This PDF file contains the front matter associated with SPIE Proceedings Volume 12409, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

Selective Laser-induced Etching (SLE) is a manufacturing process which enables the fabrication of three-dimensional parts from transparent materials with unique freedom of geometry and high precision. First, the outer contour of the part is inscribed in the material using focused ultrashort pulsed laser radiation. Second, the modified design is exposed from the bulk material using wet chemical etching. We analyze the possibility of using SLE for the machining of next generation fused silica ion traps suitable for quantum computing. Such ion traps require an enhanced functionality in combination with reduced error sources and a reproducible manufacturing process. Ion trap designs with three-dimensional features in the micrometer regime are developed to meet these requirements. Challenges of the SLE process arising from the ion trap design and its dimensions are discussed. Different process strategies to fabricate single ion trap components as well as complete ion traps are examined. We demonstrate that next generation ion traps can be machined using SLE and outline the way towards a fabrication on wafer level.

We demonstrate for the first time ultrafast laser welding in the silicon–metal and silicon–silicon configurations, with focused infrared picosecond pulses. This achievement relies on accurate characterizations of filamentation in silicon with nonlinear propagation imaging. In the silicon–metal configuration, precompensating for the nonlinear focal shift prior to the welding yields bonding strengths > 1 MPa. By combining this filament relocation technique with metallic nanolayer deposition at the interface to exalt the energy deposition, similar bonding strength values are obtained in the silicon–silicon configuration.

In the last two decades quartz has become a relevant material for sensing technology since it has been used for realization of various devices, such as Quartz Crystal Microbalance (QCM) or Quartz-Tuning-Fork (QTF). Micromachining of quartz can be realized through various techniques, such as diamond cutting, lithography, wet and dry etching, ion beam etching and Ultra-Short-Pulsed-Laser (USPL) processing. At the state-of-the-art USPL has been efficiently applied to quartz micromachining, e.g., for drilling and stealth dicing. In this study, the influence of the incubation effect and the repetition rate on USPL ablation threshold of quartz was systematically investigated. The multi-pulse ablation threshold of quartz was evaluated using 200 fs laser pulses at a wavelength of 1030 nm, at three different repetition rates, i.e., 0.06, 6, 60 and 200 kHz. Results show a strong decrease in the multi-pulse ablation threshold with the number of pulses N, as a consequence of the effect of incubation during the fs-laser ablation. Conversely, the influence of the repetition rate on incubation is negligible in the investigated frequency range. A saturation of the threshold fluence value occurs at number of pulses N > 100 and this trend is well fitted by an exponential incubation model. Using such a model, the single-pulse ablation threshold value and the incubation coefficient for quartz have been estimated. This investigation represents a first step towards the micro- and nano-texturing of quartz crystal for tailoring its mechanical, electrical, and optical properties.

We present an optical concept and adapted ultrashort pulsed laser parameters for a precise cleaving process of flexible ultrathin glasses. To this end, non-diffracting beams with tailored transverse intensity profiles generate asymmetric type-III-regime modifications along the entire substrate thickness. These laser-induced material changes not only show advantages in cutting but can also improve the bending properties of these flexible glasses when arranged in a specific manner. During the relative movement of the workpiece to the processing optics, crack connection occurs between the specifically aligned modifications only, which considerably facilitates glass separation and increases yield.

Increase in modification strength induced by ultrafast laser writing at high scanning speed in silica glass is demonstrated. Counterintuitively, despite lower energy density, stronger modification is produced, which is beneficial for 5D optical data storage.

Ultrashort-pulsed laser illumination focused inside a diamond converts sp³-bonded diamond to sp²-bonded amorphous carbon in the vicinity of the focal point and changes the color to black. A wire-shaped modified region is fabricated by scanning the laser focus toward the laser source in the diamond. Volumetric expansion by converting diamond to amorphous carbon forms cracks around the modified region. In this study, diamond slicing was attempted by using cracks formed around the modified region. A near-infrared picosecond laser was focused inside a high-temperature, high-pressure diamond. The cracks fabricated under various laser conditions were observed. The plane crack was formed by lining up the wire-shaped modified regions next to each one. During the fabrication, a high-speed polarization camera was used to observe the stress distribution around the modified region and in the adjacent wire-shaped modified region. The crack propagation was estimated by observing the stress distribution in situ. The kerf loss in the slicing process was estimated by observing the cross section of the cracks from multiple directions. These results demonstrate that plane cracks suitable for slicing the diamond were fabricated. Diamond separation was performed by applying an external force to the plane cracks.

Smart surface functionalization by laser-made micro and nanostructures is a suitable tool to maximize the value of a product and enable new properties for common materials. Despite the recent progress, the capacity to produce micro and nanoscale surface features over large areas represents a significant challenge in terms of production technology, throughput and cost, especially for components with a complex 3D geometry. In this work, we introduce multi-beam technologies able to efficiently micro/nanostructure metallic moulds with the ability to transfer micro/nanoscale morphology to complex 3D polymeric components via mass production techniques such as injection moulding. Moulded samples with replicated structures demonstrated advanced functional properties, including increased contact angle by 27°, bacteria reduction by 99.8% and decreased friction coefficient by 66% compared to the reference sample.

