We industrialized the functionalization of metal surfaces with LIPSS using beam shaping technique... more We industrialized the functionalization of metal surfaces with LIPSS using beam shaping techniques, for application on two and three-dimensional medical implants. Osteoblasts adhered and mineralized favorably and controllably onto the produced surfaces.
Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXIII, 2018
The today available ultra-short pulsed laser systems offer average power in the range of 100 W or... more The today available ultra-short pulsed laser systems offer average power in the range of 100 W or even more resulting in high pulse energies. In contrast to treat metals only moderate peak fluences are required to work at the well-known optimum point, where the ablation process is most energy efficient. In a standard setup the laser beam is deflected by a galvo scanner. The achievable scan speed is limited and therefore also the usable repetition frequency and average power. The use of pulse bursts instead of single pulses is a possibility to further increase the ablation rate, i.e. using higher average power. This further increase is crucial for the usage of the ultra-short pulses in industrial applications. It was shown in previous publications that the number of pulses in the burst have a significant influence on the specific removal rate in case of ps pulses. It was observed, that the second pulse of a 2-pulse burst is shielded by the particle plume of the first pulse of the burst. It is believed that the shielding effect depends on the particle density of the plume, thus the effect should be stronger if more material is ablated. As already known, a decrease of the pulse duration to a few hundreds of fs leads to an increase of the specific removal rate for single pulses. In this work we investigate the influence of pulse bursts on the specific removal rate as well as the pulse duration on the ablation process using pulse bursts.
The uniform energy distribution of top-hat laser beams is a very attractive property that can off... more The uniform energy distribution of top-hat laser beams is a very attractive property that can offer some advantages compared to Gaussian beams. Especially, the desired intensity distribution can be achieved at the laser spot through energy redistribution across the beam spatial profile and, thus, to minimize and even eliminate some inherent shortcomings in laser micro-processing. This paper reports an empirical study that investigates the effects of top-hat beam processing in micro-structuring and compares the results with those obtainable with a conventional Gaussian beam. In particular, a refractive field mapping beam shaper was used to obtain a top-hat profile and the effects of different scanning strategies, pulse energy settings, and accumulated fluence, i.e., hatch and pulse distances, were investigated. In general, the top-hat laser processing led to improvements in surface and structuring quality. Especially, the taper angle was reduced while the surface roughness and edge d...
We investigate the processing times of ultrafast laser machining in the case of metals (copper an... more We investigate the processing times of ultrafast laser machining in the case of metals (copper and stainless steel). At a fluence of 2.5 J/cm 2 , measurements of processing times are in good agreement with the calculations based on the ablation rates. We study the influence of laser repetition rates for 1, 5, 10 and 15 kHz. A linear reduction of the processing time can be expected with an increase of the repetition rate.
Studies on corneal surgery and flap processing on enucleated porcine eyes have been performed usi... more Studies on corneal surgery and flap processing on enucleated porcine eyes have been performed using a dedicated 100 kHz femtosecond laser source based on Ytterbium technology. IR (1035 nm) and green (517 nm) flap processing have been studied. Comparisons for ocular femtosecond laser surgery are discussed in terms of process efficiency and safety aspects. Flaps with a typical diameter of 6 mm and 150 mum thick have been performed in less than 2 min with both wavelengths. The transmittances of femtosecond laser pulses through the ocular media of porcine eyes have been measured for a collimated beam and during flap processing. More than 25% of energy is transmitted through the whole eye at the retina during IR pulses flap processing. Concerning green pulses, if less energy is necessary to perform the flap which is of prime interest, the transmission of green light is very high and could be an undeniable obstacle for the safety.
A high accurate, compact and flexible laser nanoprocessing and large area mapping with high-resol... more A high accurate, compact and flexible laser nanoprocessing and large area mapping with high-resolution apparatus is presented in this paper. Judicious hardware and software developments of the device are presented, which allow a high range of applications and performances. Coupled to a low average and low cost femtosecond laser system, results on accurate nanoprocessing on biological and biotechnological samples demonstrate the potential of the machine. Nanostructuring of different type of materials with this device is conceivable for a wide spectrum of technological applications in material science, nanobiotechnology and nanomedicine.
