TY - CONF A1 - Bonse, Jörn A1 - Höhm, S. A1 - Kirner, Sabrina A1 - Rosenfeld, A. A1 - Krüger, Jörg T1 - Laser-induced periodic surface structures (LIPSS) - A scientific evergreen T2 - OSA Technical Digest (2016) N2 - The current state in the field of laser-induced periodic surface structures (LIPSS, ripples) is reviewed. Their formation mechanisms are analyzed in ultrafast experiments (time-resolved diffraction and polarization controlled double-pulse experiments) and technological applications are demonstrated. T2 - Conference on Lasers and Electro-Optics (CLEO) - Science and Innovations 2016 CY - San Jose, CA, USA DA - 05.06.2016 KW - Laser materials processing KW - Optics at surfaces KW - Ultrafast phenomena KW - Laser-induced periodic surface strcutures (LIPSS) KW - Femtosecond laser ablation PY - 2016 SN - 978-1-943580-11-8 DO - https://doi.org/10.1364/CLEO_SI.2016.STh1Q.3 SP - STh1Q.3, 1 EP - 2 PB - Optical Society of America AN - OPUS4-37072 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krüger, Jörg A1 - Mann, Guido T1 - Nanosecond laser damage of optical multimode fibers N2 - For pulse laser materials processing often optical step index and gradient index multimode fibers with core diameters ranging from 100 to 600 μm are used. The design of a high power fiber transmission system must take into account limitations resulting from both surface and volume damage effects. Especially, breakdown at the fiber end faces and self-focusing in the fiber volume critically influence the fiber performance. At least operation charts are desirable to select the appropriate fiber type for given laser parameters. In industry-relevant studies the influence of fiber core diameter and end face preparation on laser-induced (surface) damage thresholds (LIDT) was investigated for frequently used all-silica fiber types (manufacturer LEONI). Experiments on preform material (initial fiber material) and compact specimens (models of the cladding and coating material) accompanied the tests performed in accordance with the relevant LIDT standards ISO 11254-1 and ISO 11254-2 for 1-on-1 and S-on-1 illumination conditions, respectively. The relation beam diameter vs. LIDT was investigated for fused silica fibers and preforms. Additionally, the laser-induced (bulk) damage threshold of fused silica preform material F300 (manufacturer Heraeus) in dependence on external mechanical stress simulating fiber bending was measured. All experiments were performed with 10-ns laser pulses at 1064 and 532 nm wavelength with a Gaussian beam profile. T2 - Pacific Rim Laser Damage Conference CY - Yokohama, Japan DA - 18.05.2016 KW - Laser induced damage KW - Optical multimode fiber KW - Nd:YAG laser KW - Nanosecond Pulses PY - 2016 AN - OPUS4-36258 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krüger, Jörg T1 - Herausforderungen der Femtosekunden-Technologie an den Laserschutz N2 - Die Verleihung des Deutschen Zukunftspreises an ein Team zum Thema "Ultrakurzpulslaser für die industrielle Massenfertigung - Produzieren mit Lichtblitzen" im Jahr 2013 belegt die industrielle Relevanz des Ultrakurzpulslasereinsatzes in der Materialbearbeitung. Zunehmend werden weitere Anwendungen z.B. in der Mess- und Medizintechnik erschlossen. Femtosekunden-Laserpulse weisen prinzipbedingt ein breites Spektrum auf und besitzen bereits bei moderaten Pulsenergien extreme Pulsspitzenleistungen, womit über „konventionelle“ Laserquellen hinausgehende Herausforderungen an den Laserschutz entstehen. Die in entsprechenden Laserschutzbrillen verwendeten Laserschutzfilter müssen eine große spektrale Absorptionsbandbreite aufweisen und dürfen nicht aufschalten, d.h. keine induzierte Transmission zeigen. Im Vortrag soll dargestellt werden, dass Laserschutzfilter auf Glasbasis, die über ein breites Absorptionsspektrum verfügen, einen ausreichenden Schutz gegenüber fs-Laserstrahlung bieten, wohingegen Laserschutzfilter auf Polymerbasis eine induzierte spektrale Transmission bei steigender Energiedichte aufweisen können, was zu einem drastischen Verlust der Schutzfunktion führt. T2 - Symposium Strahlenschutz – Neue Technologien im Laserschutz CY - BIZBw, Mannheim, Germany DA - 17.11.2015 KW - Laserschutz KW - Schutzbrille KW - Ultrakurzpulslaser KW - Glasfilter KW - Polymerfilter PY - 2015 AN - OPUS4-36259 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Symietz, Christian A1 - Krüger, Jörg ED - Vilar, Rui T1 - Stability of laser surface modified implants T2 - Laser Surface Modification of Biomaterials: Techniques and applications N2 - A new technique to fix bioceramic powder on a titanium alloy by using femtosecond laser pulses is presented. It is shown that gentle fixation of a bioactive dielectric material on a metallic model implant is successful. This is potentially a new tool for the improvement of bone prostheses. An advantage of the ultrashort pulses is the very low heat influx into the whole sample. There is only a very thin interaction zone during the fixing, which is the metal surface in contact with the ceramic layer. Neither the fixed ceramic particles nor the major part of the metal suffer any modification. The stability of the model implant (ceramic on metal) is investigated by rotating bending fatigue tests. No indication of a reduction of the mechanical stability compared to untreated metallic reference samples was found. KW - Bone implant KW - Calcium phosphate coating KW - Femtosecond laser KW - Laser-induced fixation KW - Titanium alloy PY - 2016 SN - 978-0-08-100883-6 SN - 978-0-08-100942-0 DO - https://doi.org/10.1016/B978-0-08-100883-6.00004-6 SN - 2049-9485 IS - 111 SP - Chapter 4, 127 EP - 143 PB - Elsevier ET - 1st edition AN - OPUS4-36790 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Derrien, Thibault A1 - Koter, Robert A1 - Krüger, Jörg A1 - Höhm, S. A1 - Rosenfeld, A. A1 - Bonse, Jörn T1 - Plasmonic formation mechanism of periodic 100-nm-structures upon femtosecond laser irradiation of silicon in water JF - Journal of applied physics N2 - The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of 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. The LIPSS surface morphologies are characterized by scanning electron microscopy and their spatial periods are quantified by two-dimensional Fourier analyses. It is demonstrated that the irradiation environment significantly influences the periodicity of the LIPSS. In air, so-called low-spatial frequency LIPSS (LSFL) were found with periods somewhat smaller than the laser wavelength (ΛLSFL ~ 0.7 × λ0) and an orientation perpendicular to the laser polarization. In contrast, for laser processing in water a reduced ablation threshold and LIPSS with approximately five times smaller periods ΛLIPSS ~ 0.15 × λ0 were observed in the same direction as in air. The results are discussed within the frame of recent LIPSS theories and complemented by a thin film based surface plasmon polariton model, which successfully describes the tremendously reduced LIPSS periods in water. PY - 2014 DO - https://doi.org/10.1063/1.4887808 SN - 0021-8979 SN - 1089-7550 VL - 116 IS - 7 SP - 074902-1 EP - 074902-8 PB - American Institute of Physics CY - Melville, NY AN - OPUS4-31209 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krüger, Jörg T1 - Ultrakurze Laserpulse für technische und biomedizinische Applikationen T2 - Workshop "Brillante Diodenlaser für neue Anwendungen in der Lasermaterialbearbeitung" T2 - Workshop "Brillante Diodenlaser für neue Anwendungen in der Lasermaterialbearbeitung" CY - Berlin, Germany DA - 2014-03-18 PY - 2014 AN - OPUS4-30579 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Koter, Robert A1 - Hartelt, Manfred A1 - Spaltmann, Dirk A1 - Pentzien, Simone A1 - Höhm, S. A1 - Rosenfeld, A. A1 - Krüger, Jörg T1 - Femtosecond laser-induced periodic surface structures on steel and titanium alloy for tribological applications JF - Applied physics A N2 - Laser-induced periodic surface structures (LIPSS, ripples) were generated on stainless steel (100Cr6) and titanium alloy (Ti6Al4V) surfaces upon irradiation with multiple femtosecond laser pulses (pulse duration 30 fs, central wavelength 790 nm). The experimental conditions (laser fluence, spatial spot overlap) were optimized in a sample-scanning geometry for the processing of large surface areas (5 × 5 mm²) covered homogeneously by the nanostructures. The irradiated surface regions were subjected to white light interference microscopy and scanning electron microscopy revealing spatial periods around 600 nm. The tribological performance of the nanostructured surface was characterized by reciprocal sliding against a ball of hardened steel in paraffin oil and in commercial engine oil as lubricants, followed by subsequent inspection of the wear tracks. For specific conditions, on the titanium alloy a significant reduction of the friction coefficient by a factor of more than two was observed on the laser-irradiated (LIPSS-covered) surface when compared to the non-irradiated one, indicating the potential benefit of laser surface structuring for tribological applications. PY - 2014 DO - https://doi.org/10.1007/s00339-014-8229-2 SN - 0947-8396 VL - 117 IS - 1 SP - 103 EP - 110 PB - Springer CY - Berlin AN - OPUS4-31450 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Derrien, Thibault A1 - Krüger, Jörg A1 - Itina, T.E. A1 - Höhm, S. A1 - Rosenfeld, A. A1 - Bonse, Jörn T1 - Rippled area formed by surface plasmon polaritons upon femtosecond laser double-pulse irradiation of silicon: the role of carrier generation and relaxation processes JF - Applied physics A N2 - The formation of laser-induced periodic surface structures (LIPSS, ripples) upon irradiation of silicon with multiple irradiation sequences consisting of femtosecond laser pulse pairs (pulse duration 150 fs, central wavelength 800 nm) is studied numerically using a rate equation system along with a two-temperature model accounting for one- and two-photon absorption and subsequent carrier diffusion and Auger recombination processes. The temporal delay between the individual equal-energy fs-laser pulses was varied between 0 and ~4 ps for quantification of the transient carrier densities in the conduction band of the laser-excited silicon. The results of the numerical analysis reveal the importance of carrier generation and relaxation processes in fs-LIPSS formation on silicon and quantitatively explain the two time constants of the delay-dependent decrease of the low spatial frequency LIPSS (LSFL) area observed experimentally. The role of carrier generation, diffusion and recombination is quantified individually. PY - 2014 DO - https://doi.org/10.1007/s00339-013-8205-2 SN - 0947-8396 VL - 117 IS - 1 SP - 77 EP - 81 PB - Springer CY - Berlin AN - OPUS4-31451 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krüger, Jörg T1 - Laserreinigung von Kunst- und Kulturgut am Beispiel organischer Materialien T2 - Innovationsforum Inn-O-Kultur T2 - Innovationsforum Inn-O-Kultur CY - Erfurt, Germany DA - 2014-07-14 PY - 2014 AN - OPUS4-31113 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mann, Guido A1 - Vogel, Jens A1 - Zoheidi, M. A1 - Eberstein, Markus A1 - Krüger, Jörg T1 - Breakdown limits of optical multimode fibers for the application of nanosecond laser pulses at 532 nm and 1064 nm wavelength JF - Applied surface science N2 - For many applications, optical multimode fibers are used for the transmission of powerful laser radiation. High light throughput and damage resistance are desirable. Laser-induced breakdown at the end faces of fibers can limit their performance. Therefore, the determination of laser-induced damage thresholds (LIDT) at the surface of fibers is essential. Nanosecond (1064 nm and 532 nm wavelength) single-shot LIDT were measured according to the relevant standard on SiO2 glass preforms (Suprasil F300) as basic materials of the corresponding fibers. For 10 kinds of fused silica fibers (FiberTech) with core diameters between 180 µm and 600 µm, an illumination approach utilizing a stepwise increase of the laser fluence on a single spot was used. For both wavelengths, the LIDT values (0% damage probability) obtained by means of the two methods were compared. The influence of surface preparation (polishing) on damage resistance was investigated. For equal surface finishing, a correlation between drawing speed of the fibers and their surface LIDT values was found. In addition to the surface measurements, bulk LIDT were determined for the preform material. KW - Fiber waveguides KW - Physical radiation damage KW - Laser-beam impact phenomena KW - Glasses KW - Radiation treatment PY - 2009 DO - https://doi.org/10.1016/j.apsusc.2008.07.157 SN - 0169-4332 SN - 1873-5584 VL - 255 IS - 10 SP - 5519 EP - 5522 PB - North-Holland CY - Amsterdam AN - OPUS4-19036 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krüger, Jörg A1 - Pentzien, Simone A1 - Pucko Mencigar, D. A1 - Strilic, M. T1 - The influence of paper type and state of degradation on laser cleaning of artifically soiled paper T2 - Konferenz LACONA 8 T2 - Konferenz LACONA 8 CY - Sibiu, Romania DA - 2009-09-21 PY - 2009 AN - OPUS4-19288 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Holle, H. A1 - Kautek, W. A1 - Pentzien, Simone A1 - Krüger, Jörg A1 - Mäder, M. A1 - Schreiner, M. T1 - Laser cleaning on historic picture postcards T2 - Research in book and paper conservation in Europe - a