In laser drilling, one challenge is to achieve a high drilling quality in high aspect ratio drilling. Ultra-short pulsed lasers use different concepts like thin disks, fibers and rods. The slab technology is implemented because of their flexibility and characteristics. They bring together both advantages and deliver high pulse energies at high repetition rates. Materials with a thickness > 1.5 mm demand specialized optics handling the high power and pulse energies with adapted processing strategies, integrated in a machine setup. In this contribution, we focus on all the necessary components and strategies for drilling high precision holes with aspect ratios up to 1:40.

Laser-processing the inner surfaces of 15 m long vacuum pipes installed in the LHC aims to create a nanostructured functional surface with low Secondary Electron Yield (SEY). The experimental system to treat the vacuum pipes in-situ, including a 532 nm picosecond-laser, a 15 m long optical fiber, and an inchworm robot, will be presented. The laser-induced generation of micro- and nanostructures reduces the SEY of the surface. To optimize the surface treatment, the processing parameters were varied, and different scanning patterns applied. The variation in ablation depth, surface topography and composition correlate well with changes of the SEY.

The use of ultrafast Cylindrical Vector Vortex beams in laser-matter interaction permits to harness new ablation features from inhomogeneous distributions of polarization and beam energy distribution geometry. As a consequence, the ablation process can yield higher ablation efficiency compared to the conventional Gaussian beams. Cylindrical Vector Vortex beams prevent surface quality degradation during ablative processes. When processing stainless steel and titanium, the average surface roughness obtained by deploying Cylindrical Vector beam is up to 94% lower than the Gaussian case, and the processing efficiency is 80% higher.

Surfaces with high directional electromagnetic absorption or emission in the infrared (IR) region of the electromagnetic spectrum have numerous potential applications, however many of the relevant surfaces suffer from extremely narrow bandwidth and/or polarization dependence. Here we demonstrate broadband directional emissivity in the mid-infrared range of 7.5 to 14 μm, that is not dependent on polarization. This was achieved with angled micro-scale structures that are overlaid with nano-scale features on stainless steel 304 produced using an emerging fabrication technique known as femtosecond laser surface processing (FLSP). FLSP is an advanced surface functionalization technique that produces hierarchical micro- and nano-scale quasi-periodic surface features in a single laser processing step. Here we report a surface with peak emission for an angle of 55° using FLSP to create fin-shaped micro- and nano-scale surface features that are tilted at a 55° angle. Cross sectioning of the fin-shaped structures using focused ion beam milling was performed to understand the morphology and subsurface microstructure. Cross-sectional images and energy dispersive X-ray spectroscopy analysis show the structure consists of a thin redeposited oxide layer and the bulk of the fin structure is consistent with the original stainless-steel alloy. The emission results are verified by full-wave electromagnetic simulations which consider all the diffraction-orders performed utilizing the finite element method software, COMSOL Multiphysics, that predicts with reasonable accuracy the resulting directional emissivity of the laser processed surface.

Optimization of the process is a complex task, considering the large number of parameter combinations available in modern femtosecond laser sources and the need to increase the throughput by using the maximum available power. For UPS ablation of metals, the highest efficiency typically occurs along with the best quality because any excess pulse energy that cannot be converted into ablation products heats the material, resulting in high roughness. The laser fluence, pulse duration, and wavelength mainly determine the laser-matter interaction and ablation efficiency. Our latest study has shown that when these parameters are used properly, the ablation efficiency of stainless steel may increase by 50% compared to the best reference reported. We focus on the influence of pulse duration and wavelength on the ablation characteristics of metals. We show significant differences in ablation rates for pulses between 250 fs and 7 ps with detailed analysis of pulses <1 ps.

Laser technologies have always been and will continue to be a pivotal innovation driver in various high-tech verticals. Mobile displays for the looming 5G world as well as the booming e-mobility market are to a large part enabled by the laser power and precision needed to process thinnest layers and finest structures otherwise not attainable. Recently, magnetic confinement fusion has entered the zero-carbon energy roadmap due to the commercial availability of high temperature superconducting (HTS) thin film material. This new material is now available in large quantities and enables considerably higher magnetic field strengths and thus the construction of many times smaller fusion reactors able to contribute to the zero-carbon climate goal. Laser technology is at the heart of processing the game changing HTStapes for the new generation of fusion magnets.

ITO (Tin Indium Oxide) is a typical transparent conductive material which is widely used in various electronic devices. One of the challenges in next-generation electronic devices is a flexible and wearable device in ICT (information and communication technology). The cracking during bending is a disadvantage of ITO film in the application to a folding display. In this paper, we report the concept of the formation of a flexible transparent electrode based on an ITO microstructure-metal grid hybrid which has a high bending durability and the formation of the ITO microstructure-metal grid hybrid by combination of laser ablation and lift-off process.

