High average power femtosecond (from 100 W to 1 kW) with higher productivity open access to new and large markets of “macro” processing (Aeronautics, Energy and Mobility) unreachable so far for femtosecond laser processing, more devoted to micro processing (microelectronics). The main challenge is to find the right way to exploit the laser power, the solutions being somewhat different for each case. This work presents an example of optimization in the technical field of aerodynamic performances.

We report on a high-performance laser milling process and system for the fabrication of large arbitrarily shaped geometrical structures in silicon. A custom designed multi-step approach, combining high speed nanosecond laser ablation (roughing) with high precision ultrashort pulsed ablation (finishing) and inline 3D-measurement allows for the realization of large-volume cavities of up to and exceeding 20 mm³ with virtually freely selectable geometry at very high ablation rates R_abl > 0.1 mm³/s while maintaining high surface quality (S_a < 0.5 μm) on the laser processed areas. During the roughing step, nanosecond laser ablation creates the coarse structure of the target geometry. Subsequently, a white-light interferometer obtains a 3D image of the raw shape, enabling a purpose developed algorithm to compute an individual finishing laser pattern by comparing actual and target geometry. The following ultrashort-pulsed laser finishing step creates the final geometry by precisely removing surplus material according to the computed pattern. Depending on the absolute ablation volume and the precision requirements, several finishing steps are conducted successively to generate smooth functional surfaces. The achievable structure quality crucially depends on the perfect alignment of the measured 3D data and the applied laser ablation pattern. Thus, a high precision machine platform connects laser process and measurement modules by an automated handling system. Camera based alignment systems provide long-time repeatable positioning accuracies < 5 μm, which allow for reliable high-volume wafer processing.

In this contribution we show through via drillings in dielectrics by ultrafast laser top-down percussion drilling in GHzburst mode. We point out some limitations that occur during the drilling process and show how to overcome these. Finally, we obtained through vias of almost constant diameter in Sodalime glass, which might be of interest in the microelectronics industry for the fabrication of glass interposers.

We compare different pulse durations, modes and repetition rates of infrared ultrashort pulses lasers for the inscription of printed electronics sensors under 100 μm scale. We investigate pulse widths varying from 200 fs up to 10 ps, and standard single pulse versus 5 GHz burst regimes to produce the most efficient and cleanest ablation. The aim of the investigated process is to ablate a layer of conductive material like carbon, NiAl or NiCr forming the electronic track contours, without damaging the support which is made of a dielectric insulator. Depending on the materials and substrates of the printed electronics circuits, we have observed that 10 ps pulses in GHz burst regime with moderate individual pulse energy (around 10 μJ) have a lot of potential for an efficient production.

Adaptable intensity distributions and parallelization of laser beams are of interest to enhance the processing efficiency for more and more laser applications. The parallelization of laser beams based on beam splitting diffractive optical elements (DOE) and a 2D galvanometer scanner is state of the art. The use of a beam splitting DOE in combination with a 2D galvanometer scanner introduces problems that need to be overcome to achieve a satisfactory result: a scanner-induced distortion of the DOE-generated spot matrix occurs in the working plane and the spot matrix twists as a function of the deflection angle of the scanner mirrors. Common setups employ either static relay lenses for multi-beam systems or additional actuators to increase spot position accuracy. We combine these two approaches in a cascaded optical system using a dynamically rotatable DOE. The achievable accuracy is evaluated with a simulation tool developed specifically for a typical optical configuration for multi-beam laser materials processing. In addition, a first functional prototype with a rotating DOE is demonstrated. The cascaded rotating DOE offers potential for flexible parallel laser processes.

Significant performance improvement of modern laser technologies such as welding, additive manufacturing, brazing, cladding, sheet metal cutting, based on the use of multi-kW multimode fiber lasers, fiber-coupled solid-state and diode lasers, can be improved using beam shaping optics providing optimal energy distribution by splitting the laser beam into several beamlets creating by further focusing separate multiple spots in the working plane and variable sharing energy between these spots. Various multi-spot patterns, such as square, line, rhombus, consisting of 4 or 9 separate spots, allow eliminating or reducing spatter, realizing optimum temperature distribution in the melt pool and stabilizing the processes in welding of tailored blanks, copper and aluminium parts in the production of batteries, zinc coated steel, cladding. Multimode lasers are characterized by low spatial coherence (large BPP or M² values), therefore the most reliable optical approach to control the intensity distribution is imaging the fiber end with a collimator and a focusing objective. The proposed multi-spot beam shaping method presents a combination of fiber end imaging and geometrical separation of focused spots perpendicular to the optical axis, thus creating a compound working spot, called as quattroXX-spot or peaXXus-spot, as a combination of several spots. Varying the energy portions in separate spots and the distances between them make it possible to optimize for a particular application common intensity distribution of the compound spot. To ensure reliable operation with multi-kW lasers and to avoid optics damage the multi-focus optical devices are designed as refractive elements with smooth optical surfaces made of optical materials self-compensating thermo-optical effects that provides insignificant thermal lensing and, hence, negligible thermal focus shift and spherical aberration. The paper presents the proposed multi-spot optics, shows intensity profile measurements and application results.