state of the art N2 - This contribution compares traditional cleaning and laser methods. Partial laser cleaning with a nanosecond pulse laser (wavelength of 532 nm) has proved very promising for future application in paper conservation-restoration. Traditional cleaning methods are not always sufficient or successful in surface cleaning of objects of art. Comparative studies of traditional paper cleaning methods and laser cleaning were made on several historic picture postcards printed with the chromolithography technique. PY - 2009 SN - 978-3-85028-490-5 SP - 189 EP - 206 PB - Berger Horn CY - Wien, Austria AN - OPUS4-20397 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Pentzien, Simone A1 - Conradi, Andrea A1 - Lussky, K. A1 - Engel, P. A1 - Krüger, Jörg ED - Engel, Patricia T1 - Laser cleaning of artificially soiled paper T2 - Research in book and paper conservation in Europe - a state of the art N2 - Laser cleaning for works of art on paper might be a supplemental, noncontact method to overcome some of the limitations of traditional dry cleaning techniques. Three different types of paper (pure-cellulose filter paper, rag paper, and wood-pulp paper) were mechanically soiled with pulverized charcoal in a standardized procedure to make model samples. These samples were characterized microscopically and by means of lightness measurements using a multi-spectral imaging system. A prototype laser workstation with Laser Class I conditions for the operator was used for the cleaning experiments. For 10-ns laser pulses at a wavelength of 532 nm, a set of laser parameters was established for a successful cleaning of the samples avoiding damage to the paper substrate. Single- and multi-pulse illumination conditions were tested. An extensive microscopic analysis after laser treatment of the cleaned parts of the samples provided insight into the remaining soiling on the surface and in the bulk of the paper material. PY - 2009 SN - 978-3-85028-490-5 SP - 171 EP - 188 PB - Berger Horn CY - Wien, Austria AN - OPUS4-20398 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mann, Guido A1 - Jurke, Mathias A1 - Zoheidi, M. A1 - Eberstein, Markus A1 - Krüger, Jörg T1 - Influence of core diameter and coating material on nanosecond laser-induced damage threshold of optical multimode fibers JF - Journal of optoelectronics and advanced materials N2 - Single and multi pulse laser-induced damage thresholds (LIDT) of core, cladding, and coating materials of high-power optical multimode fibers were determined in accordance with ISO 11254 for 532 nm and 1064 nm wavelength in the 10-ns pulse duration regime with spatial Gaussian beam shape. For all-silica fibers, LIDT increases with rising core diameter in a range between 100-600 µm for a constant cladding-core ratio of 1.2. The damage resistance of the low refracting cladding (0.3 % fluorine doped fused silica) is comparable to the undoped SiO2 core. Coating materials show significantly lower LIDT than light-guiding parts of the fibers. KW - Fiber waveguides (42.81.Qb) KW - Physical radiation damage (61.80.-x) KW - Laser-beam impact phenomena (79.20.Ds) KW - Glasses (81.05.Kf) PY - 2010 SN - 1454-4164 VL - 12 IS - 3 SP - 711 EP - 714 PB - INOE & INFM CY - Bucharest AN - OPUS4-21083 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Koter, Robert A1 - Weise, Matthias A1 - Hertwig, Andreas A1 - Beck, Uwe A1 - Krüger, Jörg T1 - Influence of film thickness and optical constants on femtosecond laser-induced ablation of hydrogenated amorphous carbon films JF - Journal of optoelectronics and advanced materials N2 - Hydrogenated amorphous carbon layers were deposited on BK7 glass in a plasma-assisted chemical vapor deposition process. Low and high refracting films with thicknesses d ranging from 11 nm to 5.8 µm were produced having refractive indices n between 1.68 and 2.41 and linear absorption coefficients of α~100 cm-1 and α~20000 cm-1 at 800 nm wavelength as a result of different plasma modes. Laser ablation thresholds Fth in dependence on d were determined using 30-fs laser pulses. Low absorbing layers show a constant Fth while Fth increases with rising d up to the optical penetration depth of light α-1 for high absorbing films. KW - Physical radiation damage (61.80.