Preventing and reducing the impact of counterfeiting activities are among the most important preo... more Preventing and reducing the impact of counterfeiting activities are among the most important preoccupations for modern companies to preserve and protect the value of their work. Some technologies use LASER marking to code information in 2D, directly on material surface. In this work, deep marking of several materials is investigated. The purpose is to use the depth of a marked surface (for different materials : metals and dielectrics) as a third data storage axis. The idea is to convert a performed depth in a grey level in the reading procedure. This marking depth can be then used for coding. Best results are obtained with polymers when transmission lightening is used for reading.
Ultrafast laser micromachining results depend on both the processing parameters and the material ... more Ultrafast laser micromachining results depend on both the processing parameters and the material properties. The thermal effects are negligible if a good combination of processing parameters is chosen. However, optimizing the processing parameters to achieve the required surface quality on a given material can be quite complex and time consuming. Within the framework of the European LAMpAS project, we developed a model to estimate the heat accumulation on a surface as a function of the laser fluence, scanning speed and line pitch. The simulation results were correlated with experimental ones. The predictions of the model allow evaluation of the heat distribution on the surface, and optimize the ultrafast laser micromachining strategy, yielding negligible thermal damage.
Ablation by ultrafast lasers results from a series of complex nonlinear phenomena of absorption a... more Ablation by ultrafast lasers results from a series of complex nonlinear phenomena of absorption and transfer of energy that take place in the surfaces of materials upon irradiation. Provided that a good window of processing parameters is chosen, the resulting thermal effects are in general negligible, making ultrafast lasers excellent micromachining tools applicable to most types of materials. It is thus beneficial to understand how ablation is affected by the laser processing parameters and the material properties, in order to optimize the micromachining processes. We propose an engineering model to estimate the dimensions of ablation, taking into account on the one hand the material properties such as the ablation threshold, penetration depth and the refractive index and, on the other hand, the processing parameters namely the pulse energy and beam diameter, scanning speed, repetition rate and angle of incidence. The model considers as well the effects of incubation, changes of topography during multi-pulse irradiation, surface reflectivity and Gaussian beam diameter variation with the distance to the focal plane. The model is able to simulate the profiles of ablation surfaces produced by normal or tilted laser beam, either for spot, line and area processing. The results obtained are validated by comparison to the ones obtained experimentally. Both the model and the experiments focus on stainless steel. The predictions of the model also allow for the optimization of the micromachining process, both energy and time wise.
Le développement actuel de la technologie induit une constante nécessité d’obtenir des tailles de... more Le développement actuel de la technologie induit une constante nécessité d’obtenir des tailles de plus en plus petites pouvant descendre jusqu’à des dimensions micrométriques et sub -micrométriques. L’ablation laser, qui a le grand avantage d’un enlèvement de matière très précis, est un candidat prometteur. Dans cette thèse on démontre la faisabilité de tirer avantage des impulsions laser femtosecondes avec la matière pour la micro et nano structuration, et ceci en ayant développé une machine compacte de grande précision et flexibilité. Une approche théorique comparant les régimes d’interaction à haute et basse cadence est présentée. Des investigations de l’efficacité du temps de procédé aussi bien que l’effet de la cadence pendant l’ablation de métaux ont été effectuées. Le potentiel de l’outil multifonctionnel couplé avec un oscillateur laser femtoseconde à haute cadence est montré pour différentes applications en biotechnologie. Les résultats sur la cartographie d’une large zone ...
Interview with David Bruneel, laser engineer and working at the R&D department of LASEA. This Bel... more Interview with David Bruneel, laser engineer and working at the R&D department of LASEA. This Belgian company which specialises in the production of laser micromachining systems, is a partner of the H2020 project Laser4Surf. David Bruneel talked with the European Science Communication Institute (ESCI) about shaping metal surfaces with nanosized structures and the market potential for such surfaces.