We investigate the focusing performance of optical tools for materials processing with ultrashort laser pulses. Here, focus distributions generated by high-NA microscope objectives and f-theta objectives are evaluated in terms of peak intensities and symmetry breaks when pulses of ≲ 100 fs are applied. With our simulations, we additionally examine the effects of spatial beam shaping and uncover associated spatio-temporal focusing phenomena, when diffractive optical concepts are used, for example, to shape customized non-diffracting beams or 3D-focus distributions.

Holographic beam shaping that is performed with a computer-generated hologram displayed on a spatial light modulator is very useful for many kinds of scientific and engineered applications. The temporal and spatial stabilization is indispensable for them, especially, for the material laser processing, because it requires a high-quality beam in short and long terms. In our research, the stabilization is performed with an observation of the intensity distribution that is easily detected by simple optics and an ordinary imager. The reconstruction of the computer-generated hologram is iteratively optimized according to the holographic reconstruction on the Fourier space. The performance of the beam shaping is estimated under the application of laser processing of glass.

A promising approach for enhancing the electrochemical properties of a lithium-ion battery is the combination of a highvoltage cathode with a three-dimensional (3D) electrode architecture created through ultrafast laser ablation. In this work, the ablation characteristics of LiNi_0.5Mn_1.5O₄ (LNMO) cathodes either fabricated by an N-methyl-2-pyrrolidone-based (NMP) or water-based electrode processing were examined. The influence of the binder on the resulting ablation depth as well as the ablation area and volume of the generated grooves was analyzed. An electrochemical analysis of unstructured and selected laser structured LNMO cathodes of both binder types was conducted to characterize the influence of the 3D electrode design on the electrochemical performance. For both LNMO cathodes, a significant increase of the specific discharge capacity at a C-rate of 5C could be observed for the cells containing the laser structured electrode variants.

Extensive technological progress is essential to meet the ambitious future requirements of energy storage devices. This is due to the necessity of achieving high energy and power density operations, accompanied by high safety standards and extended lifespans, while maintaining low production and material costs. Significant importance is placed on the research of high energy active materials. However, besides material optimization, there is substantial potential for optimization by introducing electrodes with high mass loading, advanced electrode architectures, and their transfer to production level. Achieving appropriate trade-offs between high energy and power density, process reliability, and economic considerations poses a challenge for current lithium-ion battery technology. For this purpose, the laser-assisted generation of three-dimensional (3D) electrode architectures is studied and evaluated. Advanced electrode design incorporates micro and sub-micron structures that can be designed in various ways. Significant improvements in battery lifespan and high-power operation capabilities can be achieved compared to traditional two-dimensional (2D) electrodes. Furthermore, the production of 3D electrodes with laser processing requires coordination with other established manufacturing steps in the battery production process. In particular, the calendering of electrodes holds great importance as it has a significant impact on the microstructural properties of the composite electrode, including porosity, material density, and film adhesion strength. This study investigated the impact of laser-induced hierarchical structuring, comprising micro-/nano-porosities and microtopography, on electrodes with varying mass loadings from 2 mAh/cm² to 6 mAh/cm². In this regard, cells comprising graphite anodes and lithium-nickel-manganese-cobalt oxide cathodes were prepared and subjected to electrochemical characterization techniques.

To develop a safe and sustainable infrastructure for future missions, In-Space Manufacturing must become state of the art. This paper will propose a novel handling mechanism for powder-based material suitable for the microgravitational environment. Ultrasonic levitation is a promising technology for gravity-independent material handling. The fundamental challenge lies in the trapping of powder-based materials. To assist the material deposition process and stabilize the material handling water is used as a carrier material. A multi-emitter single-axis ultrasonic levitator is employed to levitate PA 12 SLS-powder in a fixed state and initiate a laser melting process to bind the powder material. The spherical levitator uses 72 piezoelectric transducers by Murata, with a levitation radius of 37 mm, which can generate a levitation force of up to 0.15 mN. A 20 W 1064 nm fiber laser is employed to evaporate the water and bind 0.4 μg PA 12 particles together. The experiments will be performed under earth and atmospheric conditions. This paper investigates the evaporation time of water inside a levitation field depending on the laser power. The properties and parameters of distinguished materials will be evaluated to determine the boundary conditions of the acoustic levitator. The data will be compared to a simplified analytical model and used to initiate a melting process with the SLS material.