-x) KW - Laser-beam impact phenomena (79.20.Ds) KW - Radiation treatment (81.40.Wx) KW - Carbon (81.05.Uw) KW - Optical constants (78.20.Ci) PY - 2010 SN - 1454-4164 VL - 12 IS - 3 SP - 663 EP - 667 PB - INOE & INFM CY - Bucharest AN - OPUS4-21084 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Symietz, Christian A1 - Lehmann, Erhard A1 - Gildenhaar, Renate A1 - Krüger, Jörg A1 - Berger, Georg T1 - Femtosecond laser induced fixation of calcium alkali phosphate ceramics on titanium alloy bone implant material JF - Acta biomaterialia N2 - Femtosecond lasers provide a novel method of attaching bioceramic material to a titanium alloy, thereby improving the quality of bone implants. The ultrashort 30 fs laser pulses (790 nm wavelength) penetrate a thin dip-coated layer of fine ceramic powder, while simultaneously melting a surface layer of the underlying metal. The specific adjustment of the laser parameters (pulse energy and number of pulses per spot) avoids unnecessary melting of the bioactive calcium phosphate, and permits a defined thin surface melting of the metal, which in turn is not heated throughout, and therefore maintains its mechanical stability. It is essential to choose laser energy densities that correspond to the interval between the ablation fluences of both materials involved: about 0.1-0.4 J cm-2. In this work, we present the first results of this unusual technique, including laser ablation studies, scanning electron microscopy and optical microscope images, combined with EDX data. KW - Bone implant KW - Bioceramic coating KW - Titanium KW - Calcium phosphate KW - Femtosecond laser PY - 2010 DO - https://doi.org/10.1016/j.actbio.2010.02.016 SN - 1742-7061 VL - 6 IS - 8 SP - 3318 EP - 3324 PB - Elsevier CY - Amsterdam AN - OPUS4-21446 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Krüger, Jörg A1 - Symietz, Christian A1 - Lehmann, Erhard A1 - Gildenhaar, Renate A1 - Koter, Robert A1 - Berger, Georg T1 - The production of metallic implant materials with a bioactive ceramic layer using femtosecond laser pluses T2 - ISL 2010 - 3rd International Symposium on Laser-Micromachining T2 - ISL 2010 - 3rd International Symposium on Laser-Micromachining CY - Chemnitz, Germany DA - 2010-10-27 PY - 2010 AN - OPUS4-21901 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bonse, Jörn A1 - Rosenfeld, A. A1 - Krüger, Jörg T1 - Implications of transient changes of optical and surface properties of solids during femtosecond laser pulse irradiation to the formation of laser-induced periodic surface structures JF - Applied surface science N2 - The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of silicon wafer surfaces by linearly polarized Ti:sapphire femtosecond laser pulses (pulse duration 130 fs, central wavelength 800 nm) is studied experimentally and theoretically. In the experiments, so-called low-spatial frequency LIPSS (LSFL) were found with periods smaller than the laser wavelength and an orientation perpendicular to the polarization. The experimental results are analyzed by means of a new theoretical approach, which combines the widely accepted LIPSS theory of Sipe et al. with a Drude model, in order to account for transient (intra-pulse) changes of the optical properties of the irradiated materials. It is found that the LSFL formation is caused by the excitation of surface plasmon polaritons, SPPs, once the initially semiconducting material turns to a metallic state upon formation of a dense free-electron-plasma in the material and the subsequent interference between its electrical field with that of the incident laser beam resulting in a spatially modulated energy deposition at the surface. Moreover, the influence of the laser-excited carrier density and the role of the feedback upon the multi-pulse irradiation and its relation to the excitation of SPP in a grating-like surface structure is discussed. KW - Femtosecond laser ablation KW - Laser-induced periodic surface structures KW - (LIPSS) KW - Optical properties KW - Surface plasmon polaritons KW - Semiconductors KW - Silicon PY - 2011 DO - https://doi.org/10.1016/j.apsusc.2010.11.059 SN - 0169-4332 SN - 1873-5584 VL - 257 IS - 12 SP - 5420 EP - 5423 PB - Elsevier B.V. CY - Amsterdam AN - OPUS4-23309 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Symietz, Christian A1 - Lehmann, Erhard A1 - Gildenhaar, Renate A1 - Koter, Robert A1 - Berger, Georg A1 - Krüger, Jörg T1 - Fixation of bioactive calcium alkali phosphate on Ti6Al4V implant material with femtosecond laser pulses JF - Applied surface science N2 - Bone implants made of metal, often titanium or the titanium alloy Ti6Al4V, need to be surface treated to become