The benefits of replacing space and energy consuming actuators and sensors with so-called “active... more The benefits of replacing space and energy consuming actuators and sensors with so-called “active” materials have been well known for decades. One such material, shape memory alloys (SMAs), inspire particularly novel applications because of their unmatched power density, high force output, and ability to be multifunctional – acting simultaneously as both actuator and sensor. Recently, improved material processing techniques by companies such as Dynalloy have enabled repeatable, low-cost production of small-diameter (<100 µm) SMA wires capable of being actuated with minimal power at rates faster than 1 Hz. Additionally, a multifunctional power controller has been developed at North Carolina State University to simultaneously control the heating power input to SMA wires while measuring their changing electrical resistance. Advances such as these have enabled new applications to be considered in academia, such as steerable catheters and guidewires for use inside the human body, ligh...
Enabling of continuous photomasking using a pulsed laser source and polygon scanners to achieve h... more Enabling of continuous photomasking using a pulsed laser source and polygon scanners to achieve high repetition rates and pulse energy, precise beam guiding and stable handling of the moving web with the applied photomask resist.
The advantages of the femtosecond laser for micromachining of materials have been widely demonstr... more The advantages of the femtosecond laser for micromachining of materials have been widely demonstrated allowing the laser micromachining to reach a level of accuracy in the micrometer range level. However, most of the current femtosecond laser micromachining applications are for flat surfaces, 2D or 2.5D, requiring different kinds of machining: drilling, cutting, and texturing, for more and more exotic materials. Biomedical implants are a part of those new objects requiring very high level of accuracy and surface finish, and for complex geometries: cylindrical or hemispherical shapes. LASEA has developed a system combining femtosecond laser with 7 simultaneously moving axes: 5 mechanical axes and 2 galvanometric axes. This combines the 3D micromachining offered by the 5 axes with the fast scanning. The laser parameters and strategies are controlled owing to laser specific developed functionalities. Another challenge to overcome is the research of laser parameters which is time and ma...
It has been thoroughly demonstrated in the past years that ultrafast lasers are excellent tools f... more It has been thoroughly demonstrated in the past years that ultrafast lasers are excellent tools for micromachining virtually all types of materials, provided that a good window of processing parameters is chosen so that the resulting thermal effects are negligible.The ablation topography resulting by irradiation with these lasers typically depend on several factors related both to the laser beam and the material characteristics. As a consequence, the search for the optimal processing parameters that lead to some required ablation dimensions on a given material can be time consuming.To enhance this parameters search, LASEA developed the application tool LS-Plume®, based on a numerical model that allows estimating the ablation profiles of scanned lines and areas, as well as drilled cavities. The processing parameters required to run the application are the pulse energy, beam waist at the focus, pulse repetition rate, scanning speed and beam tilting angle, whereas the characteristics o...
Le developpement actuel de la technologie induit une constante necessite d’obtenir des tailles de... more Le developpement actuel de la technologie induit une constante necessite d’obtenir des tailles de plus en plus petites pouvant descendre jusqu’a des dimensions micrometriques et sub -micrometriques. L’ablation laser, qui a le grand avantage d’un enlevement de matiere tres precis, est un candidat prometteur. Dans cette these on demontre la faisabilite de tirer avantage des impulsions laser femtosecondes avec la matiere pour la micro et nano structuration, et ceci en ayant developpe une machine compacte de grande precision et flexibilite. Une approche theorique comparant les regimes d’interaction a haute et basse cadence est presentee. Des investigations de l’efficacite du temps de procede aussi bien que l’effet de la cadence pendant l’ablation de metaux ont ete effectuees. Le potentiel de l’outil multifonctionnel couple avec un oscillateur laser femtoseconde a haute cadence est montre pour differentes applications en biotechnologie. Les resultats sur la cartographie d’une large zone ...
We report on high-quality high-throughput laser milling of silicon with a sub-ps laser delivering... more We report on high-quality high-throughput laser milling of silicon with a sub-ps laser delivering more than 1 kW of average laser power on the workpiece. In order to avoid heat accumulation effects, the processing strategy for high-quality laser milling was adapted to the available average power by using five-pulse bursts, a large beam diameter of 372 µm to limit the peak fluence per pulse to approximately 0.7 J / c m 2 , and a high feed rate of 24 m/s. As a result, smooth surfaces with a low roughness of S a ≤ 0.6 µ m were achieved up to the investigated milling depth of 313 µm while maintaining a high material removal rate of 230 m m 3 / min .