Real-time monitoring of the laser surface texturing is very important to maintain the process in control and identify any geometrical deviations of the surface features from their referenced/predefined values. In this research, a novel compact in-line/in-axis monitoring system is reported. The system employs light diffractometry principle to extract geometrical information about the laser generated surface topographies and thus to judge if the process is in control. A collimated white light is focused through the laser beam delivery sub-system that integrates beam deflectors and a telecentric lens onto the workpiece. Then, the reflected light from the textured surface is sent back through the same optical path to a spectrometer. As the collimated white light is diffracted by the periodic surface structures, only the 0-order diffracted light is reflected to the spectrometer. The reflected spectra are dependent on the periodicity, depth, and amplitude of the surface features as they diffract the focused white light beam. Thus, by capturing the spectra from fields processed under different conditions, especially one with zero focal offset distance (FoD) and others with a varying FoDs, it can be determined if such processing disturbance is present. Then, the collected data is used to train machine learning (ML) classifiers, which can automatically detect the presence of any focal offset during the laser texturing operations. In this regard, decision tree (DT) ML classifier is trained. The obtained results show that significant dimensionality reduction and high levels of classification accuracy can be achieved using DT, with up to 99% accuracy based on the full reflection spectrum and 93% with reduced spectra. Based on its in-built dimensional reduction capabilities, inherent interpretability, and reduced prediction latencies, DT approach offers unique advantages and can be considered for further inline/in-axis monitoring tasks depending on the specific surface features that should be monitored.

We report on the recording of the near and far field intensity beam profiles to train a convolutional neural network, which is aimed to online detect system aberrations of an ultrafast laser amplifier. We extend the state of the art by implementing a spiral phase plate to use the concept of phase diversity. It is found that the underlying optical field in amplitude and phase can be accurately revealed.

Laser welding is a manufacturing process widely used in the industry to efficiently join parts together, generally through a characteristic deep penetration melt pool. Its benefits, like no-contact welding, no tool wear and fast processing, are very relevant for many industrial applications. Nonetheless, finding the optimal parameters for each specific processes remains challenging and time-consuming. Involving many physical phenomena, such as laser-matter interaction, thermodynamics and fluid mechanics, the process parameters have many nonlinear interactions. In these circumstances, a cost and time-effective Design of Experiment (DoE) is nearly impossible to generate. Furthermore, thorough weld characterisation, from geometrical to metallurgical analysis, remains a labor-intensive and expensive task. In this study, we compared different regressors powered by Artificial Intelligence such as Gradient Boosted Decision Trees, Gaussian Process Regressors, Perceptrons trained on readily available data from previous trials done at IREPA LASER, to predict the depth of penetration of the weld. To develop the model with industrial use in mind, the material, the processing parameters and the optical setup were used as the input parameters. A R² of 0.94 and a Mean Squared Error of 0.25mm² are obtained from the model developed. Scores are then compared to the state of the art, taking into consideration the size and number of parameters of the dataset used.

Surface-enhanced Raman spectroscopy (SERS) is a well-known label-free analytical technique for chemical and biological detection. Electromagnetic enhancement near the nanostructured surfaces contribute to the SERS performance. However, the substrate-based nanostructured SERS surfaces are conventionally fabricated by time- and resource-intensive techniques. Herewith, a cost-effective and scalable process chain to fabricate disposable thermoplastic SERS substrates is investigated. The surface design includes a multiscale topography that consist of single-tier laser-induced periodic surface structures (LIPSS) encircled by two-tier hierarchical structures (HS). Different types of LIPSS were investigated, generated by linear and circular polarisation of the laser. The process chain employed to produce high performance SERS substrates include, first, ultrashort laser-enabled fabrication of a textured metallic masters and then replication of functional topographies on Cyclic Olefin Copolymer (COC) using hot embossing and finally mask-coating the LIPSS ‘hot spot’ with gold for an electromagnetic enhancement. The HS topographies facilitated the superhydrophobic evaporation of samples to enrich the analytes onto the SERS ‘hot spot’ on the COC substrates. An electromagnetic enhancement factor of 107 was achieved on the SERS substrates employing the proposed process chain. The SERS enhancement of such multi-scale functional topography was analysed and a detection limit of up to 10-7 M of methylene blue and 4-MBA was achieved. The proposed cost-effective process chain can pave the way for the broader use of SERS for detecting analytes in food and agricultural sectors.

Ice accretion on external aircraft surfaces due to the impact of supercooled water droplets can negatively affect the aerodynamic performance and increases fuel consumption and reduces operational capability. To prevent it, different approaches to develop anti-icing and de-icing surfaces able to delay ice nucleation and to easily remove it respectively, have been explored in the recent years. All these approaches can be classified into two major categories: active and passive approaches. In the latter case, creating an anti-icing surface is mainly achieved by changing surface morphology and chemistry to regulate the interaction between water/ice and the cold surface. Superhydrophobicity is postulated as a key surface property to prevent the condensation of water droplets on the surface and thus, delaying ice formation. In this research, novel research progress on the correlation between superhydrophobic properties of hierarchical patterns on aluminum created by ultrashort laser pulses and the reduction of ice-adhesion is reported. Three different Hierarchical Structures (HSs) were fabricated by direct laser texturing with femtosecond pulses. Wettability performance of HSs was evaluated over the time to assess their wettability transition from hydrophilic to superhydrophobic. Based on that, specific storage conditions on organic atmosphere were defined to guarantee reliable superhydrophobic performance several hours after manufacturing. The functional behavior of three HSs generated on 40×80 aluminum plates were assessed by a climate chamber able to simulate freezing weather. Differences in terms of amount of ice growth and mechanism of ice nucleation were found for the studied HSs surfaces. Additionally, several icing and de-icing cycles were performed to evaluate the wear of HSs on wettability properties and anti-icing behavior of the aluminum substrates.

2D molybdenum disulfide (MoS2) is a promising material for the application in the flexible electronic, where large, uniform, crystalline films on flexible substrates are desired. The utilization of low-temperature plasma-enhanced atomic layer deposition (PEALD) facilitates the production of large-area, uniform, polycrystalline MoS2 films on temperature-sensitive substrates. However, for next-generation electronics, the crystallite size does not fulfill requirements. In order to enhance the degree of crystallinity conventional high temperature post treatments of the whole sample, which are not compatible with flexible substrates, needs to be avoided. In this study, a method for increasing the crystallinity of polycrystalline MoS2 films on SiO₂/Si and glass substrate deposited by plasma enhanced ALD processed with femtosecond laser pulses (λ = 1030 nm, t_p = 200 fs), in a "cold" annealing process is presented. The laser fluence range varies from f_min = 3.0 mJ cm⁻² to f_max = 30.00 m J⁻² with scanning speeds from v_scan,min = 1 mm s⁻¹ to v_scan,max = 1000 mm s⁻¹, at a repetition rate of f^rep = 2000 kHz. The crystallization and the influence of the processing parameters on the film topography are analyzed in detail by Raman spectroscopy and scanning electron microscopy. Finally, the influence of the laser processing on the film resistivity is investigated.

In this study, we utilize Laser-Induced Forward Transfer (LIFT) technology to digitally integrate single-layer graphene pixels, as well as source and drain (S/D) metal electrodes, onto PDMS and Kapton PI substrates. This is done for the purpose of developing a flexible Graphene Field Effect Transistor (GFET). We showcase the direct integration of intact graphene pixels with lateral dimensions ranging from 40 to 200 μm in between the S/D electrodes. The transferred pixels exhibit high structural quality and a low defect density due to the solvent-free, single-step transfer process. To attain this level of transfer quality, we conducted a thorough investigation and optimization of the laser transfer process parameters (e.g. laser fluence, beam shape and size, alignment), tailored to the flexible substrates we're interested in. The structural integrity of the transferred pixels was confirmed through characterization techniques involving optical microscopy, Raman spectroscopy, and electrical measurements. Furthermore, we fabricated the Source, Drain, and Gate electrodes using a combination of LIFT and laser sintering of metal nanoparticle inks. Initially, we achieved the fabrication of micro-patterns with the desired geometry and a minimum feature size of < 50 μm, through LIFT. Subsequently, laser sintering, a method fully compatible with metal nanoparticle inks or pastes and thermally sensitive substrates, was selectively applied to the printed patterns, resulting in high electrical conductivity (with reported resistivity as low as 3 times the bulk value). The electrical performance of the laser-printed and sintered patterns was assessed using a 4-point probe IV station. The results we demonstrated underscore the adaptability and versatility of LIFT for transferring low-dimensional materials, particularly single-layer graphene and metal nanoparticles with an average diameter of 50 nm. This technology provides a digital solution for addressing complex use-cases and applications in the field of electronics, particularly for the next generation of flexible GFETs.