An experimental study on selective single pulse ablation of a SiO₂/Si₃N₄-multilayer thin film system on fused silica substrate using ultrashort pulsed laser radiation with wavelengths of 343 nm, 515 nm and 1030 nm is presented. The effect of a NiCr metal interlayer and the influence of its thickness in the range of 0.5 – 3 nm on the ablation behavior are investigated. Clean delamination can be achieved in thin film systems including a metal layer. A decreasing ablation threshold with decreasing laser wavelength is observed for the dielectric materials SiO₂ and Si₃N₄. In contrast, the ablation threshold of the metal layer shows a negligible influence of the wavelength. However, a significant influence of the metal layer thickness on the ablation threshold is found, causing a decrease of the threshold fluence from 0.81 J/cm² for a NiCr layer thickness of 0.5 nm to 0.09 J/cm² for 3 nm thickness using IR laser radiation. The quality regarding the precision of ablation crater edges depends on the ablation mechanism. In the case of direct ablation due to absorption in the upper layer, a thermal effect is observed in the form of an ablation crater edge characterized by ridges of molten material. If there is a layer with a higher ablation threshold on top of the thin film stack, precise ablation with clean crater edges is caused by confined ablation due to absorption in the underlying layers.

The development of next-generation lithium-ion batteries with volumetric energy densities >750 Wh/L and gravimetric energy densities >400 Wh/kg is a key objective of the European Union’s Strategic Energy Technology Plan to be achieved by 2030. Both new materials and production strategies play an important role in the development of those batteries. Thick-film electrodes are advantageous to increase the volumetric and gravimetric energy densities alike since the amount of inactive material can be reduced. To facilitate higher C-rates during (dis-)charging in thick-film electrodes, laser generated structured are introduced, thus creating new lithium-ion diffusion pathways leading to a reduced cell polarization. Additionally, electrode wetting with liquid electrolyte is significantly improved, reducing the risk of dry spots in the electrode stack. Industry interest in implementing laser patterning of electrodes into existing or planned manufacturing lines has increased significantly in recent times. The strip speeds of electrode production are decisive for the required speeds to be realized in laser structuring. Various technical approaches can be applied to upscale the laser patterning process such as multibeam processing which can be realized by splitting a laser beam into several beamlets with a DOE. In this work, a large field scanner and a related optical lens system are combined with an ultrashort pulsed, high repetition rate, high power laser source. The ablation behavior of commercial graphite composite electrode material was investigated for upscaling using different laser patterning scenarios.

Lithium-ion batteries (LIBs) are currently dominating the electrochemical storage sector due to their excellent properties such as high energy density, high power density, and long cycle lifetime. For automotive applications, current research focuses on the merger of two concepts: (i) the “thick film concept” which enables a high energy density due to a reduced amount of inactive materials, and (ii) the “three-dimensional (3D) battery concept”, which provides a high power density with improved interfacial kinetics at mass loadings ≥ 35 mg/cm². Latter could be realized by applying ultrafast laser patterning of electrodes, which in turn includes an advanced 3D electrode design. Briefly, a rapid and homogeneous electrode wetting with liquid electrolyte can be induced, and besides a high capacity retention during long-term cyclability. Recently, various electrode designs such as line, grid, and hole structures have been reported for cathodes and anodes. However, the mass loss of those electrodes needs to be considered, since the cathode represents about 50 % of the total material costs of LIBs. Thus, the use of electrode structures with a high aspect ratio as well as a significantly reduced material removal is of great importance. In this work, 150 μm thick-film Li(Ni_0.6Mn^0.2Co_0.2)O₂ electrodes were manufactured by roll-to-roll tape-casting and subsequently structured with different pattern types using ultrafast laser radiation. Additionally, different designs were applied for laser patterning and the mass loss was minimized down to 7%. Finally, the cathodes were assembled in half-cells for studying the impact of different laser patterning designs on electrochemical performance.

E-mobility is currently one of the fastest growing industries. Electric powered vehicles are driving emission free transportation and will consequently replace conventional combustion engine vehicles. The battery industry is a key enabler of the e-mobility sector, laser processing of battery materials has emerged as a promising processing tool for improving manufacturing flexibility and product reliability at a high throughput. The processing of cathode and anode battery foils is an example where laser cutting has reached a high level of maturity and is widely implemented in production lines. The industrial cutting requirements are quite varied based on design and battery chemistry. The challenges are to achieve the highest edge quality at the highest processing speeds. Cutting with cw-lasers often leads to a large heat affected zone, particularly for coated foils, whereas pulsed lasers can typically cut with superior quality. While most foils can be cut with adequate quality with optimized nanosecond lasers, some material combinations benefit from shorter pulses in the ultra-short pulse regime. This contribution gives a general overview about different challenges in battery foil cutting, as well as a comparison between different laser parameters like pulse duration and pulse energy levels. The influence of laser parameters, spot size and working field are discussed as well as the impact of cutting strategy (e.g. single-pass vs. multi-pass).

