Laser-based Micro- and Nanoprocessing XIX

Femtosecond laser processing in GHz- and MHz-burst mode has attracted much attention in the last years. In this contribution, we report on pump-probe shadowgraphy of glass drilling with a temporally shaped femtosecond laser beam operating in both the MHz-burst and the GHz-burst regime. We were able to measure the luminescence time of the plume in both operating regimes and compare it to the regime of standard repetitive single pulses. Moreover, we monitored the plume behavior during the drilling process of through holes.

Ultrafast lasers have emerged as the most promising tool for fabricating high-aspect-ratio holes in glass, essential for modern microelectronics. The most popular fabrication techniques based on ultrashort pulses include percussion drilling, rear-side ablation, and selective laser etching that involves aggressive chemicals. This study highlights advancements in through-glass vias (TGV) fabrication using rear-side ablation and percussion drilling with a focus on processing time optimization. We demonstrate the capability of taper-free fabrication of high-aspect-ratio holes, addressing a common challenge in subtractive laser processing. By fine-tuning laser parameters and employing optimized processing strategies, we achieve hole diameters of less than 100 μm with an aspect ratio over 1:20. Besides the rear-side ablation process, we show the influence of pulse energy and MHz burst mode on the depth of microholes fabricated in the glass. The results were achieved using a laser source generating 200 uJ energy in a single pulse and up to 400 uJ burst energy at a wavelength of 1030 nm (Jasper X0, Fluence, Poland).

Through-Glass Vias (TGVs) are crucial in semiconductor and electronics industries, enabling high-density interconnections in devices from automotive sensors to Micro-Electro-Mechanical Systems. They support device miniaturization and improve electronic package performance by enabling vertical electrical connections through glass substrates. Femtosecond laser pulses can drill transparent materials like glass with minimal thermal effects, though throughput and aspect ratios can be limiting factors. Our research investigates femtosecond laser burst modes in the GHz regime for percussion drilling of materials such as fused silica, diamond, silicon carbide, and sapphire. We found that long, well-formed channels can be produced, in some cases reaching into tens of millimeters with an aspect ratio of 1:100, outperforming conventional single-pulse techniques. These results indicate increased micromachining efficiency for TGVs and potential applications in advanced optics, biomedical devices, and beyond, demonstrating the enhanced performance of GHz burst mode femtosecond laser machining.

The increasing demand for miniaturized and high-performance consumer electronics has driven advancements in packaging solutions, including the transition to glass interposers. A critical aspect of this development is the fabrication of high-density through-glass vias (TGVs). This study presents the formation of TGVs in various glass substrates using a femtosecond laser FemtoLux 30 operating in MHz/GHz burst modes. By employing burst mode and micromachining methods such as bottom-up milling, TGVs with aspect ratios exceeding 1:80 were achieved, with drilling times as low as 350 ms. The findings demonstrate the potential of GHz burst femtosecond lasers as a high-throughput, precise solution for TGV fabrication.

We present a micro-via fabrication technology for glass materials. The technology, which is based on KrF excimer laser direct ablation drilling, demonstrates high productivity, achieving more than 1000 micro-vias per second on glass substrates using an excimer laser and a diffractive optical element (DOE). This high productivity is further enhanced by the pulse shape (time domain) of the excimer laser. Extending the laser pulse width from 32 ns time-integrated square (TIS) to 130 ns TIS is shown to increase the ablation rate by a factor of 2.2. We analyzed and identified the mechanism of this productivity enhancement by observing the emission light during ablation using a high-speed spectrometer and a high-speed camera. The results demonstrate that the combination of excimer laser pulse formation and DOE technologies enables high-productivity fabrication of fine micro-via holes for high-performance advanced packaging.

For the advance of VR/AR devices, development of high resolution micro display (OLEDoS) is indispensable. Accordingly, RGB OLED patterning requires a high resolution and precision shadow mask for OLED thermal deposition. To avoid fabrication difficulty of high precision mask, white OLED technology without patterning has been developed but still the increase of leakage current between pixels when they are turned on and off become serious. In general, specially designed and manufactured masks are required to realize above 3,000 ppi high-resolution display in structured OLED material deposition. In this study, we developed direct laser patterning IR-fs optical system operating in MHz and GHz burst modes and evaluated its capability for precise micro-drilling of alumino-borosilicate glass materials. The fine hole-shaped pattern is produced at a minimum of 5µm pitch level for about 0.6 inch area without sacrificing the glass strength. It is expected to contribute to the high precise manufacture of ultra fine mask (UFM) using thin glass platform corresponding to micro displays in the future.

Recently, there has been growing interest in GHz burst mode femtosecond laser pulses, which are characterized by a series of pulse (intra-pulse) trains with an extremely short pulse-to-pulse interval of several hundred picoseconds. The GHz burst is expected to be a superior tool to achieve high quality, high speed, and high efficiency as compared to the conventional irradiation scheme of fs laser pulses (single-pulse mode). We have revealed that linearly polarized GHz bursts can create lattice-like, 2D laser-induced periodic surface structures (LIPSS), exhibiting distinct geometries from the stripe-patterned 1D-LIPSS formed by the single-pulse mode fs laser pulse irradiation. It’s known that the circularly polarized single-pulse mode fs laser pulses can produce dot-patterned LIPSS on various solid materials. This study explores the potential of creating novel surface nanostructures by using the circularly polarized GHz burst mode fs laser processing and investigate their functionalities.

Surface roughness is crucial for various applications like injection molds for optical components, medical implants, and additively manufactured parts. Burst laser polishing is an advantageous technique as it allows precise and controlled depth material modification. During laser irradiation, the molten material flows from peaks into the valleys due to surface tension, as a result smoothening the surface. The idea of this work was to test the GHz burst capabilities to smooth the surfaces of metals and semiconductors. In the case of silicon wafer polishing, the surface roughness Sa of the initial non-polished wafer was reduced more than three times by multiple scans. The polishing effect was clearly visible due to increased reflection of the wafer surface. In the case of stainless steel polishing, the GHz burst mode was able to erase the laser-induced periodic surface structures (LIPSS), which were formed during conventional single-pulse laser ablation. This technique expands the applicability of ultrashort pulse technology in manufacturing areas where mirror-like polished surfaces are required.

Laser processing with GHz burst mode of green wavelength fs laser can significantly improve the ablation efficiency of copper (Cu) even at much smaller number of intra-pulses. We demonstrate superiority of the green wavelength (515 nm) GHz burst mode over the IR wavelength (1030 nm) for a higher performance of Cu ablation due to lower reflectivity. The experimental results agree well with simulation, indicate that by using the burst mode of fs laser at the 515 nm wavelength and the intra-pulse repetition rate of 4.88 GHz, the Cu ablation efficiency is improved by a factor of 2.8 for 20 intra-pulses compared to the conventional single-pulse mode. The simulation results using two-temperature model suggest that the subsequent intra-pulses in the GHz burst could interact with Cu melted by the preceding intra-pulses, leading to the enhancement of ablation efficiency.

Striking the right balance between high-energy and high-power density, process dependability, and economic factors presents a hurdle for the existing lithium-ion battery technology. In this context, the creation of three-dimensional (3D) electrode architectures with the aid of laser ablation is being explored and assessed for its influence on battery performance and potential integration into battery manufacturing. Compared to conventional two-dimensional (2D) electrodes, these designs can lead to substantial enhancements in battery longevity and high-power operation capabilities. In this study, GHz laser ablation of lithium nickel manganese cobalt oxide electrode material (>4 mAh/cm2) with a water-based binder, was studied as a function of burst mode pulse train length (20 ns – 1 µs) and average laser power for a laser scanning speed in the range of 10 to 20 m/min. An optimized GHz-ablation efficiency suitable for upscaling the 3D electrode concept was identified and demonstrated in a battery pouch cell (>200 mAh).