We present the fabrication of high-quality graphitic micro-wires in diamond which are conductive in nature using pulsed Bessel beams. The electrodes are created in the bulk of 500 μm thick monocrystalline CVD and HPHT diamond samples perpendicular to the sample surface without sample translation or beam scanning. The role of various beam parameters such as pulse energy and pulse duration, different crystallographic orientations of the sample and two different writing modes of the laser namely burst mode and single-pulse mode in the conductivity of such electrodes are investigated. While the morphology of the electrodes is analysed using optical microscopy, the conductivity is measured experimentally using current-voltage characterisation. Furthermore, micro-Raman spectroscopy is implemented to investigate the graphitic content of electrodes fabricated. We have observed that higher pulse duration favours better conductivity while pulse energy has an optimum value for the same. As for the crystallographic orientations, we have found that it is possible to eradicate the potential barrier in the current-voltage curves completely even for graphitic wires fabricated at low pulse energy and in the fs pulse duration regime in a (110) oriented sample in contrast to the (100) oriented-crystal case where the barrier is generally observed. Finally, in case of wires fabricated with laser bursts with femtosecond sub-pulses, the higher number of sub-pulses, lower time delay between them and longer total burst duration favours better conductivity. Through various optimisation techniques, we report resistivity values as low as 0.01 Ω cm for the Bessel beam written electrodes in diamond.

We demonstrate how the implementation of an axicon-lens doublet can lead to an efficient beam-shaping solution for laser processing of semiconductors. By generating high-angle pseudo-Bessel beams with 50-ps 1550-nm pulses, we can write high-aspect-ratio structures inside silicon and approach results similar to those today demonstrated in dielectrics. For the first time, we show how repeated laser irradiations with our shaped beam lead to permanent modifications that spontaneously grow shot-after-shot from the front to the rear surface of 1-mm thick crystalline wafers. Although direct microexplosion and drilling remain inaccessible, our work evidences a novel self-induced percussion writing modality leading to the formation of uniform and reproducible elongated modifications with aspect ratios as high as ∼700, obtained without any relative motion of the beam focus. Quantitative phaseimaging reveals light-guiding characteristics associated to these structures, according to a measured high positive index change exceeding ∼10⁻². This opens the door to unique monolithic solutions for optical through-siliconvias, which could be potentially a key element for ultrafast vertical interconnections in next-generation silicon chips.

Femtosecond laser-based 3D printing has strongly improved the field of photonics, enabling the fabrication of complex optical components. In this study, we present the development and characterization of a bulk Bragg grating sensor created using the FEMTOprint system, which integrates a femtosecond laser for high-precision structuring. The latter enables the direct writing of waveguides with Bragg gratings within a transparent substrate. This unique manufacturing process grants control over the waveguide's geometry, grating period, and refractive index modulation, resulting in sensor capable of extraordinary sensitivity. We conducted a characterization of the waveguide with a Bragg grating sensor to assess its performance. Our results demonstrate remarkable sensitivity to environmental parameters, with a temperature sensitivity of 10.51 pm/°C and a mechanical strain sensitivity of 1.22 pm/με. These characteristics make the sensor ideal for a wide range of applications, including temperature monitoring and structural health assessment. The innovative combination of femtosecond laser printing and Bragg grating technology offers a new dimension to the design and application of optical sensors. Our research not only highlights the unique capabilities of these sensors but also opens up exciting prospects for future developments and interdisciplinary collaborations.

Fiber Bragg gratings are widely used for optical sensing applications, including their deployment in harsh environments. The use of Type III femtosecond gratings shows a prominent interest due to their ability to withstand very high temperatures (over 1000°C for 100’s of hours). These Type III fiber Bragg gratings correspond to a periodic structure of micro-voids generated by femtosecond-laser in silica-based optical fibers, fabricated by the point-by-point technique. The physicochemical characteristics of the micro-voids were investigated by quantitative phase microscopy technique and their thermal stability monitored through isochronal annealing experiments up to 1250°C.