We industrialized the functionalization of metal surfaces with LIPSS using beam shaping technique... more We industrialized the functionalization of metal surfaces with LIPSS using beam shaping techniques, for application on two and three-dimensional medical implants. Osteoblasts adhered and mineralized favorably and controllably onto the produced surfaces.
Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XXIII, 2018
The today available ultra-short pulsed laser systems offer average power in the range of 100 W or... more The today available ultra-short pulsed laser systems offer average power in the range of 100 W or even more resulting in high pulse energies. In contrast to treat metals only moderate peak fluences are required to work at the well-known optimum point, where the ablation process is most energy efficient. In a standard setup the laser beam is deflected by a galvo scanner. The achievable scan speed is limited and therefore also the usable repetition frequency and average power. The use of pulse bursts instead of single pulses is a possibility to further increase the ablation rate, i.e. using higher average power. This further increase is crucial for the usage of the ultra-short pulses in industrial applications. It was shown in previous publications that the number of pulses in the burst have a significant influence on the specific removal rate in case of ps pulses. It was observed, that the second pulse of a 2-pulse burst is shielded by the particle plume of the first pulse of the burst. It is believed that the shielding effect depends on the particle density of the plume, thus the effect should be stronger if more material is ablated. As already known, a decrease of the pulse duration to a few hundreds of fs leads to an increase of the specific removal rate for single pulses. In this work we investigate the influence of pulse bursts on the specific removal rate as well as the pulse duration on the ablation process using pulse bursts.
The uniform energy distribution of top-hat laser beams is a very attractive property that can off... more The uniform energy distribution of top-hat laser beams is a very attractive property that can offer some advantages compared to Gaussian beams. Especially, the desired intensity distribution can be achieved at the laser spot through energy redistribution across the beam spatial profile and, thus, to minimize and even eliminate some inherent shortcomings in laser micro-processing. This paper reports an empirical study that investigates the effects of top-hat beam processing in micro-structuring and compares the results with those obtainable with a conventional Gaussian beam. In particular, a refractive field mapping beam shaper was used to obtain a top-hat profile and the effects of different scanning strategies, pulse energy settings, and accumulated fluence, i.e., hatch and pulse distances, were investigated. In general, the top-hat laser processing led to improvements in surface and structuring quality. Especially, the taper angle was reduced while the surface roughness and edge d...
We investigate the processing times of ultrafast laser machining in the case of metals (copper an... more We investigate the processing times of ultrafast laser machining in the case of metals (copper and stainless steel). At a fluence of 2.5 J/cm 2 , measurements of processing times are in good agreement with the calculations based on the ablation rates. We study the influence of laser repetition rates for 1, 5, 10 and 15 kHz. A linear reduction of the processing time can be expected with an increase of the repetition rate.
Studies on corneal surgery and flap processing on enucleated porcine eyes have been performed usi... more Studies on corneal surgery and flap processing on enucleated porcine eyes have been performed using a dedicated 100 kHz femtosecond laser source based on Ytterbium technology. IR (1035 nm) and green (517 nm) flap processing have been studied. Comparisons for ocular femtosecond laser surgery are discussed in terms of process efficiency and safety aspects. Flaps with a typical diameter of 6 mm and 150 mum thick have been performed in less than 2 min with both wavelengths. The transmittances of femtosecond laser pulses through the ocular media of porcine eyes have been measured for a collimated beam and during flap processing. More than 25% of energy is transmitted through the whole eye at the retina during IR pulses flap processing. Concerning green pulses, if less energy is necessary to perform the flap which is of prime interest, the transmission of green light is very high and could be an undeniable obstacle for the safety.
A high accurate, compact and flexible laser nanoprocessing and large area mapping with high-resol... more A high accurate, compact and flexible laser nanoprocessing and large area mapping with high-resolution apparatus is presented in this paper. Judicious hardware and software developments of the device are presented, which allow a high range of applications and performances. Coupled to a low average and low cost femtosecond laser system, results on accurate nanoprocessing on biological and biotechnological samples demonstrate the potential of the machine. Nanostructuring of different type of materials with this device is conceivable for a wide spectrum of technological applications in material science, nanobiotechnology and nanomedicine.
