic surface structures were generated on steel surfaces using 30-fs laser pulses at 790 nm wavelength. Two types of steel exhibiting a different corrosion resistance were used, i.e., a plain structural steel (corrodible) and a stainless steel (resistant to corrosion). Homogeneous fields of laser-induced periodic surface structures (LIPSS) were realized utilizing laser fluences close to the ablation threshold while scanning the sample under the focused laser beam in a multi-pulse regime. The nanostructures were characterized with optical and scanning electron microscopy. For each type of steel, more than ten identical samples were laser-processed. Subsequently, the samples were subjected to microbial adhesion tests. Bacteria of different shape and adhesion behavior (Escherichia coli and Staphylococcus aureus) were exposed to laser structures and to polished reference surfaces. Our results indicate that E. coli preferentially avoids adhesion to the LIPSS-covered areas, whereas S. aureus favors these areas for colonization.
Dynamics of ultrashort double-pulse laser ablation of solid surfaces (2017)
Rosenfeld, A. ; Höhm, S. ; Krüger, Jörg ; Bonse, Jörn
Given their unique properties, ultrashort laser pulses with durations in the femtosecond to picosecond range currently open new avenues in the field of laser materials processing, resulting in groundbreaking new applications based on laser-induced surface functionalization. This article reviews the usability of temporally distributed energy deposition via double-pulse irradiation in applications based on laser ablation. This includes simple new techniques for surface nanostructuring and improved sensitivities in spectroscopic material analyses.
Excitation and relaxation dynamics in ultrafast laser irradiated optical glasses (2016)
Mauclair, C. ; Mermillod-Blondin, A. ; Mishchik, K. ; Bonse, Jörn ; Rosenfeld, A. ; Colombier, J. P. ; Stoian, R.
We discuss the dynamics of ultrashort pulsed laser excitation in bulk optical silica-based glasses (fused silica and borosilicate BK7) well-above the permanent modification threshold. We indicate subsequent structural and thermomechanical energy relaxation paths that translate into positive and negative refractive index changes, compression and rarefaction zones. If fast electronic decay occurs at low excitation levels in fused silica via self-trapping of excitons, for carrier densities in the vicinity of the critical value at the incident wavelength, persistent long-living absorptive states indicate the achievement of low viscosity matter states manifesting pressure relaxation, rarefaction, void opening and compaction in the neighboring domains. An intermediate ps-long excited carrier dynamics is observed for BK7 in the range corresponding to structural expansion and rarefaction. The amount of excitation and the strength of the subsequent hydrodynamic evolution is critically dependent on the pulse time envelope, indicative of potential optimization schemes.
  • 1 bis 10

OPUS4 Logo

  • Kontakt
  • Impressum
  • Sitelinks