The expansion of renewable energies is increasing the demand for affordable and enhanced energy storage systems. Here, 3D lithium-ion battery concepts represent a promising approach to improve e.g., energy and power density as well as lifetime of batteries. This work explores the potential of the laser induced forward transfer (LIFT) method as a tool for the realization of new types of 3D electrode architectures on structural and compositional level. Using a pulsed nanosecond UV laser, several parameters were examined to determine the variables affecting reliable material and voxel transfer, including laser fluence as a function of donor layer thickness and donor paste-to-substrate distances, as well as the influence of viscosity and solid content of the anode paste. In addition, a 3D anode is produced by combining laser structuring with subsequent localized laser printing with silicon-rich anode paste.

In the presented study, the use of an ultrashort pulsed laser system with high average laser power up to 300 W and repetition rate in the MHz regime in combination with multilayer coating was evaluated regarding the processing of multidimensional structured silicon/graphite anodes. Line patterned composite graphite anodes with grooves of different aspect ratios were generated by variation of laser and process parameters like laser fluence, pulse overlap, and repetition rate. The perspective of laser process upscaling is discussed, and it was shown that an increasing number of scans almost linearly increases the ablation depth, while the ablation width stays constant. The structured graphite anodes were handed over to a second coating step, in which a silicon containing slurry was coated to create an electrode architecture with spatial separation of graphite and silicon in the plane of the electrode. The quality of the multiple coated electrodes was studied to define a structure geometry in which defect-free filling is achieved in the second coating process. The filling of the electrode in the multilayer coating showed a dependence in blade gap during coating and laser-generated structure aspect ratio.

Femtosecond laser pulses with GHz burst mode, which consists of a series of femtosecond laser pulse trains with a pulse interval of several hundred ps is expected to achieve high-efficiency and high-quality materials processing that cannot be performed by the conventional irradiation scheme. In this paper, we show the results of GHz burst mode ablation of silicon and copper. We further extend the GHz burst mode to surface nanostructuring for formation of novel two-dimenional laser-induced periodic surface structures (LIPSS), two-photon plolymerization (TPP) for improvement of fabrication resolution, and laser-induced plasma-assisted ablation (LIPAA) for high-quality microfabrication of transparent materials.

Nowadays, improving processes sustainability has become a major topic for many manufacturers in metal processing industries. Next to the challenging rise of costs of raw material and tools, innovative and hard to process materials enter the market. Here, surface functionalization of cutting tools is devised as a convenient approach for reducing energy consumption as well as material losses. In this work, direct laser interference patterning (DLIP) is used for manufacturing periodic line-like structures with spatial periods of 5.5 μm on tungsten carbide. The texturing is applied on rake-flank faces of the cutting inserts, leading to texture depths up to 1.75 μm by controlling the amount of used laser pulses. Moreover, turning experiments under lubricated conditions carried out on Al 6061 T6 parts with structured and untreated tools are performed to investigate the tribological performance. In result, the used DLIP-functionalized cutting tools could effectively decrease machining forces up to 12 %. This is caused by the corresponding improvement in frictional and improved lubrication behavior at the tool/chip interface. Furthermore, the laser-processed tools generate thinner chips, which leads to a decrease in surface roughness by 31 % of the aluminum work piece. This work thus offers insight into the viability of improving cutting tools by laser surface micro patterning for upcoming innovative materials designed for improving tool wear resistance, energy efficiency and surface quality.

Use of kW class Ultra-Short Pulse lasers jointly with a suitable beam engineering strategy makes possible to achieve highthroughput production of laser functionalised surfaces. Nonetheless, the production of complex parts is still limited by several issues like the difficulty to reach certain regions where the geometry presents high aspect ratio shapes or tortuous profiles, and the need to adapt the laser processing workstation to a specific geometry. To overcome this issue, metallic moulds can be efficiently laser treated and employed to reproduce the surface morphology, and its specific properties, on a final polymeric replica. Forming process is a well-known method to produce any-shape part from metallic foils by applying specific constraints. In this work, forming of laser-treated metallic foils and the mechanical properties of the final formed functionalised parts are investigated in order to evaluate the possibility to produce laser-functionalised 3D complex products. By using a Rollto- Roll pilot line we textured stainless-steel 200 μm-thick foils by Laser Induced Periodic Surface Structures (LIPSS). The LIPSS morphology has been firstly optimised. Then, three types of mechanical tests were carried on laser-treated and untreated foils: standard tensile, fatigue and cruciform specimen tests. We measured and compared ultimate tensile strength, breaking strength, maximum elongation, and area reduction on specimens with and without LIPSS obtained from the same foil. By SEM and AFM analysis we compared the LIPSS morphology on samples subjected to mechanical tests and those just textured. For both, we evaluated the surface wettability through a measurement of the contact angle.

In this work, the influence of initial surface roughness on laser-induced periodic surface structures (LIPSS) formation is explored for titanium and stainless steel samples polished with grain sizes of 18.3μm, 8.4μm, 5μm, and 0.5μm, and lasered maintaining the same irradiation conditions. The resulting structures were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, and contact angle (CA) measurements, in order to characterize LIPSS periodicity and orientation, as well as surface chemistry and wettability. After characterization, representative structures were chosen to further explore their potential for bone implant treatment by inducing cells (MG63) and bacteria (E.coli and S.aureus) and testing for viability by resazurin assays, alkaline phosphatase activity, and SEM imaging. Results show that initial surface roughness (Ra) plays a different role on LIPSS generation for both materials, with stainless steel showing a higher dependence on Ra than titanium, however, both materials show a reduction on bacterial viability, while cell proliferation between polished and lasered samples also show an enhanced osteogenic effect.

Laser processing of material surfaces has been very known for the last five decades. Femtosecond LIPSS, are created generally on the surface, they could be classified into two groups depending on the periodicity of the structures: LSFL showing a periodicity lower than the incident wavelength (λ_l), and HSFL with a periodicity well below λ_l that could sit below the optical diffraction limit. In this paper, we show an unprecedented resolution of a noninvasive label-free optical method to observe such structures, that does not require a priori knowledge of the surface. We demonstrate that using a modified reflectance confocal microscope reflection (CMR), the characterization of HSFL(̴Λ_HSFL∽120 nm @ λ_l=257 nm) is possible and efficient. These results, pave the way toward a new, better, and more resolved optical technique to observe nanostructures below the diffraction limit.

We investigated the dynamics of LSFL (Low Spatial Frequency LIPSS) evolution on the titanium alloy surface. To create them, 12 W picosecond 1.064 μm laser with a pulse repetition rate from 50 kHz to 500 kHz was used. For different laser repetition rate (500, 150, 100 and 50 kHz), the ranges of LSFL periods and peak Fluence of pulse (F_p) for which the maximum period is reached were determined. We also determined the laser parameters at which the resulting LSFL have good quality and uniformity, regardless of the initial surface roughness.

Laser-controlled metal surface modifications are a powerful tool to obtain functional surfaces in a maskless process, allowing, among others, the coloration of metal surfaces, the formation of reflective diffractive gratings, and the friction reduction in bearings. Examples for each of the mentioned processes are shown. The formation of catalytic nickel nanoparticle arrays for the controlled growth of carbon nanotubes (CNTs) of various morphologies is one of the more recent developments. The laser-driven self-organization process on stainless steel causes a reorganization of the surface composition ending up in spatially selective controlled areas of nickel nanoparticle arrays showing a defined nanoparticle density. In a subsequent plasma vapor deposition step the desired architecture is grown. Most interesting are bundles of vertically aligned CNTs up to centimeters in length.

We report on the use of a kW USP (ultrashort pulse) laser system for high throughput industrial drilling, applied to the production of large micro-perforated panels, used for a new airplane drag reduction technique. In order to limit the heat accumulation due to the high power and maximize productivity, we parallelize the process: the beam is first split into sub-beams sent to different processing units, and then further split into multi-beams focused on the workpiece. Handling a kW USP laser beam makes it necessary to consider thermal regulation and potential damages. We discuss several design challenges, present results of a drilling study that illustrates how beam management strategies impact drilling quality and yields, and finally present the technical solutions implemented within a functional industrial prototype using a kW femtosecond laser.

The thermal accumulation effect is an important phenomenon for ultrafast laser material processing and was believed to happen only at high repetition rates over MHz. This study discovers that thermal accumulation can occur at low repetition rates in the kHz range in certain materials. It is found the threshold repetition rates required to initiate thermal accumulation are intrinsically determined by the thermal properties of the material and insensitive to ambient conditions. A simple analytical method is developed to predict the thermal accumulation threshold repetition rate, and the prediction agrees well with the experimental results.

Ultrafast lasers supplying highest average powers, pulse energies and pulse repetition rates require adequate system technology for high throughput and high quality laser processing. Depending on the application, multi-beam processing and/or high-speed scanning for fast beam deflection are required. Diffractive optical elements are used for beam splitting. Galvanometer scanners show high-performance at pulse repetition frequencies (PRF) up to a few MHz and polygon scanners provide high-speed scanning at even higher PRF for large surface processing. However, efficient line-oriented surface processing of small patterns using PRF in the MHz range cannot be achieved by existing scanning system technology. New resonant scanning systems have the potential to close this gap between galvanometer and polygon scanning with highest beam deflection speeds due to their oscillation frequencies in the kHz range and high duty cycles for all patterns. In addition to the high-speed scanning capabilities, resonant scanners can also enable new applications like ultrashort pulse laser (USPL) surface welding by moving the focused laser beam ultrafast along defined contours, inducing melting layers by heat accumulation. This publication describes the principles of high-speed processing with high power, high PRF ultrafast lasers in combination with high-speed resonant scanning systems. Potential applications and experimental results will be discussed like cutting, two-dimensional surface processing and functionalization, or welding applications. Moreover, a new approach is proposed to convert the nonlinear sinusoidal scanning of resonant systems into linear scanning by a spatially varying modulation of the unfocused laser beam.

A considerable increase in the ultrafast laser ablation rate has been reported for bursts in the GHz regime, although with controversy. We report results of the European project kW-flexiburst, obtained with a novel ultrafast laser that is highly flexible. It has an architecture that enables flexibility in terms of repetition rate (up to 15 GHz) and the number of pulses within the burst. Our recent results shine new light on different aspects of the laser processing of materials with bursts in the GHz regime, providing arguments for the actual disputation. We believe this new laser source can open new perspectives for ultrafast laser processing.