The automotive industry has made significant advancements regarding the safety technology. Thus, airbags play a pivotal role in protecting passengers during accidents, therefore saving more lives and preventing serious injuries. The precise cutting of airbag textile materials is one of the important processes for ensuring the effectiveness and performance of such equipment. The aim of this work is to compare three scanning systems employed for CO2 laser cutting of airbag textile material in the automotive sector: (i) a plotter system (i.e., a traditional laser cutting setup with a fixed cutting bed); (ii) fixed 2D galvanometer scanner (GS), commonly used for laser cutting in more compact and automated environments; (iii) mobile 2D GS, with an increased portability and versatility in comparison to the previous solution. These three systems have been installed and utilized in an industrial facility for airbags manufacturing. The specific parameters, advantages and drawbacks of each system for the targeted application have been compared. Examples of applications are presented – from the industrial site where we have implemented and utilized them. The choice between different such scanning systems for laser manufacturing are discussed in the trade-off between quality and productivity.

Laser powder bed fusion (LPBF) can rapidly manufacture the metal products with complex structures, but the high surface roughness and low dimensional accuracy limit the mechanical properties and application scenarios of powder bed process parts. Because in recent years, the ultrafast laser micromachining has shown great potential in the field of precision machining, it was combined with laser powder bed manufacturing. It means that after additive manufacturing samples, those were micromachined using ultrafast laser. In current study, a laser powder bed fusion device, equipped with a picosecond laser, is described, and a preliminary realization of additive and subtractive manufacturing based on pulsed laser processing using this device is presented. The side surface roughness of the samples fabricated by hybrid additive manufacturing process was lower than that of samples built LPBF technology. This study may provide a new way to manufacture parts with high dimension accuracy and low surface roughness by LPBF technology.

The behavior of three commonly used commercial polymers (poly(vinyl chloride) (PVC), poly(ethylene terephthalate) (PET) and polypropylene (PP)) under high repetition rate (10 kHz – 1 MHz) femtosecond (450 fs) laser irradiation at λ=515 nm (1.40 J/cm²) is analysed. A study of how repetition rate affects the heat accumulation effects and the processing outcomes on the surface of these polymers is presented, demonstrating a tailored modulation of ablation depth and modified widths through repetition rate variations at constant values of fluence and number of pulses. Micro Raman analyses are conducted to investigate the induced thermal degradation in the surroundings of the ablated regions for processing at different values of repetition rates.

The microstructure of nuclear fuel undergoes significant changes under irradiation, necessitating access to specific areas within fuel pellets for post-irradiation examinations, particularly for studying the release of fission gases resulting from post-accidental reactions in events such as Reactivity Initiated Accidents (RIA) and/or Loss of Coolant Accidents (LOCA), or for studying material properties. The objective of developing a micro-machining approach preserving the physicochemical integrity of the worked piece while minimizing thermal and mechanical effects is essential. We propose a high-resolution and non-destructive method, ultrafast laser ablation micro-machining, as an innovative solution for this application. We present experimental and numerical studies aimed at evaluating the feasibility of applying this process to the preparation of irradiated UO₂ samples of various dimensions (ranging from μm to cm). Our preliminary work on graphite, as a model material, validates the feasibility of this approach, and we intend to transfer the technique to non-irradiated UO₂ and eventually apply it to irradiated material.

A simple method for the simultaneous inscription of two spectrally separated fiber Bragg gratings (FBGs) with a femtosecond laser at the same spatial spot is presented. The inscription setup consists of the following elements, i.e., an amplified near-IR femtosecond laser, two identical Phase-Masks (PM), two cylindrical focusing lenses, a negative defocusing spherical lens and a 50%:50% beam splitter. The inscription beam is divided into two equal beams each containing ~50% of the energy by means of a beam splitter. Each beam is then focused on the same spatial spot of the optical fiber through a 2140 nm period PM and a cylindrical lens. One beam is focused from one side, while the other beam is focused on the same spot, but from the opposite side. This ensures the simultaneous inscription of two FBGs at the same spatial spot. The wavelength separation is achieved by defocusing one of the beams with a negative spherical lens. The transmission and reflection spectrum of the two FBGs are measured. The center Bragg wavelength of the shorter FBG is ~1548.6 nm, and the center Bragg wavelength of the longer FBG is ~1553.9 nm or ~1550.4 nm when using a defocusing lens of −400 mm or −1000 mm, respectively, in the second inscription beam path. The measured transmission dip of all FBGs is greater than −4 dB.