Preventing and reducing the impact of counterfeiting activities are among the most important preo... more Preventing and reducing the impact of counterfeiting activities are among the most important preoccupations for modern companies to preserve and protect the value of their work. Some technologies use LASER marking to code information in 2D, directly on material surface. In this work, deep marking of several materials is investigated. The purpose is to use the depth of a marked surface (for different materials : metals and dielectrics) as a third data storage axis. The idea is to convert a performed depth in a grey level in the reading procedure. This marking depth can be then used for coding. Best results are obtained with polymers when transmission lightening is used for reading.
Ultrafast laser micromachining results depend on both the processing parameters and the material ... more Ultrafast laser micromachining results depend on both the processing parameters and the material properties. The thermal effects are negligible if a good combination of processing parameters is chosen. However, optimizing the processing parameters to achieve the required surface quality on a given material can be quite complex and time consuming. Within the framework of the European LAMpAS project, we developed a model to estimate the heat accumulation on a surface as a function of the laser fluence, scanning speed and line pitch. The simulation results were correlated with experimental ones. The predictions of the model allow evaluation of the heat distribution on the surface, and optimize the ultrafast laser micromachining strategy, yielding negligible thermal damage.
Ablation by ultrafast lasers results from a series of complex nonlinear phenomena of absorption a... more Ablation by ultrafast lasers results from a series of complex nonlinear phenomena of absorption and transfer of energy that take place in the surfaces of materials upon irradiation. Provided that a good window of processing parameters is chosen, the resulting thermal effects are in general negligible, making ultrafast lasers excellent micromachining tools applicable to most types of materials. It is thus beneficial to understand how ablation is affected by the laser processing parameters and the material properties, in order to optimize the micromachining processes. We propose an engineering model to estimate the dimensions of ablation, taking into account on the one hand the material properties such as the ablation threshold, penetration depth and the refractive index and, on the other hand, the processing parameters namely the pulse energy and beam diameter, scanning speed, repetition rate and angle of incidence. The model considers as well the effects of incubation, changes of topography during multi-pulse irradiation, surface reflectivity and Gaussian beam diameter variation with the distance to the focal plane. The model is able to simulate the profiles of ablation surfaces produced by normal or tilted laser beam, either for spot, line and area processing. The results obtained are validated by comparison to the ones obtained experimentally. Both the model and the experiments focus on stainless steel. The predictions of the model also allow for the optimization of the micromachining process, both energy and time wise.
Le développement actuel de la technologie induit une constante nécessité d’obtenir des tailles de... more Le développement actuel de la technologie induit une constante nécessité d’obtenir des tailles de plus en plus petites pouvant descendre jusqu’à des dimensions micrométriques et sub -micrométriques. L’ablation laser, qui a le grand avantage d’un enlèvement de matière très précis, est un candidat prometteur. Dans cette thèse on démontre la faisabilité de tirer avantage des impulsions laser femtosecondes avec la matière pour la micro et nano structuration, et ceci en ayant développé une machine compacte de grande précision et flexibilité. Une approche théorique comparant les régimes d’interaction à haute et basse cadence est présentée. Des investigations de l’efficacité du temps de procédé aussi bien que l’effet de la cadence pendant l’ablation de métaux ont été effectuées. Le potentiel de l’outil multifonctionnel couplé avec un oscillateur laser femtoseconde à haute cadence est montré pour différentes applications en biotechnologie. Les résultats sur la cartographie d’une large zone ...
Interview with David Bruneel, laser engineer and working at the R&D department of LASEA. This Bel... more Interview with David Bruneel, laser engineer and working at the R&D department of LASEA. This Belgian company which specialises in the production of laser micromachining systems, is a partner of the H2020 project Laser4Surf. David Bruneel talked with the European Science Communication Institute (ESCI) about shaping metal surfaces with nanosized structures and the market potential for such surfaces.