We describe how to improve micro-processing using Second Harmonic Generation of a Ultra-Short Pulse laser combined with a Multi-Plane Light Conversion beam-shaper. Manufacturing at 515nm presents advantages compared to 1030nm : extended depth of field, higher sharpness, and higher ablation efficiency for some materials. The beam-shaper provides a square top-hat with a 1/10 sharpness and an extended depth of field up to 10 times higher compared to other beam-shaping technologies. We describe process results of different metal samples: LIPSS generation with a 100µm square targeting a period down to 0,5µm and holes drilling holes of a diameter smaller than 10µm.

The requirements for the resolution of direct laser structuring are constantly growing and are now firmly in the sub-μm range. The most effective way to achieve such high resolution is the use of laser wavelengths in ultraviolet and deep ultraviolet (DUV) range. As the power of excimer and solid-state lasers continues to increase, not only indirect structuring, such as photolithography, but also direct ablation over large areas is becoming efficient. Still, efficient use of the available laser intensity is required to achieve high throughput of the nanostructuring tools. The contribution will discuss different approaches for sub-μm structuring with DUV radiation, including microscanners and proximity phase masks. The latter is a method that can provide sub-wavelength resolution while minimizing the system’s power loss. Unlike absorber-based masks that absorbs at least 50% of the incoming radiation, phase shift masks redistribute the energy with up to 90% total efficiency. Both one-dimensional and two-dimensional periodic patterns on 100 nm-scale can then be created over large areas, if illumination and process parameters are suitably chosen. The contribution will discuss the theoretical and practical limits of the technology and will demonstrate several selected applications of the technology on basis of high-power excimer and USP solid-state laser systems COMPEX and HyperRapid from Coherent.

A Welding/Cutting laser system that uses Wavelength Beam Combining (WBC) technology for semiconductor blue lasers, the specifications for are 445 (nm) regions in wavelength, 400 (W) in output power with a fiber diameter of ≤50 (μm) and 2.0 (mm*mrad) (typical) in beam parameter product has developed. It is also possible to combine multiple of these to increase the power to a multi-kW level. Using this laser light source, we tried a laser annealing experiment on a sputtered amorphous silicon film (50 nm thickness) on inexpensive glass with the line laser (4.0 (mm)×38 (μm)). The result shows a high crystallinity and full width at half maximum (cm^-1) < 7 (nm) at the peak position of 517 (cm^-1) with Raman microscope, which was high uniformity in the in the 4mm length in long axis direction.

We image individual particles flying from a thin metal target following nanosecond laser ablation from the transparent substrate side. Time-resolved imaging of the plume is performed using intensified CCD camera registering either spectrally-integrated thermal emission or Mie scattering signal from a synchronized illumination laser. Individual particles appear as streaks on the image, from which particle velocity distribution is derived. All particles are confirmed to leave the target at the same time. Simultaneous single-shot Mie/Thermal imaging allows to correlate plume structure with particle content.

Microfabrication is required to process glass materials in order to locally assign the desired optical properties. The authors have proposed a new microfabrication technique to form a metal sphere and manipulate the sphere inside glass. When a continuous-wave (CW) laser was illuminated from the glass side to a metal attached to the glass, a metal sphere was formed. The metal sphere was moved towards a light source with laser illumination in the glass. When the sphere migrates, it is accompanied by the diffusion of submicron metal particles. Hence, this technique allows the creation of doped regions of fine particles in the shape of a sphere’s trajectory. Controlling the shape of the particle-doped area to transform into arbitrary shapes enables the design of more flexible optical devices. The Soret effect could be one of the keys to satisfying these requirements. The Soret effect is a material transport phenomenon driven by temperature gradients in multiple components. However, to the best of our knowledge, there have been no studies on the Soret effect on metal particles in glass. Herein, we show that iron particles are transported inside silica glass as a result of temperature gradient. Metal-sphere migration produces a local particle-doped area in the glass. A temperature gradient was formed by laser heating the sphere under conditions that prevented it from moving. In situ observations revealed that particles migrated toward the metal sphere at a maximum speed of 0.56 μm/s.

Biodegradable food packaging gains a lot of significance for the sake of environment, and increased prohibition of using plastic package. Further, the functionality of sensing food status is in great importance because of health and environmental issues. Here, we report laser-induced graphene based on paper for smart food decay sensor. Direct irradiation of continuous-wave laser converts any type of commercially available papers into effective laser-induced graphene (LIG). Paper-based LIG electrodes have enough conductivity to be applicated as the electrical circuit with the sensibility on certain aspects. LIG electrode could detect either temperature alteration or gaseous chemical compounds that ejects from spoiling food. As a proof-of-concept, we developed the smart food decay sensor based on LIG-on-paper with detecting temperature of food and food decaying gas, which information is able to directly sent to users’ mobile devices through Wi-Fi network. Herein, we believe that the smart food decay sensor could contribute on environment as green electronics, and food safety with preservation of food.

Development of new lab-on-a-chip (LoC) devices requires an optimization phase in which it could be necessary to continuously modify the architecture and geometry. However, this is only possible if easy, controllable fabrication methods and low-cost materials are available. For this reason, rapid prototyping approaches for the fabrication of polymeric LoC are on the rise, as they allow high degrees of precision and flexibility. Here, we describe the fabrication platform of polymeric microfluidic devices, from the design (CAD) to the proof-ofconcept application as LoC for biological applications. The fabrication procedure is mainly based on fs-laser micromachining techniques. The ability of femtosecond (fs)-laser pulses to produce localized modification of the materials, thereby avoiding either debris, recast layers or unsought thermal affected zones, without restriction of the substrate materials, makes this technology particularly suitable for microfluidic device fabrication. In our work, fs-laser has been also possibly combined with other techniques, without the need for the expensive masks and facilities required by the lithographic process. The LoC devices have been realized in polymethyl methacrylate (PMMA), a low cost and biocompatible material. The fs-based smart fabrication platform has been exploited in the fabrication of disposable LoC devices for particles manipulation. In particular, a serpentine microchannel able to distinguish cancer from non-cancer cells without labeling and a fully inertial sorting 3D device have been fabricated and tested.

Femtosecond laser writing offers low-cost and straightforward photonic circuit fabrication compared to planar cleanroom silicon photonics. Here, we propose a compact and robust laser-written methane gas sensor based on a Mach Zehnder interferometer (MZI) in silica. The MZI is to be written in a 1 x 1cm bulk fused silica substrate with the sensing arm adjacent to the glass surface to allow evanescent field interaction with its environment. The optimisation of a styrene acrylonitrile (SAN polymer, n=1.56) surface film is simulated and discussed. Offering enhanced evanescent field in the sensing arm and selectivity to methane. Demonstrations of fabrication of low-stress buildup multi-scan waveguides and directional couplers is presented. The cladding layer thickness is engineered to improve the evanescent field ratio (power in sensitized SAN region to the total mode power) in the sensing arm up to 15% from previously documented laser written MZI sensors, thus overcoming limitations imposed by the low laser-induced index. Surface waveguides are written adjacent to the surface of the sample, improving previously achieved surface proximity for high index waveguides. The proposed sensor will require one writing step, one spin-coating step and the waveguide is mode-matched well to integrate with SMF-28 fibre devices. The sensitive polymer layer could easily be developed for other analytes with sensitivities estimated to be as comparable to similar devices developed on a silicon nitride cleanroom.

The thermal treatment process is essential throughout a wide range of realms, from the semiconductor wafer annealing process to the joint injuries heat therapy. The conventional devices for thermal processes are mostly consistent with rigid bodies and are thoroughly heavyweight, which causes difficulties in taking sufficient conformity with the object. Moreover, yet the development of soft heaters, it is challenging to partially vary the amount of heat from heating spaces. In this study, we developed strain insensitive, partially varying soft heater by laser-induced photothermal entanglement between particulate Eutectic gallium-indium (EGaIn) and silver nanowire (AgNW) managing the reaction followed by laser intensity. The photothermal reaction modifies the structure of the EGaIn and AgNW compound, a biphasic metallic composite (BMC), promoting the adhesion between the BMC layer and the substrate. The initial conductivity and local gauge factor are influenced by the degree of entanglement which is monitored by laser intensity among the BMC and the resultant becomes effectively insensitive to the applied strain. Thus, altering the laser conditions fabricate a monolithically programmable electrical heater, reducing the power supply unit, controller, and the number of wires and connecting parts, which easily creates problems in industrial devices. This work is expected to open a new route toward the rapid creation of a complex stretchable circuitry through a single process based on EGaIn, as substantiated by the demonstration of a laser-induced BMC stretchable heater that successfully achieves spatially selective heating at distinct maximum temperatures.

While sapphire is one of the most durable materials, its properties entail that high-precision machining, especially in the sub-millimeter regime, is still challenging. This contribution demonstrates and discusses novel femtosecond laser-based micromachining approaches for the fabrication of rotational-symmetric sapphire workpieces, specifically the generation of optical fibers by means of laser lathe of sapphire rod and the practical realization of windmill fibers. In addition, refractive index modification in planar sapphire substrates is presented to induce photonic crystal waveguides. The micromachined structures are comprehensively examined with respect to geometric fidelity, surface roughness, refractive index modification, and potential optical waveguiding properties. All micromachining approaches are done by means of frequency-doubled or frequency-tripled femtosecond laser radiation. Different laser optical setups including laser scanning head, spatial beam profilers including a spatial light modulator and axial rotatory movement of the specimen are employed for micro structuring and in-depth refractive index modifications. In particular for laser lathe, a sophisticated scanning pattern in combination with an incremental axial rotatory movement of the specimen allows for the precise diameter reduction of sapphire rods with 250 μm diameter to fibers with outer diameters of 25 μm. By supporting the workpiece with a V-groove fixture, multi-mode fibers with lengths up to 20 cm can be processed with an average surface roughness of 250 nm. Additionally, an adapted ablation scanning sequence enables the first practical demonstration of sapphire windmill fibers. Furthermore, using a spatial light modulator allows for the adaption of the laser propagation properties as to enable volume refractive index modifications with free-form arrangement. Hexagonal patterns of refractive index modifications surrounding a pristine waveguide core are fabricated and single-mode waveguiding at 1550 nm is verified. Finally, the possibility of integrating Bragg gratings into this photonic waveguide type is demonstrated.