The use of femtosecond laser nanostructuring to generate Laser-Induced Periodic Surface Structures (LIPSS) is a well-known and robust technology customized for a wide variety of materials. As a low-cost and high-throughput technique it can be applied in fast and large-scale manufacturing. Nevertheless, the quality of LIPSS strongly depends on the optical properties of the light beam (such as its uniformity and polarization state) and the homogeneity of the surface. Therefore, manufactured LIPSS are frequently far from ideal. A key feature of LIPSS is their ability to modulate the polarization state of transmitted or reflected radiation. In this work, we analyze how random fluctuations of LIPSS topography, and randomness of the LIPSS parameters, modify the polarimetric properties of the output beam. We have focused on LIPSS manufactured over steel surfaces. For this, we have computed the electromagnetic field reflected by the surface using a Finite Element Method for different incident polarizations. Finally, the Stokes parameters of the reflected light has been numerically computed, and compared with the ones characterizing the beam after reflection on an ideal periodic LIPSS topography.

Diffractive Optical Elements (DOEs) are micro-structed devices which modulate the amplitude, phase, or polarization of a light beam. In this work, we use femtosecond laser direct writing (FLDW) and lithography techniques to manufacture binary phase DOEs which produce high quality intensity distributions for different fs-laser micromachining. We have designed DOEs whose intensity pattern contains an intense square flap-top to produce ablation with two less intense areas, one before for heating and one after for polishing the material. Then, we manufactured these phase DOEs over a dielectric material, fused silica. The phase modulation is produced by the optical path difference due to the topography induced by ablation. Finally, we have analyzed the structure of these DOEs, i.e. their phase shift and roughness, reaching an average roughness of 49.15 nm and a phase shift of 1.014π, very close to the designed value, π. Moreover, we study the far-field diffraction patterns of the engraved DOEs, which are in good agreement with the theoretical ones.

Laser percussion drilling of micro-holes has established itself as a prominent micro-machining technique rivalling both conventional and non-conventional micro-drilling processes. Despite its broader use, the laser percussion drilling process has some limitations, particularly the achievable micro-holes’ accuracy. The research reports a novel method to address this shortcoming by improving the holes’ dimensional and geometrical accuracy. Especially, the proposed two-side method for laser percussion drilling of micro holes utilizes a penetrating laser beam that is refocused at the hole exit by employing a reflective concave mirror lens. In this way, an additional ablation occurs at the hole exit to improve the hole accuracy. Especially, the exit size of the holes increases and simultaneously their cylindricity is improved while the tapering angle is reduced. Notably, these improvements are achieved without affecting the processing efficiency whereas the proposed laser drilling setup is relatively simple to implement.

Laser nanotechnologies have enormous potential for bringing products with new surface functionalities to market, while meeting sustainable development objectives. However, SMEs and start-ups are not benefiting fully from these technologies because of their cost and the necessary access to testing and validation infrastructures. The Horizon 2020-funded NewSkin project has thus created an Open Innovation Test Bed (OITB) focused on surface nanotechnologies to overcome these challenges. It provides access to scale-up and testing facilities to enhance surface properties in different relevant sectors. Regarding laser nanotechnologies, NewSkin provides access to different laser up-scaling facilities that integrate innovative manufacturing processes, including surface texturing, roll-to-roll femtosecond laser texturing, heat-treatment laser, multimodal laser processing. Several companies and research organisations have benefited from these technologies to improve surface functionalities such as wettability properties, improved heat exchange, friction reduction, wear resistance. The creation of NewSkin AISBL will further accelerate the uptake of innovative laser processes to manufacture new nanoenabled products.

Patterning liquid metal is a promising electrode material for soft electronics. In order to obtain controllable and fine liquid metal patterning, in this study, a superhydrophobic PDMS surface was fabricated using a femtosecond laser to adhere to liquid metal circuits selectively. A trapezoidal hierarchical micro/nanostructure was fabricated as the surface of PDMS was ablated by laser irradiation at a distance of 30 μm. As a result, the roughness of the surface increases, and the liquid metal adheres easily to the non-laser-treated area, but the liquid metal does not adhere to the laser-treated area. This method made various high-resolution liquid metal patterns with a line width of at least 40 μm. This method is fast, simple, inexpensive, does not require additional vacuum equipment, and is expected to be highly applicable, such as fabricating wearable devices, soft electronics.