The benefits of replacing space and energy consuming actuators and sensors with so-called “active... more The benefits of replacing space and energy consuming actuators and sensors with so-called “active” materials have been well known for decades. One such material, shape memory alloys (SMAs), inspire particularly novel applications because of their unmatched power density, high force output, and ability to be multifunctional – acting simultaneously as both actuator and sensor. Recently, improved material processing techniques by companies such as Dynalloy have enabled repeatable, low-cost production of small-diameter (<100 µm) SMA wires capable of being actuated with minimal power at rates faster than 1 Hz. Additionally, a multifunctional power controller has been developed at North Carolina State University to simultaneously control the heating power input to SMA wires while measuring their changing electrical resistance. Advances such as these have enabled new applications to be considered in academia, such as steerable catheters and guidewires for use inside the human body, ligh...
Enabling of continuous photomasking using a pulsed laser source and polygon scanners to achieve h... more Enabling of continuous photomasking using a pulsed laser source and polygon scanners to achieve high repetition rates and pulse energy, precise beam guiding and stable handling of the moving web with the applied photomask resist.
The advantages of the femtosecond laser for micromachining of materials have been widely demonstr... more The advantages of the femtosecond laser for micromachining of materials have been widely demonstrated allowing the laser micromachining to reach a level of accuracy in the micrometer range level. However, most of the current femtosecond laser micromachining applications are for flat surfaces, 2D or 2.5D, requiring different kinds of machining: drilling, cutting, and texturing, for more and more exotic materials. Biomedical implants are a part of those new objects requiring very high level of accuracy and surface finish, and for complex geometries: cylindrical or hemispherical shapes. LASEA has developed a system combining femtosecond laser with 7 simultaneously moving axes: 5 mechanical axes and 2 galvanometric axes. This combines the 3D micromachining offered by the 5 axes with the fast scanning. The laser parameters and strategies are controlled owing to laser specific developed functionalities. Another challenge to overcome is the research of laser parameters which is time and ma...
It has been thoroughly demonstrated in the past years that ultrafast lasers are excellent tools f... more It has been thoroughly demonstrated in the past years that ultrafast lasers are excellent tools for micromachining virtually all types of materials, provided that a good window of processing parameters is chosen so that the resulting thermal effects are negligible.The ablation topography resulting by irradiation with these lasers typically depend on several factors related both to the laser beam and the material characteristics. As a consequence, the search for the optimal processing parameters that lead to some required ablation dimensions on a given material can be time consuming.To enhance this parameters search, LASEA developed the application tool LS-Plume®, based on a numerical model that allows estimating the ablation profiles of scanned lines and areas, as well as drilled cavities. The processing parameters required to run the application are the pulse energy, beam waist at the focus, pulse repetition rate, scanning speed and beam tilting angle, whereas the characteristics o...
Le developpement actuel de la technologie induit une constante necessite d’obtenir des tailles de... more Le developpement actuel de la technologie induit une constante necessite d’obtenir des tailles de plus en plus petites pouvant descendre jusqu’a des dimensions micrometriques et sub -micrometriques. L’ablation laser, qui a le grand avantage d’un enlevement de matiere tres precis, est un candidat prometteur. Dans cette these on demontre la faisabilite de tirer avantage des impulsions laser femtosecondes avec la matiere pour la micro et nano structuration, et ceci en ayant developpe une machine compacte de grande precision et flexibilite. Une approche theorique comparant les regimes d’interaction a haute et basse cadence est presentee. Des investigations de l’efficacite du temps de procede aussi bien que l’effet de la cadence pendant l’ablation de metaux ont ete effectuees. Le potentiel de l’outil multifonctionnel couple avec un oscillateur laser femtoseconde a haute cadence est montre pour differentes applications en biotechnologie. Les resultats sur la cartographie d’une large zone ...
We report on high-quality high-throughput laser milling of silicon with a sub-ps laser delivering... more We report on high-quality high-throughput laser milling of silicon with a sub-ps laser delivering more than 1 kW of average laser power on the workpiece. In order to avoid heat accumulation effects, the processing strategy for high-quality laser milling was adapted to the available average power by using five-pulse bursts, a large beam diameter of 372 µm to limit the peak fluence per pulse to approximately 0.7 J / c m 2 , and a high feed rate of 24 m/s. As a result, smooth surfaces with a low roughness of S a ≤ 0.6 µ m were achieved up to the investigated milling depth of 313 µm while maintaining a high material removal rate of 230 m m 3 / min .
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