bioactive. This enables the formation of a firm and durable connection of the prosthesis with the living bone. We present a new method to uniformly cover Ti6Al4V with a thin layer of ceramics that imitates bone material. These calcium alkali phosphates, called GB14 and Ca10, are applied to the metal by dip coating of metal plates into an aqueous slurry containing the fine ceramic powder. The dried samples are illuminated with the 790 nm radiation of a pulsed femtosecond laser. If the laser fluence is set to a value just below the ablation threshold of the ceramic (ca. 0.4 J/cm²) the 30 fs laser pulses penetrate the partly transparent ceramic layer of 20–40 µm thickness. The remaining laser fluence at the ceramic–metal interface is still high enough to generate a thin metal melt layer leading to the ceramic fixation on the metal. The laser processing step is only possible because Ti6Al4V has a lower ablation threshold (between 0.1 and 0.15 J/cm²) than the ceramic material. After laser treatment in a fluence range between 0.1 and 0.4 J/cm², only the particles in contact with the metal withstand a post-laser treatment (ultrasonic cleaning). The non-irradiated rest of the layer is washed off. In this work, we present results of a successful ceramic fixation extending over larger areas. This is fundamental for future applications of arbitrarily shaped implants. KW - Bone implant KW - Bioceramic coating KW - Titanium KW - Calcium phosphate KW - Femtosecond laser PY - 2011 DO - https://doi.org/10.1016/j.apsusc.2010.10.046 SN - 0169-4332 SN - 1873-5584 VL - 257 IS - 12 SP - 5208 EP - 5212 PB - North-Holland CY - Amsterdam AN - OPUS4-23310 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Bonse, Jörn A1 - Rosenfeld, A. A1 - Krüger, Jörg ED - Panchenko, V. ED - Mourou, G. ED - Zheltikov, A. M. T1 - Femtosecond laser-induced periodic surface structures: recent approaches to explain their sub-wavelength periodicities T2 - LAT 2010 - International Conference on Lasers, Applications, and Technologies (Proceedings of SPIE) N2 - The formation of laser-induced periodic surface structures (LIPSS) upon irradiation of semiconductors and dielectrics by linearly polarized high-intensity Ti:sapphire fs-laser pulses (τ ~100 fs, λ ~800 nm) is studied experimentally and theoretically. In the experiments, two different types of LIPSS exhibiting very different spatial periods are observed (socalled LSFL – low spatial frequency LIPSS, and HSFL - high spatial frequency LIPSS), both having a different dependence on the incident laser fluence and pulse number per spot. The experimental results are analyzed by means of a new theoretical approach, which combines the generally accepted LIPSS theory of J. E. Sipe and co-workers [Phys. Rev. B 27, 1141-1154 (1983)] with a Drude model, in order to account for transient changes of the optical properties of the irradiated materials. The joint Sipe-Drude model is capable of explaining numerous aspects of fs-LIPSS formation, i.e., the orientation of the LIPSS, their fluence dependence as well as their spatial periods. The latter aspect is specifically demonstrated for silicon crystals, which show experimental LSFL periods Λ somewhat smaller than λ. This behaviour is caused by the excitation of surface plasmon polaritons, SPP, (once the initially semiconducting material turns to a metallic state upon formation of a dense free-electron-plasma in the material) and the subsequent interference between its electrical fields with that of the incident laser beam, resulting in a spatially modulated energy deposition at the surface. Upon multi-pulse irradiation, a feedback mechanism, caused by the redshift of the resonance in a grating-assisted SPP excitation, is further reducing the LSFL spatial periods. The SPP-based mechanism of LSFL successfully explains the remarkably large range of LSFL periods between ~0.6 λ and λ. T2 - LAT 2010 - International Conference on Lasers, Applications, and Technologies CY - Kazan, Russia DA - 23.08.2010 KW - Femtosecond laser ablation KW - Laser-induced periodic surface structures (LIPSS) KW - Surface plasmon polaritons KW - Second harmonic generation (SHG) KW - Silicon KW - Semiconductors KW - Dielectrics PY - 2011 DO - https://doi.org/10.1117/12.879813 SN - 0277-786X N1 - Serientitel: Proceedings of SPIE – Series title: Proceedings of SPIE VL - 7994 SP - 79940M-1 EP - 79940M-10 CY - Bellingham, USA AN - OPUS4-23291 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -