Ultrashort Pulse Laser-assisted Sample Preparation for High-resolution X-ray Microscopy
Hardik Vaghasiya, Murilo Izidoro Santos, Hoang Thinh Nguyen , Paul Miclea
X-ray microscopy (XRM) is revolutionizing materials development, exploration, and failure analysis due to its non-destructive imaging and high resolution down to 50 nm. However, preparing cylindrical XRM samples with several tens of microns diameters poses significant challenges. Traditional methods like Focused Ion Beam (FIB) have mainly been used, which are precise but extremely time-consuming and unsuitable for high throughput. Addressing this issue, this study explores the application of femtosecond laser ablation in XRM sample preparation, emphasizing its advantages in achieving smooth, defect-free surfaces and precise material removal. Experimental results demonstrate the ability of femtosecond lasers to produce well-defined sample geometries, even in challenging materials such as metals, semiconductors, dielectrics and polymers, facilitating more accurate XRM measurements. Our findings underline the potential of femtosecond laser technology as a reliable, efficient, and versatile tool for enhancing XRM sample preparation workflows, paving the way for improved material characterization and advanced structural analysis.
Keywords: Femtosecond laser ablation, X-ray microscopy (XRM) ; X-ray microCT; Laser micromachining
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Laser percussion drilling of additively manufactured titanium parts with ultrashort laser pulses
Daniel Holder, Nathan Gabriel, Christian Hagenlocher, Thomas Graf
Additive manufacturing via Laser Powder Bed Fusion (LPBF) enables the production of complex, application-specific titanium components for industries such as aerospace, medical, and chemical processing, but the minimum feature size is limited to several hundred micrometers.
This work demonstrates the use of ultrafast laser percussion drilling (260 fs) to overcome this limitation by fabricating precise shallow dimples and deep microholes in LPBF-generated Ti64 parts. The drilling process is analyzed in three phases: initiation, deep hole progression, and through-hole formation.
Dimples as small as 50 µm with laser-induced periodic surface structures (LIPSS, ~1 µm spatial period) were obtained in the initiation phase, highlighting enhanced microstructuring capabilities. The study shows that peak fluence and pulse number are key to controlling dimple geometry, while pulse energy determines the depth progression and achievable depth of deep microholes. Through-holes of 1.5 mm depth and 110 µm diameter were achieved, corresponding to an aspect ratio of 14. The findings demonstrate the feasibility of using ultrafast laser drilling to introduce micrometer features and high-aspect-ratio geometries, broadening the applications of LPBF components in high-precision fields.
Keywords: Laser drilling; ultrashort laser pulses; microholes; additively manufactured parts; titanium
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Ultrashort pulsed laser robot system: Realization of a concept for large area 3D micromachining
Yongting Yang, Daniel Franz, Cemal Esen, Ralf Hellmann
We report on an ultrashort pulsed laser robot system, wherein an ultrashort pulsed laser is integrated on an axis of a six-axis articulated industrial robot. The combined motion of a 2D galvanometer scanner and the robot enhances the processing flexibility of 2D ultrashort pulse laser micromachining while extending the processing capabilities to true three-dimensions. CMOS cameras are mounted on the individual axes to monitor the beam center positions during or after robot movement. An adaptive beam stabilization system for beam position misalignment suppression is demonstrated to effectively reduce beam position misalignment within defined tolerances. With defining beam focus as the tool center point, the system reaches a 710 mm×960 mm×560 mm processing area. A set of selected large area 2D and 3D micromachining applications using the ultrashort pulsed laser robot system demonstrates its capability for flexible ultrashort pulsed laser processing. In addition, a real 3D ultra-thin glass cutting application highlights the system advantages on micromachining for the complex structures.
Keywords: laser robot; ultrashort pulsed laser robot; ultra-short pulse laser application; 3D micromachining
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Dirk Obergfell, Bahman Azarhoushang, Andrés Fabián Lasagni
Stainless steel alloys are an essential material in industrial applications due to their excellent corrosion resistance and mechanical properties. However, variations in chemical composition, thermal diffusivity, and microstructure can significantly influence laser processing performance. This study focuses on the impact of the energy distribution within burst trains of pulses on the ablation efficiency and surface quality of three stainless steel grades, being AISI 304, AISI 420, and AISI 316Ti. Using an ultrashort pulsed laser operation at at pulse duration of 250, rectangular cavities are produced at various fluence levels and different burst configurations, using different intraburst energy distributions. Burst mode operation, particularly with varied intraburst energy profiles, enhanced both material removal and surface finish. For example at a fluence of 9 J/cm² and a burst frequency of 5 MHz, using positive and negative intraburst slopes, ablation rates of 1.1 and 1.8 mm³/min were reached, with roughness values (Sa) values of 4.5 and 2.9 µm, respectively.
Keywords: burst mode, ultra short pulsed lasers; dynamic burst
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Crack-free large-diameter glass welding with femtosecond laser and repetitive single pulses
Manon Lafargue, Théo Guilberteau, Bastien Gavory, John Lopez, Inka Manek-Hönninger
Transparent laser welding using femtosecond pulses offers a promising solution for precise joining of glass materials. In this study, we demonstrate the successful assembly of large-diameter (20 mm), crack-free fused silica using femtosecond laser welding, without the requirement of chemical pre-treatment or adhesives. A microscope objective, with a numerical aperture of 0.26, was used to focus the laser at the interface, generating a highly localized and intense spot for precise melting of the material. Using a femtosecond laser with a pulse energy of 60 µJ, a repetition rate of 200 kHz, and a scanning speed of 10 mm/s, the spiral pattern minimizes overprocessing and reduces stop-start points, ensuring uniform energy deposition. This approach produced defect-free welds, contributing to improved mechanical resistance, as demonstrated by tensile testing. These results demonstrate the potential for transparent laser welding to be adopted for industrial applications in optics, photonics, and high-precision manufacturing.
Keywords: Femtosecond laser; transparent welding; crack-free; glass
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Direct welding of metals and glass substrates using GHz-burst femtosecond laser pulses
Manon Lafargue, Théo Guilberteau, Bastien Gavory, John Lopez, Inka Manek-Hönninger
The GHz-burst mode, a relatively new regime in femtosecond laser processing, offers a novel solution for joining dissimilar materials. Its unique way of energy deposition within materials makes it an excellent candidate for the transparent welding of metal and glass. This study investigates the feasibility of this approach, addressing the challenges posed by the differing physical and chemical properties of the materials. Experimental results confirm the potential of the GHz-burst mode by forming defect-free interfaces between fused silica and steel assemblies, attributed to precise energy deposition and minimal thermal impact. This innovative approach to dissimilar material assembly combines the best characteristics of each material, offering promising potential for advanced applications in the fields of electronics, optics, and photonics.
Keywords: GHz-burst mode; femtosecond laser welding; dissimilar materials; glass
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Ultrafast Laser Bessel Beam Interaction with Glass in Single Pulse, MHz-Burst, and GHz-Burst
Théo Guilberteau, Pierre Balage, Manon Lafargue, John Lopez, Laura Gemini, Inka Manek-Hönninger
We present a study on the modifications induced in glass by a femtosecond laser shaped into a Bessel beam, comparing three operation modes: single-pulse, MHz-burst, and GHz-burst regimes. In both the single-pulse and MHz-burst modes, the laser forms elongated, slightly tapered structures within fused silica. Post-etching with Potassium Hydroxide reveals high etching rates and selectivity, reaching up to 606 μm/h and 2103:1 in the single-pulse mode, and up to 322 μm/h and 2230:1 in the MHz-burst mode. Remarkably, the GHz-burst regime enables the direct formation of taper-free holes using a single burst of 50 pulses, without any etching. Moreover, we show a study of Bessel-beam drilling with GHz-bursts in alkali-free borosilicate glass. This breakthrough demonstrates the potential for chemical-free, high-speed drilling of high aspect-ratio holes in glass, opening new possibilities for advanced glass processing techniques.
Keywords: Bessel beam; GHz-burst mode; laser processing; dielectrics; glass; laser drilling
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Water Jet Guided Laser Turning for Micro-Drill Blanking
B. Mason, P. Butler-Smith, M. Leering, G. Slater, R. Ragueneau, S. Marimuthu
Micro-drills are an important tool in many industries, however the creation of them is challenging, especially as ever more slender tools are desired. Laser processing is a highly flexible option for manufacturing of such tools. The Water Jet Guided Laser (WJGL) is an especially attractive technology for the manufacture of tool blanks, prior to the generation of flutes and cutting geometries. This paper documents the development of the WJGL turning process for micro-drill blanking. A two-stage process is employed, with faceting and finishing steps. The main focus of this work was to understand the influence of federate, depth of cut, and number of passes during the finishing step. Various different stock and final diameters were trialed. This work shows, in high-tensile steel, geometries of under 0.5 mm diameter, and a surface roughness less than 1 µm Ra are readily achievable. The WJGL turning process has shown to be highly capable for blanking of micro-drills in preparation for further processing.
Keywords: Water Jet Guided Laser; Laser Turning; Micro Drills
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GHz femtosecond bust laser for high-quality and efficient deep milling
Roberta Ruffilli, Riccardo Conzatti, Martina Pagani, Caterina Gaudiuso, Antonio Ancona, Alessandro Greborio
High-quality and efficient cavity milling of tens of microns depth is underexplored but highly relevant in industrial applications. In this work, we present an innovative approach using a compact femtosecond GHz burst laser for cavity milling of different metals. We perform engravings at different depths (30-100 µm), systematically varying the burst parameters and analyzing the ablation efficiency and quality as the engraving depth increases. We also characterized the morphology of the engraving (e.g. edge recast and bottom cavity roughness) across different laser settings, to ensure an optimal balance between efficiency, quality and depth. Finally, we optimize the post-milling processes, such as polishing and whitening. We demonstrate that by optimizing burst parameters, it is possible to achieve efficient and high-quality milling at various depths. Furthermore, an optimized initial engraving strategy is essential for obtaining high-quality surface finishing, even at the greatest depths achieved.
Keywords: GHz-burst; fs; deep engraving; ultrafast laser processing; metals
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Glass percussion drilling with GHz-burst femtosecond lasers at 515 nm and arbitrary burst shapes
Alessandro Greborio, Riccardo Conzatti, Roberta Ruffilli, Antonio Ancona, Pagani Martina
The GHz-burst femtosecond laser regime has attracted growing interest for its applications in glass percussion drilling. In this work, we introduce an innovative GHz-burst femtosecond laser (800fs, burst energy >0.3mJ) operating at a green wavelength (515 nm), uniquely capable of generating arbitrary burst shapes. This advanced laser system unlocks new opportunities for optimizing ablation processes in glass percussion drilling. By combining the advantages of the green wavelength with tailored GHz burst profiles, we demonstrate that the interaction between the laser and the glass is significantly improved, resulting in faster drilling and higher-quality holes with smoother surfaces and absence of cracks. This approach lays the groundwork for advancing the understanding of GHz-burst laser processing and its transformative impact on glass drilling techniques.
Keywords: fs GHz-burst; percussion drilling; ultrafast laser processing, glass; crack-free holes
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Micro-welding of thin stainless steel foils using an ultra-short pulsed Laser
Samuel Weber, Mareike Schäfer, Ellen Bold, Sebastian Zimmermann, Clarissa Schönecker, Egbert Oesterschulze, Johannes L’huillier
The production of practical, miniaturized pipelines that allow liquids to flow smoothly presents numerous challenges. Usually, coatings are applied to the inner walls of the pipe. An innovative approach involves the use of high-precision laser processing. The utilization of USP laser processing is used both to create functional surfaces and to produce miniaturized pipes through a overlap welding process. In the context of the conducted investigations, results on overlap welding with two non-transparent thin foils with ultra-short pulsed lasers are presented in this study. Here, we conducted overlap welding on two 20 µm thin 1.4301 stainless steel foils using a ps laser. Insights into the optimal process parameters and the influence of sample preparation are presented. The parameters are evaluated in terms of power density, weld quality and reduced heat-affected zone (HAZ) of the welding results.
Keywords: micro-welding, ultra-short pulsed laser, overlap welding, thin stainless steel foils
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Christian Frey, Abhay Sharma, Pia Fischer, Benjamin Gerhards, Simon Olschok, Christian Hopmann, Uwe Reisgen
Conventionally, metals and plastics compete due to their differing mechanical, physical, chemical, and tribological properties. However, hybrid components that synergistically utilize the advantages of both materials present significant potential for weight reduction, functional integration, and cost savings. The production of plastic/metal hybrid components can be efficiently achieved during the primary forming process of the plastic part by back-molding thus eliminating the need for additional joining technologies using form closure through macrostructures. Macro structuring on metal components is accomplished through laser or electron radiation via repeated micro-welds (Surfi-Sculpt®). The strength of these structures can be tailored by adjusting process parameters, orientation, and geometry of the micro-welds. This study presents initial results regarding individual structural strength on stainless steel samples. It demonstrates the dependency of bending strength and structure geometry on ambient pressure as well as the increase in structural strength in welding direction. Higher energy input allows for elevated macrostructures but may reduce bending strength.
Keywords: Back-molding ; form-closure joining ; injection molding ; laser welding ; LaVa ; plastic-metal-hybrids ; Surfi-Sculpt®
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Deividas Andriukaitis, Valdemar Stankevič, Evaldas Kažukauskas, Paulius Gečys
The increasing demand for miniaturized and high-performance consumer electronics has driven advancements in packaging solutions, including the transition to glass interposers. One of the critical aspects of the development is the fabrication of high-density through-glass vias (TGVs). This article presents the formation of TGVs in various glass substrates using an industrial femtosecond laser FemtoLux 30 operating in different operation modes – single-pulse, MHz burst, GHz burst and MHz+GHz burst modes. By employing burst mode and advanced machining methods such as bottom-up milling – TGVs fabrication is possible. With specific parameter sets TGVs with aspect ratios exceeding 1:80 was achieved, with drilling times as low as 350 ms. Additionally, to address current challenges in making electric traces on substrates, it introduces Selective Surface Activation Induced by Laser (SSAIL) as a unique complementary metallization technology, enabling direct copper deposition on different materials like ceramic, plastics and most importantly – glass, for complete packaging workflows. The findings demonstrate the potential of the FemtoLux femtosecond laser as a high-throughput and precise solution not only for TGV fabrication, but also for Selective Surface Activation Induced by Laser (SSAIL) based metallization - supporting next-generation semiconductor advanced packaging solutions.
Keywords: Through glass via (TGV); Femtosecond laser; GHz burst; Percussion drilling; High aspect ratio hole drilling;
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Dominik Mücke, Cemal Esen, Ralf Hellmann
Ultrafast laser ablation has been proven to allow for the generation of micromechanical devices, micro-optics and microfluidics. To successfully transfer this approach towards an industrial level, process efficiency and stability as well as resulting parts quality have to be improved. Here we report on the reproducibility and enhanced accuracy of 2.5D ultra-short pulsed laser ablation of fused silica to structure complex optics by integrating centre recognition and height measurement within an automated machine setup and by sensitive adjustment of the applied laser parameters to optimize the ablated depth per path in multi-pass ablation processes. To exemplify the potential of these approaches, free-form optics and axicons are generated with improved geometrical and surface characteristics.
Keywords: Laserablation; Micro-Optics; Automation
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Bogusz Stępaka, Rafał Smolin, Natalia Grudzień, Yuriy Stepaneneko, Michał Nejbauer
The demand for micrometric through-holes in glass and silicon carbide (SiC) is growing, particularly in advanced packaging and power electronics. While selective laser etching (SLE) remains the dominant method for through-glass vias (TGVs), environmental concerns and process complexity highlight the need for alternatives. One option is percussion drilling, but it faces challenges such as drilling saturation due to the conical shape of the hole, microcracks, and stress. Recently, GHz burst processing has attempted to address these issues, but some fundamental limitations remained. In this study, we showcase the unexplored potential of repetitive single-pulse femtosecond laser drilling. Using optimized focusing conditions and a femtosecond fiber laser with >200 μJ pulse energy and 270 fs duration, we achieved full penetration of up to 1 mm - thick glass and fast SiC drilling.
Keywords: TGV, drilling, femtosecond laser, percussion drilling, deep drilling, glass, silicon carbide
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Soheil Alee Mazreshadi, Pol Vanwersch, Tim Evens, Sylvie Castagne
Laser welding is a precise material joining technique offering localized heating and a minimal heat-affected zone. For transparent polymers without an absorber layer, ultrafast pulses can trigger non-linear phenomena needed for welding. This study optimizes the scanning speed and fluence per pulse for welding polycarbonate using a 1.03 μm wavelength femtosecond laser. The cumulative fluence is calculated at the weld seam center and edge to determine the maximum and minimum energy per unit area, and the weld seam quality is assessed optically. Optimal results are achieved at scanning speeds of 10 and 20 mm/s with fluence per pulse of 0.38 – 0.72 J/cm2 and 0.65 – 1.14 J/cm2, respectively. Two damage regimes are identified: one caused by high cumulative fluence at low speeds (5 mm/s), and the other by high fluence per pulse (1.50 J/cm2) at high speeds (30 mm/s). These findings reveal how energy deposition shapes weld seam morphology and quality.
Keywords: femtosecond lasers; laser welding; non-linear absorption; transparent polymers; polycarbonate
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