Various concepts for upscaling the laser structuring of electrodes for lithium-ion batteries are studied, taking into account different active materials such as lithium-iron-phosphate and graphite. High power (>400 W) GHz-burst ablation of electrodes is evaluated in terms of processing quality and efficiency and compared to the use of ultrashort pulsed laser radiation with repetition rates in the MHz regime without burst ablation. In addition, fast-charging capability of full cells with structured electrodes and with unstructured reference electrodes of similar loading were examined in a rate capability test, differential voltage analysis of the voltage relaxation and post-mortem studies to examine the fast-charging capability and lithium plating behavior.

Ultra-Short Pulse lasers (UPLs) offer significant advantages for texturing electrode collectors (CC) and structuring the electrode active layer (EAL) of both anodes and cathodes. Texturing improves electro-mechanical bonding, while structuring enhances recharging speed and electrode capacity. Here we extend these processes to Gen 3b batteries with water-based formulations to get rid of toxic solvents. Surface texturing of CC enables a 15% improvement in anode performance and prevent post-mortem delamination. High throughput is achieved with a 300W UPL and polygon scanner. Additionally, micrometric holes in EAL using a 100W femtosecond laser enhance electrode performance. Comprehensive SEM and electrochemical characterizations are presented

A key for developing high-energy and high-power lithium-ion batteries is the implementation of optimized material configurations and electrode architectures. A promising approach is the use of cathodes containing the high-voltage spinel LiNi0.5Mn1.5O4 (LNMO) as active material and enhance their electrochemical performance by implementing a three-dimensional (3D) electrode architecture created through laser ablation. A high throughput of precisely fabricated 3D electrode geometries can be realized by using ultrashort pulsed (USP) laser radiation in combination with burst mode operation. In this work, the influence of laser structuring with GHz burst mode operation is investigated for the first time for high-voltage LNMO cathodes to identify optimized laser structuring parameters.

To enhance the cycle performance of Si electrodes, we engineered and fabricated a micro-structured copper (Cu) current collector (CC) using a high-throughput femtosecond laser direct writing technique. This method addresses the significant volume changes in Si anodes during charging and discharging, which can cause delamination and wrinkling of the active material and Cu CC. By creating micro- structures on the Cu CC, we improved stress relief and adhesion, resulting in improved mechanical stability. Our full cell pouch configurations with structured Cu CC demonstrated a superior capacity retention, significantly outperforming reference cells. This precise and tunable laser micro-structuring technique may be suitable for integration into roll-to-roll processes in Li-ion battery manufacturing for improving cell performance.

Laser cutting of electrode foils is an important step in lithium-ion (Li-ion) battery manufacturing, with demanding requirements on both throughput and quality. Quality is critical because defective cuts can ultimately lead to safety hazards over the life of the battery and fast cutting is necessary to meet high-volume production demands. With such requirements, high-power ultrashort pulse (USP) lasers are a natural choice. In this work, we present results for laser cutting of Li-ion battery anode and cathode electrode materials. The anode is graphite-coated copper foil, and the cathode is aluminum foil coated with NMC. Both electrodes are double-side coated and ~100 µm thick. Using 200 Watts of infrared (IR) femtosecond pulses, high-speed cutting with excellent quality is achieved. With temporal pulse tailoring, speed is increased by up to 65% compared to a single-pulse process. Notably, NMC cathode cutting speed was found to exceed 2.5 m/s while achieving excellent quality.

Since the groundbreaking achievement of ignition and self-sustaining fuel burn at the U.S. National Ignition Facility (NIF), the field of fusion, specifically laser inertial fusion energy (IFE), has rapidly accelerated and transformed. Numerous countries are investing more heavily or initiating new fusion programs, with significant collaborative efforts from international research institutions and the private sector accelerating the path to practical fusion energy. The implications for the photonics market include an increased demand for lasers, optics, optical materials, diagnostics, and other key technologies, creating new opportunities for photonics companies and shifting market dynamics. Future challenges and strategies for achieving higher energy yields and commercial viability are outlined, emphasizing the critical role of photonics in enabling the next generation of fusion energy solutions.

The interaction of light and matter can create bonding structural and morphological changes in nano/micro-scale from the surfaces of diverse materials, sometimes even deep within them. This feature has been utilized in laser processing to produce new value for both science and industry. Recent advances in high-power, ultrashort pulsed laser and fast beam delivery technologies are rapidly expanding the possibilities of laser processing. At the same time, the number of parameters to be controlled has become enormous, which is why we have introduced Data Science. In this talk, we will discuss new data-driven laser processing utilizing high-speed data acquisition and AI data optimization for higher throughput and quality. We also aim for this technology to contribute to sustainable manufacturing and society in the future.

Optical frequency combs have revolutionized time and frequency metrology by providing rulers in frequency space that measure large optical frequency differences and/or straightforwardly link microwave and optical frequencies. One of the most successful uses of frequency combs beyond their original purpose has been dual-comb interferometry. An interferometer can be formed using two frequency combs of slightly different line spacing. Dual-comb interferometers without moving parts have no geometric limitations to resolution, therefore miniaturized devices using integrated optics can be envisioned. Dual-comb interferometers outperform state-of-the-art devices in an increasing number of fields including spectroscopy and holography, offering unique features such as direct frequency measurements, accuracy, precision, and speed.

Today, approximately 12,000 satellites orbit Earth. By 2030, estimates show numbers above 60,000. Today, we service spacecraft when absolutely necessary. By 2030’s, in-space services will be routine; refueling, repair, relocation, assembly, and manufacturing. Advances are underway to realizing this future, enabling a sustainable version will require photonics technologies.

Centimeter-sized and micrometer-precision glass structures with three-dimensional (3D) internal configurations have important applications in various fields of science and engineering such as high-throughput continuous-flow synthesis and biomimetic manufacturing. However, fabricating these structures using conventional microfabrication technologies remains a great challenge. To address this issue, we demonstrate our recent progress in advanced fabrication techniques for producing 3D large and precise glass objects using ultrafast laser volume processing. Our advancements include the creation of a 3D centimeter-scale glass hand with an encapsulated free-form glass microchannel, the production of various high aspect-ratio glass structures with large depths using a Bessel beam, the spatiotemporal modulation of femtosecond laser pulses for 3D isotropic microprocessing, and the development of low-loss optofluidic devices embedded in glass.

Cells possess the remarkable ability to generate tissue-specific 3D interconnected networks and respond to a wide range of stimuli. Understanding the link between the spatial arrangement of individual cells and their networks’ emergent properties is necessary for the discovery of both fundamental biology as well as applied therapeutics. However, current methods are unable to generate interconnected and organized single cell 3D networks within native extracellular matrix (ECM). To address this challenge, we report a novel technology coined as CELLNET. This involves the generation of crosslinked collagen within multi-chambered microfluidic devices followed by femtosecond laser ablation of 3D microchannel networks and cell seeding. Using model cells, we show that cell migrate within ablated networks within hours, self-organize and form viable, interconnected, 3D networks in custom architectures. Heterotypic CELLNETs can also be generated. Real-time calcium signaling response in normal and laser ablated or disrupted CELLNETs can also be investigated. CELLNET is agnostic of cell types, ECM formulations, 3D cell-connectivity designs, could pave the way to address a range of applications.

Both ultrafast laser assisted etching and two photon polymerization can be applied to tailor transparent material characteristics and create hierarchical tumor-on-chip configurations mimicking intravasation-extravasation metastatic environment to observe cancer cells behavior in confined spaces. Herein, each technique was employed to fabricate biochips. The former processing created hierarchical geometries with constricted channel widths of less than 1m. In such platforms we were able to observe cancer cells breaching submicrometric intravasation-like barriers while retaining their viability and proliferation activity. We have further utilized the latter processing to develop new in vitro protocols for monitoring cancer cell migration and invasion potential in tissue-like polymeric configurations, correlating the higher cell motility on collagen containing scaffolds with cell invasive potential. We propose such tumor-on-a-chip models to explore the molecular and cellular mechanisms behind cellular responses to unconventional FLASH radiotherapy schemes, with the view of applying them as novel radiotherapy modalities against radioresistant cells and deep-seated tumors.

High throughput laser processing was used to identify novel glass topologies that enable anti reflective and self-cleaning behavior. Over 10,000 unique topologies were manufactured and tested for their optical and wetting performance, with over 1,000 demonstrating improved performance in both metrics vs. bare glass. Initial screening determined the wettability and transmission of each topology and each was manufactured and characterized in a matter of seconds. Promising topologies were further tested, and demonstrated high optical transmission after artificial soiling, as well as abrasion resistance. Direct laser processing of the glass eliminates chemical processing for enhanced surface performance, and the wide variety of topologies may be re-created using other manufacturing techniques. The topologies created here may increase clean photovoltaic performance by 3%, and anti-soiling can eliminate up to 40% of additional losses.

The production of via holes for PCBs is an ever-green topic. In the past CO2-Laser have been employed for drilling via holes with hole diameters down to about 25 µm. Due to miniaturization and higher interconnect densities, the via hole size has shrunk to about 10 µm for which short pulses UV-Laser sources are now used. The next generation PCBs require even smaller interconnects at significant higher densities: 5 µm hole diameter and tens of millions of holes per PCB substrate. Hole size, quality, position accuracy and production speed have become such demanding that the upcoming industrial-level, ultrashort pulses deep UV-Lasers enter the production field. In this presentation, the current generation UV-ns, UV-ps and the newly available DUV-ps Laser drilling processes for µVia holes will be compared.

Modern microelectronics applications require processing technologies that not only provide micron and sub-micron resolution, but also the highest throughput requirements with minimal defectivity and debris generation. Classical laser processing with infrared or visible wavelengths is challenged to limit the size of the affected regions to the sub-10µm range in non-metals, even when using ultrashort pulses. Lasers with wavelengths in the UV and DUV, however, offer linear absorption in many wide bandgap materials, resulting in a massive reduction in penetration depth and a more confined interaction volume. This opens the possibility of significantly improving both resolution and quality of laser processing, while maintaining high maximum throughput due to improved efficiency. This paper presents the results of investigations into several promising microelectronics applications, including sub-micron surface structuring, high-precision laser lift-off of GaN, high-speed grooving of silicon, and the generation of quantum defects in SiC.

High-quality OLED displays are a key feature for premium mobile phones. Pico- and femtosecond UV-lasers are used to cut the shape and hole with maximized active display area, and minimal HAZ. We will present our latest cutting results and strategies to increase quality and throughput using optimized process parameters for pulse energy, pulse repetition rate, wavelength, and optical setups. In our experiments we found the laser wavelength to be the most important parameter, followed by the pulse energy. In the UV (355 and 347 nm) we achieved excellent quality cuts with HAZ between 10 and 20 µm and cutting speed well above 100 mm/s, for both, ps and fs pulses. DUV ps-pulses (266 nm) improved the cutting quality tremendously, with HAZ below 10 µm and unprecedented edge quality. We will give an outlook how DUV cutting processes could be a breakthrough for display manufacturing.

In this paper, we will present results achieved with a high-power nanosecond UV laser source to process CFRP and PET materials. A parametric study will be presented, comparing the effects of various pulses from 2ns to 20ns and evaluating the interest of burst of pulses. We will show the interest of short nanosecond pulses for high quality and high speed processing compared to classical long nanosecond pulses.

Ultrafast laser processing is a promising nanofabrication technique, yet achieving nanometric precision for sub-10 nm structures in hard materials is a significant challenge. In this report, we push the laser writing to close-to-atomic-scale, a new limit, with assistance by exploiting a threshold tracing and lock-in method. We have demonstrated with feature sizes as small as a few nanometers, i.e., less than 5 nm or λ/100. This enables the deterministic creation of single photon emitters in regular arrays with near 100% yield.

Hard crystals like sapphire have proved to be a key element in a vast range of applications including industrial, optical and aerospace research. However, attaining precision in processing them remains an arduous task due to their exceptional tolerance to high pressure and temperature. In this study, we observe the dynamics of structural and morphological changes in bulk sapphire using quantitative optical phase microscopy. The thermo-optic dynamics reveal the process of phase transformation from crystalline to amorphous and the manifestation of void inside bulk single-crystal sapphire. Furthermore, the scanning and transmission electron microscopy indicates the presence of a nano-void of around 100 nm and a thin layer of disoriented crystals at the interface of the amorphous and crystalline inside the bulk sapphire. This study will be beneficial in understanding the light-matter interaction in hard crystals and help in achieving precise control of the high-aspect-ratio volume modifications inside hard photonic crystals.

Pulsed UV laser irradiation of glass leads to stress in the near surface material. The introduction of such stresses by nanosecond-pulsed lasers at fluences in the melting regime is based on the temperature gradient mechanism. The material at the surface melts, expands and contracts during solidification, resulting in tensile stress. This stress influences the shape (local curvature) of the glass sheet. By line-patterned irradiation with periods of about 10 µm, strongly anisotropic curvatures indicating anisotropic stress can be induced. With suitable utilization of these stress states, the induced macroscopic deformations can be used in the future for figure correction to obtain high precision optics or even for manufacturing freeform-optics.

We have developed a novel method to couple free-space light into a waveguide using laser-based micro-processing techniques. The resulting system is entirely monolithic. The coupling lens and waveguide are fabricated from the same material (fused silica) ensuring that no free-space alignment is required. The waveguide is written via femtosecond-laser writing and the coupling lens is written using a laser ablation and reflow process. Markers are used to ensure alignment between the two components during fabrication process. This approach opens up opportunities to deploy integrated optical systems in harsh environments with tolerance to mechanical shock.

We present time-resolved complex optical electric-field imaging of femtosecond laser ablation, covering ten orders of magnitude in timescales, from sub-picoseconds to milliseconds. This method integrates two probe branches in a pump-probe digital holographic imaging system: a femtosecond probe pulse for measuring dynamics from sub-picosecond to nanosecond and a nanosecond pulse from nanosecond to millisecond. We developed a stable common-path interferometer for complex-field imaging, achieving a phase precision of 1.5 mrad. Using this system, we investigated the surface processing dynamics of a BK7 glass substrate induced by a 257-nm femtosecond pump pulse. Our measurements revealed dynamic variations in amplitude and phase images over the entire timescale, allowing observation of subtle phase changes such as crater rim formation and thermal diffusion. This new imaging system advances the study of laser material processing across multi-timescales.

The fabrication of full color microLED displays with a small pixel pitch represents a technological challenge. Halide perovskites are materials with interesting optoelectronic properties and a higher absorption coefficient, which could in theory address color conversion for pixel pitches of 1 µm. In this study, inorganic halide perovskite thin films are manufactured using Pulsed Laser Deposition. Their potential for use in color conversion layers is investigated. Their optical properties are measured by photoluminescence. The color emitted is pure and the emission is uniform on 200 mm wafers. Photoluminescence under constant optical flux indicates a high stability of the color convertors. The high absorption coefficient measured confirms they could be used for microLED with smaller pixel pitches. These properties indicate that pulsed laser-deposited inorganic halide perovskite thin films are promising candidates for microLED color conversion, especially for pixel pitches of 1 µm or below.

This study introduces a method to optimize the macroscopic shape of 3D glass components with microscopic components, fabricated using Selective Laser-induced Etching (SLE). SLE involves two steps: Laser modification and chemical etching. The challenge with fabricating large glass components is that longer etching times lead to deviations from the target geometry due to the etching of pristine material. To address this, the chemical etching step is simulated using a reaction-diffusion cellular automata system modeling the etching of fused silica by KOH. The simulation is calibrated and validated with measured etching rates and time series data of various geometries, also considering changes in local KOH concentration. An example optimization is demonstrated on a spray-burner nozzle with both macroscopic and microscopic features, adapting the initial model to ensure the final component closely matches the target geometry. This method enables precise geometrical optimization for large-scale glass components in SLE processes.

Selective Laser-Induced Etching (SLE) is a micromachining technique specifically applied to transparent materials like various glasses, involving laser irradiation to locally modify the material followed by wet chemical etching for selective material removal. We adapt the SLE method to optimize femtosecond laser patterning of fused silica molds for casting polymer-based high aspect ratio microcavities with enhanced light absorption properties. Surface reflow via CO2 laser polishing addresses issues of surface roughness and polymer adhesion, impacting surface smoothness and reflectance. Our findings demonstrate SLE's potential for efficient fabrication of intricate microstructures for applications of flexible, dark surfaces.

Selective laser etching (SLE) is a promising subtractive manufacturing technology to create integrated optical structures in glass. Previous studies showed that the surface quality is sufficient for optical applications if the right process parameters are known and that this technique can be used for structuring different types of glass. The process itself induces stress inside the material which limits the distance between single structures inside the glass. We present a detailed investigation which laser parameters are affecting the applied stress as well as the effect of a subsequent annealing step before and after etching. Optimized process parameter enables the fabrication of dense packed photonic and opto-fluidic chips, i.e. for sensing application.

Significant progress in laser beam shaping has been driven by scientific and industrial demands. Nondiffracting beams, such as Bessel beams, are widely used for communication, imaging, and laser microprocessing due to their self-healing and resistance to diffraction. However, controlling the elongation of an optical needle's transverse profile remains a key requirement. This study proposes using nondiffracting Airy beams and a binary phase mask to achieve this control. Performance is evaluated through numerical simulations and experimental assessments, focusing on metrics like the major-to-minor axis ratio, needle length, and stability. A flat optical element is created using geometrical phase induced by nanogratings inscribed with a femtosecond laser. The geometrical phase element's performance is validated through laser microprocessing of transparent glasses, with reported experimental results.

AI Heterogeneous Advanced Packaging Technologies have evolved quickly over the last several years and their package dimensions have increased to accommodate higher computing power and larger bandwidth. High-precision flip-chip bonding technology with minimum heat loading during the bonding process is required for these large-size packages. Minimum heat-loading is very important for heterogeneous chip packaging to minimize the impact of the thermal expansion coefficient difference between PCB substrate and chips or between glass interposer and PCB substrate. Thermal-compression bonding (TCB) technology is being tried with reasonable quality and throughput, but a long processing time for TCB becomes a bottleneck for increasing production capacity. To overcome technical issues, Laser Compression Bonding (LCB) technology and relevant assembly equipment are proposed and prepared. This LCB equipment can handle up to 100mm X 100mm size flip-chip and use the corresponding-size flat-top laser beam. The key ideas and some packaging examples using the LCB technology will be presented for large-size AI-grade advanced packages.

Laser micromachining is a cornerstone of modern manufacturing, enabling the creation of high-precision micro- and nanostructures for numerous applications. In this study, we demonstrate a breakthrough in the speed and scalability of Direct Laser Interference Patterning (DLIP) in the ultraviolet (UV) region at 343 nm. Using a high-energy, ultrafast picosecond laser source (up to 3 mJ per pulse) and an advanced DLIP optical setup, we achieved an interference area of up to 1.3 mm in diameter. This large-scale interference pattern contains over 147 000 interference maxima, allowing rapid parallel processing of stainless steel surfaces. We systematically explore the effects of pulse energy, number of pulses, and beam configuration on the resulting micro- and nanostructures, including micro-pillars (~2 µm), laser-induced periodic surface structures (LIPSS) with a ~300 nm period, and nanostructures <100 nm. The results highlight the potential of this high-throughput UV DLIP approach for industrial-scale micromachining and functionalization of surfaces.

Ultrafast laser inscription is a fabrication technology well suited to the field of hybrid photonics and has a role to play in the miniaturisation of complex optical systems. We show progress in the application of ultrafast laser inscription to the formation of on-chip gas cells for spectroscopy applications. Different annealing approaches are compared, and optical performance assessed.

The precision and efficiency of laser-enabled material processing are influenced by the laser beam and its interaction with the material. Optimizing system parameters remains complex due to the interplay between the laser source, optics, and material, requiring extensive trial and error. We present an advanced simulation framework modeling the entire laser processing system, from the laser source to the material interaction. Using COMSOL, ZEMAX, and in-house code, the simulation is calibrated with our experimental laser system. The framework accounts for various system parameters, predicting the impact of configurations on the laser beam and machining process. We simulate the interaction of a laser pulse with the material, providing insights into pulse effects. This comprehensive simulation enhances understanding of laser-matter interactions and optimizes system configurations, improving precision and efficiency. Our framework streamlines the development of laser processing systems, accelerating innovation and benefiting various industries.

We investigated the processing characteristics of PTFE films using a short-pulse CO₂ laser with controllable parameters. The laser pulse, with a spike pulse width of 200 ns and a pulse tail length of 36.4 µs, operated with either a flat-top beam or a doughnut beam at a repetition rate of 200 Hz. The lens had a focal length of 38.1 mm. PTFE films were placed at the focal point or at out-focus distances ranging from 0.00 mm to 1.80 mm. The thickness of the PTFE films ranged from 50 µm to 300 µm. The flat-top beam produced a conical hole at the focal point. With an increase in the out-focus distance and the number of pulses, the shape changed to cylindrical, and the taper angle was controlled. The doughnut beam produced cylindrical holes at out-focus distances of 0.20 mm or more, largely unaffected by the number of pulses.

The surface pretreatment of a high-performance thermoplastic (CFRP) to improve paint adhesion was investigated using a UV excimer laser at a deep ultraviolet wavelength of 248 nm. The surface analysis showed no fiber detachment or visible removal of the thermoplastic matrix, but an effective removal of residues of the organic release agent silicon. Paint adhesion tests with a solvent-reduced paint system showed good results even after long-term ageing in water or under warm and humid conditions.

This paper investigates the coupling mechanism of laser drilling with jet electrochemical machining by fluid modelling and experimental analysis,numerical simulation of flow field inside the hybrid machining head was performed,and the two-phase flow formed by the electrolyte jet and air was modeled,the mechanism of laser internal total reflection in electrolyte jet is explained.The flow path structure, pressure and flow parameters in the hybrid machining head were optimized, which effectively extended the internal total reflection length of the laser and increased the effective laser power.A series of process tests were carried out on stainless steel workpiece using different laser and electrolytic parameters, and the functions of laser and electrolytic machining were analyzed respectively in the composite machining process under different process conditions. By using suitable processing parameters, high quality micro-holes are machined with high processing efficiency.

Fiber fuse is a destruction phenomenon induced in fibers, whereas applying the drilling technique with fiber fuse in bulk glass is proposed. Previous work predicted that the moving bright spot contains a void filled with gas, surrounded by a liquid phase. However, actual phase distribution has not been observed due to the high brightness caused by heat radiation and plasma emission. In this study, we employed high-speed shadowgraph observations with near-ultraviolet backlight to reveal the phase distribution within the bright spot. Fiber fuse was induced in bulk fused silica using a 1064 nm continuous-wave (CW) laser. As a result, when the bright spot reached the glass surface, the strong emission disappeared immediately, and a void appeared. Subsequently, the weak emission around the void faded gradually, and the solidified glass appeared. This result supports the theory proposed in previous work and contributes to understanding the principle underlying fiber fuse drilling.

Cellulose, the most abundant natural polymer, has garnered significant attention in various applications due to its biodegradability, biocompatibility, and mechanical properties. Porous cellulose structures are particularly crucial in applications like filters, sensors, and biomedical materials due to their high surface area and adsorption capabilities. In this study, cellulose is thinly coated on a polyethylene (PE) film and irradiated with a 355 nm UV pulsed laser to transform its structure into a microporous form. Additionally, molecular dynamics simulations are employed to investigate the structural changes of cellulose at the molecular level during laser irradiation. The result of this study reveals trends in structural changes influenced by laser parameters. This integrated approach enhances understanding of cellulose microstructure modification, paving the way for tailored polymer films with micro-nanostructures for advanced applications.

This study investigates the fabrication of laser-induced graphene (LIG) from polyimide (PI) films using a UV pulse laser, focusing on the effects of diverse laser processing parameters. By examining specific surface areas, electrical properties, and liquid contact angles, we classify LIGs for sensor applications. Unlike previous research, we emphasize the impact of surface morphology on LIG properties. Cross-sectional analysis reveals the charge transfer complex mechanism in PI films, driven by the interaction of diamine and carbonyl groups, forming a layered structure. High temperatures disrupt imide rings in PI, leading to carbonization and porous LIG formation. Two primary mechanisms are identified: melting and vaporization. ReaxFF-based molecular dynamics simulations provide insights into thermal decomposition and carbonization at the atomic level, closely matching experimental observations. This integration of simulations with experimental data offers a framework to optimize laser processing techniques, enhancing LIG-based sensor performance and efficiency.

Polyethylene (PE) is a transparent polymer known for its high tensile strength, lightweight nature, and cost-effectiveness, making it popular for various applications including food wrappers, kitchen utensils, and insulated wires. This study explores a novel laser-assisted micro-nano foaming (LAMF) process to create porous PE composite films. By incorporating a chemical blowing agent (CBA) and utilizing selective laser processing, we achieved micro-nano channels within the 30 μm thick PE film. The process leverages the different absorption rates of PE and azodicarbonamide, a CBA, under 450 nm laser irradiation, leading to partial energy absorption and a high-temperature internal explosion of the foaming agent. Using the LAMMPS molecular dynamics program with the ReaxFF method, we modeled the resultant micro-nano structures. These porous membranes have potential applications in fields such as lithium-ion battery separators and breathable packaging materials.

We report a facile, high efficiency fabrication method for subwavelength silver gratings via direct laser writing (DLW), achieving a printing speed of 18〖 mm〗^2/h. Combined with the Moiré interferometry technique, the printed gratings can be used to measure small transverse displacement with sub-micrometer accuracy.

Advances in light control have significantly impacted fields like sensing, manufacturing, medical imaging, quantum technologies, and laser microprocessing. These advancements leverage structuring light's degrees of freedom: frequency, phase, polarization, and amplitude. As ultrashort laser sources increase power and repetition rates, efficiency in laser micromachining becomes crucial. Traditional Gaussian beams are inefficient due to their slow slopes in energy deposition and heat management. This report introduces polarization singularities to create vector flat-top beams, verified both numerically and experimentally. Geometrical phase elements are designed for high-power generation of lemon-type polarization singularities, fabricated by the Workshop of Photonics, and proven effective in applications like glass welding, thin film removal, and silicon ablation. These beams, with tunable flat-top profiles, offer better control over heat deposition and material modification, producing more precise and uniform structures than Gaussian beams. This demonstrates the potential of polarization singularities in various material processing applications, enhancing precision and efficiency.

Unfortunately, “printing” does not provide a consolidated thin film of the desired material on the flexible substrate but simply delivers the ink to the substrate, leaving the material on the substrate in the form of wet nanoparticle (NP) agglomerates or clusters. A post-sintering or a post-annealing (thermal) step is mandatory to consolidate these NPs into a film to provide connectivity and realize the desired film properties. Laser sintering is an attractive technology for creating the desired film due to its low power requirements and ability to sinter parts of printed films selectively. In continuous wave laser sintering, the optical radiation directly into the sample converts into a heat wave through a photo-thermal reaction. Here, we showcase how the thermal penetration for a focused laser signal on silver nanoparticle ink varies with substrate, scanning speed, ink thickness, spot size, and incident laser wavelength. The simulation was performed using COMSOL Multiphysics.

We are conducting research aimed at removing space debris through thrust generated by laser ablation, exploring the optimal laser for this purpose. To achieve this, we believe it is necessary to develop a simulator based on the principles of laser ablation that can estimate thrust under various conditions such as ultra-short pulses, infrared, and ultraviolet. Our research is advancing through experiments as the first step towards developing this simulator. In this presentation, we will discuss the measurement of the generated thrust and coupling factor using a Q-switched ns laser with harmonics.

Laser micro-drilling of polymer substrate is a widely used technology for multilayered interconnected and flexible printed circuit (FPC) boards. Instead of using ultrafast pulsed laser, chopped continuous-wave laser provides an advantage in greatly reduced cost of equipment and processing. In this study, detailed experimental and numerical analysis of the chopped-laser micro-drilling process on polyimide substrate was conducted. The transient temperature and structure variation during the drilling process were analyzed with a model that included heat transfer, material removal and the deformation of a polyimide film surface exposed to laser heating. The formation and morphology of the porous structure at the orifice of the drilled-hole in the polyimide film was attributed to a combination of thermal-decomposition and a thermocapillary recast effect. The maximum relative error in height deformation and diameter variation of the drilled holes was less than 10%, which demonstrated the effectiveness of the proposed model for laser micro-drilling of polymer thin films.

Processing of metallic and semiconductor surfaces by a femtosecond pulsed laser can be used to form self-organized micro- and nano-scale structures on the surface of the material. This advanced manufacturing technique, known as femtosecond laser surface processing (FLSP), is a single step process and the self-organized micro- and nano-scale structures produced by FLSP are useful in a plethora of applications, including multiphase heat transfer, catalysis, and radiative cooling. We demonstrate a logarithmic relationship between the surface roughness characteristics of the self-organized quasiperiodic microstructures on silicon produced through FLSP and the laser fluence and pulse count. Laser scanning confocal microscopy analysis is performed to measure the surface roughness characteristics of a large array of samples produced with a wide sweep of laser parameters.

Photovoltaic (PV) solar cell has been one of the most quickly developing renewable energy technologies. To upscale into the module level which will provide desired voltage and power outputs, laser scribing technology has been actively developed taking advantages over mechanical scribing, including reliable and precise scribing capabilities due to non-contact processing nature. Short/ultrashort pulsed lasers have shown favorable trends for layer specific scribing based on versatile thermal/non-thermal mechanisms selectively activated at a wide range of temporal and spatial domains. This study focuses on the manufacturing of build-integrated photovoltaic based on thin film PV architectures on two different platforms; fabrication on flexible substrates that will be attached to the arbitrary building surfaces, and fabrication of see-through patterns on conventional glass substrate in conjunction with relevant scribing mechanisms. On-going study includes efforts for larger scale manufacturing and realization of tandem solar module.

Silicon carbide (SiC) is ideal for high-power electronics due to its wide bandgap, high critical electric field, and good thermal conductivity. In this study, we deposited Ni films on a SiC substrate, used a 532 nm pulsed laser for Ni implantation, and followed with laser annealing. Techniques such as SEM, and EDS were used to analyze Ni diffusion and optimize conditions. Ohmic contact tests revealed that the initial volume resistivity (ohm·cm) was around 2.7 × 10². After applying pulsed laser implantation and sintering, the resistivity dropped to 1.483. This process greatly enhanced the ohmic contact of SiC.

We summarized our recent research progress on outdoor cable identification and length marking using laser technology compared to the conventional inkjet printing method. By inducing a photochemical effect within the polymer matrix, periodic surface features at micro and nano scales were directly created onto a standard cable jacket using an ultrafast laser system. In addition to meeting industry standards for durability, the laser marking also fulfills practical requirements such as contrast and abrasion resistance. This demonstrates the potential for high-speed laser marking on polyethylene (PE) cable without the need to reduce carbon black or add costly laser additives.

This work leverages high throughput, highly tunable laser manufacturing capabilities for the inverse design of anti-corrosion surfaces. Laser processing of a material can induce a variety of surface chemistry and topology changes that can prevent a corrosion reaction from taking place. The simplest approach to preventing corrosion is the removal of moisture, or the electrolyte that catalyzes the corrosion reaction. To analyze potential for moisture removal, each laser processed surface generated in this work was analyzed for its contact angle hysteresis, giving a dynamic look at how water interacts with each surface. Contact angle hysteresis is obtained through viewing a droplet on a vibrating surface, where the angles are measured as the surface moves below the droplet. The systems developed allow for the manufacture and analysis of a unique new surface every few seconds, with a dataset of over 40,000 surfaces created.

This study explores femtosecond laser-induced alloying of copper with amorphous silicon to enhance the stability of silicon negative electrodes in lithium-ion batteries. By addressing unstable solid electrolyte interphase formation, fs laser alloying significantly improves SEI formation and reduces parasitic reactions. Electrochemical tests confirm that fs laser surface doped Si-Cu anodes outperform pure Si and co-deposited Si-Cu alloys. This laser-based techniques technique shows great promise for advancing silicon as the next-generation anode material for LIBs.

This presentation discusses work on the laser-assisted processing and functionalization of two-dimensional (2D) layered materials. Optical nanoscopy with femtosecond resolution has been utilized to study electronic and optical behavior of nanostructures.

The electric vehicle (EV) and lithium-ion (Li-ion) battery industries enjoy a symbiotic relationship, with growth on one side mutually benefitting the other. Linking the two is the power-electronics circuitry for managing the high voltages and currents involved. For this, silicon substrates are generally inadequate and manufacturers are using more suitable materials such silicon carbide (SiC), which is challenging due to its high mechanical hardness and brittleness. Laser scribing and cutting for die singulation is important as traditional mechanical saw dicing is difficult. In this work we consider both ultrashort pulse (USP) and nanosecond (ns) pulse lasers for ablation processing of SiC wafers, with optical wavelengths ranging from infrared (IR) to ultraviolet (UV). Volume ablation rates and efficiencies are determined, and the effect of pulse bursts is considered. Absolute volume ablation rates near 50 mm3/min are achieved.

Direct laser writing is a well-established, cost-effective fabrication technique. This study investigates femtosecond laser writing on silicon carbide (SiC), a material promising for quantum photonics, sensing, and metrology. We examine the incubation effect from varying laser pulses, finding that optical breakdown is primarily due to multiphoton interactions, with an incubation parameter of 0.045, single pulse damage threshold fluence of 0.88 J/cm², and a two-photon absorption cross-section of 4.3 × 10^-60 cm⁴ s/photon. We also explore how these thresholds influence SiC’s Raman and photoluminescence spectra, revealing additional silicon phases and femtosecond laser-induced color centers.

Laser carbonization is a facile method for patterning graphitic carbon structures. Generally, patterning graphitic carbon structures with narrow line widths is difficult in laser carbonization due to the thermal effects generated during the modification process. In this study, we demonstrated that graphitic carbon structures with narrow line widths (approximately 4 µm) can be directly patterned in laser carbonization of cellulose nanofiber (CNF). Our technique enabled low-power patterning, presumably suppressed thermal effects during modification, and resulted in structures with narrow line widths. The line widths increased linearly with laser power and were readily controllable. We applied the patterned structures to Fresnel zone plates (FZP) and demonstrated that the FZP can focus laser light in the visible wavelength. The proposed method is facile and enables high-resolution patterning of graphitic carbon structures.

In this research, we detail the optimization of volume diffraction optical elements, focusing on blazed gratings and fraxicons. A recent study achieved a maximum diffraction efficiency of approximately 76% for the volume fraxicon. However, there is still potential for improvements in both mechanical design and recording strategy to enhance its competitiveness with conventional refractive elements. Our optimization approach was based on the recording of blazed gratings, which was then applied to the fraxicon. We recorded fraxicons with diameters exceeding 5 mm and tested them using a femtosecond laser to demonstrate their effectiveness in materials processing. The performance was then compared to that of a classical refractive axicon.

We present a novel method for generating cryptographic keys from laser-engraved holograms on stainless steel, designed to enhance supply chain security with a focus on industrial scalability, ease of verification, and compliance with National Institute of Standards and Technology (NIST) standards. Using laser-writing technology and off-the-shelf components for key extraction, our approach provides a straightforward, cost-effective, and reliable authentication mechanism between manufacturers and end users. By applying image processing and randomness extraction algorithms, we generate 16-kbit cryptographic keys from each engraving. To validate the effectiveness of these laser-fabricated marks, we analyze correlation coefficient maps and Hamming distance distributions between key sequences from different engravings, demonstrating minimal similarity and enhanced security. Furthermore, the generated 160-kbit key sequences successfully passed all statistical tests of the NIST SP 800-22 test suite. This method offers a practical and scalable solution for anti-counterfeiting and security in real-world applications.

Functionalizing surfaces with femtosecond laser surface processing is a growing area of research due in part to the prospects for future scalability and industrialization. The throughput of femtosecond laser-functionalized surfaces can be increased by maintaining the pulse energy of the laser and increasing its repetition rate. However, if the substrate is not able to quickly dissipate this higher average laser power, processes like microstructure self-organization may be interrupted or altogether inhibited. This study focuses on how increases in repetition rate of a laser can impact the final self-organized structures on silicon wafers and aluminum, stainless steel, titanium, and copper alloys.

Functionalization of surfaces with ultrashort pulsed lasers has received fast growing demand from the industry due to the upscaling of laser power available on the market. Nano-scale topographies generated by LIPSS and DLIP allow for controlling of the wetting properties of surfaces as well as optical and tribological surfaces, like super black or low friction surfaces. However, generating and embedding nano particles on metal surfaces has not been exploited, yet for industrial applications. It enables the coloring the surfaces by creating plasmonic resonances. With the proper choice of the laser fluence, number of pulses in a burst and lateral pulse overlap, nano particles of the noble metals like Silver and Gold are created, redeposited on the surface and embedded into a thin layer of melt phase. The control of the size of the NPs and the depth of embedding in the melt pool are the determining parameters for the absorption resonance and therefore the color. Here will present parametric study on the most influencing parameters to correlate the color tones with the NP topographies derived from SEM images.

A novel solid-state metal AM process, named laser-induced supersonic impact printing (LISIP), is developed, where solid-state metal-metal bonding is realized using the laser shock-induced impact loading, leading to three-dimensional (3D) printing of metallic materials. To explore the process capability of LISIP, experiments were systematically conducted with a focus on 3D micro-lamination of metallic structure, additive manufacturing (AM) of dissimilar materials, and printing-on-demand direct writing at various length scales from micrometer to centimeter. Steel, copper, aluminum, titanium, and magnesium alloys were used as foil and/or substate for experimentation. The process mechanisms involved in LISIP were investigated by computational modeling.

The laser-induced forward transfer process is applied as a highly flexible rapid prototype technology, to further accelerate the development of customized lithium-ion battery 3D electrode architectures. For this purpose, polyacrylic acid (PAA) was used as a suitable binder for the active materials, graphite, and silicon, and as solvent a mixture of water and glycerol. First the print quality of the developed inks in dependence on the laser and process parameters was analyzed. Finaly, multilayer electrodes were printed with silicon and graphite layers. Subsequently, they were characterized electrochemically and the results were discussed regarding the printing sequence of the layers.

Materials like fused silica and borosilicate crown glass (N-BK7) have strong covalent Si-O bonds that make them hard but brittle due to the lack of dislocations for plastic deformation. Furthermore, materials such as tungsten carbide (WC) and silicon carbide (SiC) are extremely hard and brittle materials due to their strong covalent bonds (W-C in WC and Si-C in SiC), with SiC also exhibiting sp3-sp3 bond lengths that result in tightly packed atoms, further enhancing its resistance to deformation and breakage. Machining such materials is challenging; however, Micro-Laser Assisted Machining (µ-LAM) offers a promising solution. By applying laser energy to soften hard and brittle materials locally, µ-LAM facilitates the machining process, making it feasible to shape these hard materials. This study uses a Universal Mechanical Tester (UMT) to evaluate the cutting performance of brittle optical materials such as fused silica and tungsten carbide under various conditions, with and without laser assistance.

Laser Powder Bed Fusion (LPBF) is an additive manufacturing (AM) process that capitalizes on high resolution lasers and layer-by-layer melting to produce components. The drawback to LPBF is processing time (cost) and part anisotropy (properties). Beam shaping is growing in AM as a method to improve material deposition. A “ring” laser shape has growing interest due to a wider spot size and more uniform laser intensity across the spot compared to traditional gaussian laser profiles. This ring profile enables more laser power to be deposited into the material with fewer passes, resulting in an improvement in productivity. However, the impact of this improved deposition rate has not been fully characterized. In this effort, gaussian and ring profiles were evaluated for potential productivity and material enhancements in LPBF.

Alloy nanoparticles, which are difficult to fabricate by conventional thermal equilibrium methods such as chemical reduction, can be formed through non-equilibrium physicochemical reactions by focused femtosecond pulsed laser beams into solution. In this presentation, the mechanism of nanoparticle synthesis and attempts at highly efficient synthesis for industrial applications will be described.

A method is proposed that enables laser process parameters to be optimized and controlled separately from the motion profile using position-based pulse control mechanisms. This method allows new laser processes to be extended to existing motion profiles and vice versa, decreasing the overall development time required for production-ready processes. Features are machined in stainless steel at both slow and fast velocities, without adjusting the laser parameters, to demonstrate consistent quality. The features are machined again without position-based pulse control, illustrating the interdependence of laser process parameters with profile velocity.

F2 laser emits high-energy photons of 7.9 eV (157 nm), which is much higher than the bonding energy of molecules (~4 eV). The high energy photons of F2 laser excite the Schumann-Runge continuum of O2 molecules and forms electronically excited O atoms having strong oxidative nature. The F2 laser light are utilized for various photochemical and oxidative surface modification of materials. Au is known as the noblest metal, and the high oxidation resistance is utilized for various applications. We formed Au oxide layer pattern on the Au surface by F2 laser irradiation under the ambient condition. We estimated the stability of the Au oxide layer under various condition and utilized the Au oxide pattern for protective layer of Au-S bond formation by disulfide on Au substrate surface.

This presentation will focus on the application of advanced ultrafast photonic approaches for novel materials synthesis, as well as for the development of advanced photonic techniques to probe at the nanoscale, which are issues of great interest in current materials science and engineering research. In particular, Nature inspires us in tailoring unique surface properties based on synergetic effects of chemical composition and multiscale surface morphology. We show that highly controllable, biomimetic structures, exhibiting multifunctional water repellent, anti-reflection, friction reduction and photoresponsive properties can be directly written on metallic and dielectric surfaces upon processing with femtosecond laser beams of tailored shape and polarization.

Fabrication of laser-induced periodic surface structures with near-submicron length scale can modify the optical, tribological, and surface-wetting properties of a material, and over the last decade, there has been an increasing interest in its applicability in Surface Enhanced Raman Scattering (SERS). However, controlling the LIPSS morphology to mimic functional surfaces in nature for better control and repeatability of SERS experiments could be challenging. Using double fs laser pulse irradiation, and by controlling the polarization and delay between individual pulses it is possible to vary the symmetry and size of the periodic nanostructures, which is crucial for SERS applications. In this work, we try to present a comprehensive study of the effect of interpulse delay, polarization, and fluency on the morphology of both 1D and 2D LIPSS scribed on stainless steel and Si, and the corresponding enhancement factor (EF) and the Limit of Detection (LOD) of ultra-trace concentrations of Rhodamine 6G and other chemicals drop cast on these LIPSS scribed substrates through Confocal Raman microscopy experiments.

Increasing the available energy and power of femtosecond laser has always open new applications to micro-processing. In this article we focus on the use of beam-shaping with high energy input of industrial lasers. Indeed, with the increase of the energy multiple difficulties appear for an industrial robust use. For the first time a passive beam stabilization based on Multi Plane Light Conversion technology has been implemented at 400µJ in IR. Passive stabilization is key to get more robust process implementation as it enables a stable beam-shaping in all circumstances once the system is installed and without re-alignement. This stabilization is associated with high quality square top-hat beam-shaping with a high sharpness (transition zones of 15µm for a 60µm top-hat in the processing plane) and a 0.07 beam uniformity. Process improvements compared to process without beam-shaping will be discussed, with a focus on LIPSS generation improvement.

This study examines femtosecond laser-textured fused silica, comparing high and low spatial frequency structures and focusing on their effect on optical properties related to the surface morphology. Optical assessments via bidirectional reflectance distribution function (BRDF) and integrating sphere measurements reveal performance distinctions, using both visible and near infrared (NIR) laser sources. Emphasis is placed on far-distance specular transmittance and reflectance trade-offs which are critical for optimizing antireflection techniques on optical elements.

Continuous wave interference is commonly used to produce large periodic modifications, essential for applications like lithography. However, the multistep process to produce functional devices reduced manufacturing efficiency. On the other hand, the ultraviolet ultrashort pulse laser micromachining enables precise control and repeatability of the ablation crater. We have developed a novel high-efficiency optical setup combining high-precision ablation with large modification areas. Key achievements include perfect spatial-temporal overlap which is not achieved by the other spitting techniques and will be confirmed by numerical simulations. This setup utilizes the third harmonic of a Yb:KGW laser, achieving 343 nm wavelength pulses with a 200 fs duration. With a high incident angle, we have produced gratings with a period of 800 nm in a single shot. This novel setup demonstrates excellent efficiency and versatility in manufacturing gratings across various materials.

This work presents novel 4/5-axis CNC approaches for Direct Laser Interference Patterning (DLIP) on complex-shaped parts, such as injection molds or implants. A specialized machine platform with simulta-neous translation and rotary axis capabilities, equipped with an extended-range DLIP module, is utilized. The study also demonstrates advanced monitor-ing strategies using acoustic to ensure pattern quality. Real-time adjustments to laser power based on these emissions, particularly acoustic signals, result in consistent, high-quality sur-face textures, with strong correlation between sensor feedback and topography measurements.

We present a direct fs laser interference patterning configuration, employing commercial or laser-fabricated diffractive optical elements, yielding a high-contrast, well defined excitation profile composed of periodic lines or spot arrays. High-precision patterns can be imprinted with the possibility of tuning the period from 5 µm down to 650 nm. Applied to crystalline silicon and germanium, amorphous nanostructures with sharp borders have been obtained. The obtained topography profiles demonstrate the presence of non-ablative matter reorganization processes. Applied to metal films, periodic nanostructures can be imprinted via local ablation. We present several mitigation strategies to address the problem of film delamination.

Ultrafast laser surface structuring offers a promising technique for controlling surface functionalities such as wettability, achieving a range from superhydrophilicity to superhydrophobicity on various materials. However, long-term storage in ambient air presents a stability challenge, as metals initially exhibiting superhydrophilicity tend to become hydrophobic or superhydrophobic over time after processing. Understanding the mechanisms behind this aging process and its impact on wettability is critical. This study investigates aging effects on metals structured with femtosecond lasers. It examines the roles of storage environments, surface chemistry, and morphology. A semi-quantitative model describing the aging process is proposed and aligns well with experimental observations, providing valuable insights into the interplay between surface characteristics and aging dynamics.

The advanced requirements of flexible and large-area electronics demand low-temperature, solvent-free and mask-less processing of patterns with versatile form factors. Laser-induced forward transfer of metal nanoparticle inks, followed by laser sintering, is a key technology for flexible electronics. However, challenges remain for flexible, thermally sensitive substrates. We explore laser printing and processing of Ag nanoparticle inks on sensitive substrates and non-planar structures. Key parameters such as laser repetition rate and pulse overlap are investigated. Electrical behaviour and morphological characteristics of the fabricated structures are suitable for organic photovoltaics and thin film transistors.

Tunnel oxide passivated contact (TOPCon) solar cells will likely become the most produced crystalline silicon photovoltaic architecture within the next five years. The technology relies on multiple thin films to improve cell efficiency by further reducing electron-hole recombination at metal-semiconductor interfaces. Lasers are used to remove the anti-reflection thin film layer to prepare regions of the cells for electrical contact formation (“metallization”). This process—laser contact opening or LCO—is challenging in that the underlying thin films must suffer minimal damage. TOPCon is an ideal architecture for implementing electrochemical plating metallization, which has certain advantages over conventional methods. In this work we report on the use of ultraviolet (UV) wavelength ultrashort pulse lasers for TOPCon LCO processing in concert with electrochemical plating metallization. Laser parameters selection is reviewed, and processing results are analyzed with optical and scanning electron microscopy. Complete solar cells are fabricated and performance metrics are discussed.

Ultrafast laser-induced periodic surface structures (LIPSS) represent a significant advancement in reducing hydrogen uptake during the cathodic charging of Fe-Cr alloy. This study evaluates the physico-chemical impact of low and high spatial frequency laser texturing (LSFL and HSFL) on mirror-like surfaces, which demonstrate substantial decreases in hydrogen subsurface concentration. Advanced analyses that ultrafast laser-induced periodic surface structures, despite having a similar oxide layer thickness to mirror surfaces, exhibit a significantly different oxide composition. These changes in surface oxidation induced by laser texturing play a pivotal role in mitigating hydrogen absorption. Morrobrt, Atomic Force Microscopy (AFM) also reveals that these topographical variations, influenced by skewness and kurtosis, play a significant role in reducing hydrogen permeation

In recent years, semiconductor thinning and IC probing have become crucial for detecting and preventing vulnerabilities in electronic devices. Optimizing surface quality is essential for reliable analysis but can be time-consuming due to numerous experimental parameters. Machine learning can address these challenges by analyzing complex data patterns. We developed an automatic acquisition process using a confocal profilometer to gather several hundred ablation images on silicon and steel samples. Regression algorithms and neural networks predict ablation depth, surface roughness (Sa), and large-scale surface patterns. Preliminary results show a strong correlation between predicted and actual values, validating the model's accuracy and generalizability. Future work will focus on streamlining data acquisition to enable dynamic optimizations in semiconductor processes.

This presentation delves into the integration of bayesian optimization to enhance the performance of an ultra short pulse laser ablation system. The main objective is to autonomously improve process parameters through advanced in process optimization techniques. By leveraging bayesian optimization, complex optimization loops can be created to fine-tune laser settings. The system is built on a microservices-based manufacturing execution framework, enabling seamless injection of optimization loops into the production process. Attendees will gain valuable insights into the practical implementation of bayesian optimization in laser systems and discover the advantages of using microservices to achieve autonomous process control.

In the domain of material processing, lasers offer a unique blend of precision and throughput. However, optimizing the machining recipes remains challenging due to complex laser-matter interactions. This optimization currently relies on expensive and time-consuming trial-and-error approaches. We propose an advanced modeling and simulation framework for laser-enabled material processing, leveraging artificial intelligence (AI) to predict laser-matter interactions. Our approach involves training a machine learning (ML) algorithm on a dataset of pre- and post-laser pulse surface characteristics obtained through multimodality microscopy. The ML algorithm predicts the effects of laser pulses on surfaces, considering the cumulative impact of sequential pulses and temporal spacing. This AI-enabled approach reduces the need for trial and error, offering an efficient pathway to optimized machining recipes. Our framework has the potential to revolutionize laser material processing, enhancing precision, reducing costs, and accelerating the development of machining protocols. This advancement opens new avenues for innovative applications in various industries.

In the realm of advanced manufacturing, the production of metal microstructures with precise properties is a critical challenge. Compared to time-consuming and cost-intensive traditional trial-and-error methods purely data-driven Bayesian Optimization allows to learn a surrogate model of the process based on measurements for a few statistically selected input parameters. However, for complex microstructures effects like heat accumulation or the changing surface structure during processing require a different approach. In this work we present a combination of Bayesian Optimization (BO) with reduced models to find optimal process parameters. We demonstrate that this approach can be used to efficiently compute a process strategy to generate a microstructure corresponding to an arbitrary greyscale image provided as input. This study highlights the potential of Bayesian Optimization to realize a true first-time-right production for metal structuring processes, thus reducing costs, saving time, and increasing reliability.

Predicting the outcome of ultrafast laser ablation based on laser and system parameters, or narrowing the experimental parameters for optimization, can significantly reduce development time and enhance the efficiency of new laser applications. While the Two-Temperature Model (TTM) traditionally fits data with few adjustable parameters, it faces limitations for high ablation depth, high speed processing, non metallic materials. Machine learning (ML) techniques can predict diverse ablation results and optimize process strategies without prior knowledge of the physics involved. However, ML requires substantial data for effective training, which is often costly and time-consuming to acquire. This study uses two small datasets to compare ML and TTM, evaluating their predictive power, generalization capabilities, and the impact of dataset size. We aim to assess whether ML can serve as a viable, more adaptable alternative to traditional models.