This conference presentation was prepared for the Laser-based Micro- and Nanoprocessing XVII conference at SPIE LASE, 2023.

Improving processes sustainability to address upcoming demands in metal processing industries such as innovative and hard to process materials has become a major topic for many manufacturers. Therefore, new tool material compositions or surface coatings are continuously developed. In this context, surface functionalization of cutting tools is foreseen as a convenient approach for minimizing material losses and thus energy consumption. In this work, laser induced periodic surface structures (LIPSS) are used for manufacturing quasi-periodic line-like patterns on tungsten carbide inserts. The textured tool surfaces show low spatial frequency LIPSS (LSFL) with spatial periods of 500 nm to 600 nm as well as high spatial frequency LIPSS (HSFL) with a spatial period of ~100 nm. Furthermore, the texturing is applied on rake and flank faces of the cutting tools with different offsets to the edge between 0 and 0.2 mm. The wettability analysis reveals a decrease of static contact angles for the used cutting fluid (CIMSTAR) from 38° to 12°, suggesting an improved cooling process during the machining step. In addition, turning experiments under lubricated conditions are carried out on Al 6061 T6 parts to investigate the tribological performance. The used LIPSS-functionalized cutting tools could effectively decrease the main machining forces by 10 %, the feed force by 21 % and the passive force by 9 %. Furthermore, the laserprocessed tools generate thinner chips, which leads to a decrease in surface roughness by 31 % of the aluminum work piece.

Selective laser melting (SLM) is a combined process of melting and stacking three-dimensional products by fusing micro-metal powder using a laser. It has the advantage of manufacturing parts with complex structures with reduced production time. However, in the case of aluminum, the disadvantages of poor laser formability due to its high thermal conductivity, diffusivity, and reflectivity result in process defects such as bowling, pore, and poor surface quality. This study aims to develop a surface defect removal methodology during aluminum melting by laser processing and to enhance process automation capabilities by introducing a sensor monitoring scheme. In the laser experiments, aluminum specimens (AL-7075) with mechanical scratches were used and the level of surface defect removal during processing was classified depending on surface conditions. In addition, a PVDF-type acoustic emission (AE) sensor monitoring system was implemented to collect characteristic signals during the laser polishing of the machined surface(scratch). It was shown that the degree of surface defects removal and surface state could be effectively classified through a convolution neural network (CNN) utilizing the collected signals as input vectors.

This conference presentation was prepared for the Laser-based Micro- and Nanoprocessing XVII conference at SPIE LASE, 2023.

In this study, we have generated a femtosecond (fs), non-diffracting Bessel beam (800 nm, 1 kHz, 50 fs) of zeroth order through an axicon (IR range, 100, AR coated). We have performed laser ablation of a bimetallic alloy (50% gold, 50 % silver) in the air engaging the generated fs Bessel beam. The high-intensity Bessel beam-matter interaction resulted in the fabrication of exotic bimetallic nanostructures. Extensive field emission scanning electron microscope and atomic force microscopy characterizations were undertaken to study the nanoscale topographical formations. The fs Bessel beam-induced ablation on the alloy target, involving the beam profile imprint on a single surface spot, followed by overlapping two ablation zones, has been meticulously explored. The central lobe ablated area, along with concentric rings-ablated exotic patterns, were thoroughly investigated in the topographical characterization. In the case of the complete raster scan ablation, ladder-like periodic surface structures (with sub ~20 nm growths on the ladder steps) were observed. Energy-dispersive X-ray mapping was performed to confirm the elemental distribution in the nanostructured areas. Subsequently, these plasmonic nanostructures were utilized as surface-enhanced Raman scattering (SERS) platforms to detect traces of real-time explosives, ammonium nitrate (AN), and Tetryl (TL). The SERS spectra of AN depicted a signature Raman peak at 1043 cm^-1, whereas TL exhibited a signature peak near 1353 cm^-1. The lowest possible detected traces were 10 μM and 5 μM, for AN and TL, respectively.

Ultrafast laser-assisted etching provides a simple and flexible method for the bonding-free manufacture of glass-based microchannels with three-dimensional (3D) configurations and multiple functionalities. However, when the lengths of the required microchannels reach several centimeters, this method often suffers from manufacturing controllability due to the limitation of etching selectivity. Herein, we demonstrate our progress in 3D manufacturing large-scale fused silica microfluidic chips based on a hybrid laser microfabrication approach, which combines the merits of ultrafast laserassisted etching and carbon dioxide laser-induced melting. In this approach, extra-access ports are introduced to enhance the homogeneity of laser-fabricated 3D microchannels and subsequently sealed using defocusing carbon dioxide laser irradiation to form all-glass closed microchannels with few inlets and outlets. Moreover, we introduce some important applications of fabricated microfluidic chips.