This study introduces a groundbreaking approach to micro/nanoscale patterning by synergistically combining Two- Photon Polymerization (TPP) with Digital Micro Mirror Device (DMD) technology. By leveraging a femtosecond laser and employing a novel grayscale lithography method via the DMD, we have significantly optimized both the throughput and resolution of patterning processes beyond the traditional diffraction limit. Our methodology enables the precise fabrication of complex 3D nano-structures as well as intricate 2D patterns, addressing long-standing throughput and resolution challenges in TPP. Through simulations of the Point Spread Function (PSF) and meticulous adjustments to the DMD's grayscale modulation, we achieved uniform light intensity and high-resolution patterning, demonstrating the potential of this approach to revolutionize micro and nanoscale fabrication. The successful integration of DMD-enhanced femtosecond laser patterning with TPP opens new avenues for the development of advanced devices across various fields, from biomedical engineering to microelectronics, setting a new benchmark for precision and efficiency in digital patterning technologies.

We present simulation and experimental results of the ablation and dicing process of a silicon wafer using a passive Q-switch nanosecond (ns) Tm: YAP lab laser operating at a wavelength of 1.940μm. This study aims to show that in the 2μm range lasers, high precision in the silicon ablation process can be achieved and can compete with existing industrial lasers in the ultraviolet or near-infrared range. At low fluences, silicon appears to be transparent when irradiated by 2μm lasers. Above a fluence threshold of 3.8J/cm², third-order nonlinear effects, such as the lens converging Kerr n₂ and the two-photon absorption β_TPA effects, turn the silicon into an absorbing medium, improving the ablation process. At room temperature of 300°K, n₂ = 12×10⁻⁵±2.0×10⁻⁵cm²/GW and β_TPA = 0.56±0.02cm/GW, the resulting nonlinear factor of merit NFOM = 2.1 ± 2.0 is very large; conferring a self-focusing lensing action on the silicon. Based on a Comsol simulation, we observe that the silicon/Q-switch laser interaction shows that the Kerr effect reduces the diameter of the ongoing gaussian laser beam. The simulation corroborated with theoretical models confirms that the nonlinear factor of merit (NFOM) presents a maximum at 1.940μm. By varying the fluence intensity, we demonstrate the laser’s ability to engrave silicon surfaces with a series of pulses. Moreover, we also highlight the impact of TPA effects competing with the focusing Kerr effect in the ablation process, deviating from the linear power law. Our findings provide valuable insights into optimizing laser parameters specifically for drilling and dicing applications.

Due to high functional properties such as resistance to mechanical, thermal and other physical and chemical impacts, metal matrix composites (MMCs) are widely used in high-tech industries for instance aerospace, automotive, medical, chemical, etc. Modern additive technologies that produce 3D products from metal powders using lasers are unique in terms of the possibility of obtaining new materials and complex parts with the required functional properties in one manufacturing cycle. Laser Powder Bed Fusion (L-PBF) technology makes it possible to greatly facilitate and accelerate the production of such products directly from their CAD (computer-aided design) models. The fundamentals of L-PBF technology provide a significant advantage both in the development of new materials and the manufacture of products from them. However, direct formation (in situ) and application of MMCs in the L-PBF process is constrained by insufficient elaboration of the fundamentals of the formation of these materials during laser processing and incomplete knowledge of the influence of the properties and nature of the initial materials and technological parameters of L-PBF on the final properties of MMCs. The investigation of the processes of forming metal matrix composites by laser-powder bed fusion is driven by the need to ensure stable and confident properties of L-PBF MMCs materials and parts regardless of the equipment used. In this research, the fundamentals of the L-PBF process during in-situ manufacturing of MMCs from dissimilar powders having different melting points and granulomorphometric properties are considered. Preliminary numerical simulations of thermal fields for different parameters of the L-PBF process on the powder mixture have been carried out.

Research of literature dedicated to neural networks and artificial intelligence was made. The topicality of the research in this area was proven. Neural network models most using in computer vision were chosen. The possibility of using a method to detect defects during the process of direct metal deposition based on neural network application was proven. Three neural network models based on U-Net, ResUNet and VGG-16 architectures were trained. The best of three models was chosen. Goals for future researches were set.

Femtosecond lasers play a significant role in the industrial processing of metals, including cutting masks, drilling foils, texturing molds, and engraving. This research explores methods for maximizing the removal rate of metals. The highest removal rate and best quality can be achieved using pulses shorter than 300 fs and optimal laser fluence. We also demonstrate the potential of femtosecond laser polishing of laser-machined surface, resulting in surface roughness well below Sa<1 μm. Examples to be showcased include manufacturing gratings for FIR spectroscopy, drilling stainless steel, deep engraving, and polishing dies for coin minting.