United States

We have developed a fully automated laser processing and data acquisition machine, called Meister Data Generator (MDG), which can be used via the Internet 24 hours a day, 365 days a year. All the data taken by MDG is acquired in a database. MDG can perform grid search as well as autonomous optimization with artificial intelligence such as Bayesian optimization. Huge amount of data can be obtained by the automated processing setup, and we applied the data to build a deep neural network that works as a laser processing simulator. The input to the simulator is laser parameters, and the output is a shape of the material after processing. We have tried to make two types of simulators: shallow drilling of silicone and deep drilling of glass. The simulator created by deep learning was found to be applicable to drilling under conditions that were not included in the training data. We were able to predict drilling conditions that achieved more energy savings than the conditions used in the training data. In other words, we now have a predictive AI simulator. We are working with several companies to expand the scope of MDG technology. This simulator could be applied to microfabrication for semiconductor back-end processing.

ICALEO 2024

Autonomous Micro Laser Processing with Artificial Intelligence

laser processing simulator

micro processing

artificial intelligence

deep neural network

  #### Welcome to the 43rd annual ICALEO!

Attention laser enthusiasts, innovators, and industry leaders! Get ready to immerse yourself in the exciting world of lasers at the 43rd annual ICALEO conference. This year, we gathered in the iconic city of Hollywood, California, for cutting-edge technology, groundbreaking presentations, and unparalleled networking opportunities.
Whether you're a seasoned professional or new to the field of photonics, the 43rd annual ICALEO had something for everyone. 

#### General Chair Welcome Message

It is with immense joy and anticipation that I extend a warm welcome to each and every one of you as the General Chair of this year's ICALEO conference.

This year, we find ourselves in the iconic setting of Hollywood, serving as a fitting backdrop for the extraordinary developments in laser technology and applications unfolding in our community.

Our main sessions cover a diverse range of topics, from the intricacies of micro and nano processing to the transformative power of laser additive manufacturing. We will explore the frontiers of battery technology, delve into the intricate world of artificial intelligence, and witness the seamless integration of lasers into these realms.

For those joining us for the first time, we extend an especially heartfelt welcome. ICALEO is not just a conference; it's a convergence of minds, ideas, and innovations. Beyond the formal sessions, I encourage you to engage in informal exchanges. The spirit of discovery and camaraderie is as much a part of the ICALEO experience as the scheduled sessions.

Thank you for being a part of ICALEO 2024. Whether you are a returning participant or a first-time attendee, your presence adds immeasurable value to our vibrant community. May this conference be, this year again, a catalyst for inspiration, collaboration, and breakthroughs that will resonate in our community and beyond.

Eric Mottay<br>
Congress General Chair, ICALEO 2024


#### About LIA

The Laser Institute of America (LIA) is the professional society for laser applications and safety. Our mission is to foster lasers, laser applications, and laser safety worldwide. Serving the industrial, medical, research and government communities for over 50 years, LIA offers technical information, training and networking opportunities to laser users
from around the globe.

#### About LIA Conferences

The conferences of the Laser Institute of America are the town square of the laser community. A large and diverse group, laser professionals often find themselves disconnected from each other. LIA conferences, however, bring the university researcher, the business executive and the production floor user together under one roof for a unique and
rewarding networking opportunity.

#### Program Tracks
Below is the list of all tracks that were on ICALEO 2024 Conference.

##### Laser Additive Manufacturing
* The Laser Additive Manufacturing (LAM) track is a forum to explore the latest innovations and research in laser-based additive manufacturing (LAM). The Laser Additive Manufacturing track focuses on diverse topics, including laser-based powder bed fusion (PBF-LB), directed energy deposition (DED), and other emerging techniques revolutionizing modern manufacturing processes. From materials science to process optimization, from design innovation to industrial implementation, this track connects researchers, engineers, and industry leaders to exchange insights and share breakthroughs in laser additive manufacturing.

##### Laser Materials Macroprocessing
* The Macroprocessing track comprises some of the most productive laser processing applications. Although these applications have been broadly adopted, researchers and industry are persistently innovating to provide new techniques and novel technologies to advance macro materials processing. The attendees will share and discuss those exciting achievements of their research with peers in these macroscopic specialized sessions.

##### Laser Materials Microprocessing
* The Microprocessing track will consist of papers and talks featuring a wide spectrum of applications and innovative equipment for materials processing in microscales with a strong focus on processes with Short and Ultrashort Pulsed Lasers. The presentations will introduce the latest and greatest advancements in their respective fields, presented by world-leading companies and research organizations. This year we will have talks around the headlines of “Beam shaping”, “Glass”, “Surface processing” and “Drilling” between other topics.

##### Frontiers in Laser Applications
* The Frontier in Laser Applications (FLA) track explores recent, cutting-edge applications of lasers, highlighting innovation at the transition of research and industry. The track has included presentations from a variety of fields: Novel 3-D Printing, Advanced Manufacturing, Laser Manufactured Devices, and Frontiers in Laser Processing. The sessions under the Frontier in Laser Application track promise to bring diverse and unique perspectives from real-world applications across laser manufacturing.

##### Laser in Battery Manufacturing
* Electrification is crucial to address global environmental challenges. The laser plays a key role in most manufacturing steps in battery production with all possible laser applications from ablation, structuring, welding, cutting, and marking. Further improvements in the batteries’ power densities, fast charging properties, and yield in battery production are related to photonics and, thus, lasers. We will hear and discuss the latest developments in research, development, and industrial applications. Join us for this year’s Battery Track.

##### Artifical Intelligence in Laser Processing
* The track ‘Artificial Intelligence in Laser Processing’ at ICALEO 2024 explores the fusion of AI and laser manufacturing. Discover cutting-edge research on optimizing laser processes and enhancing manufacturing efficiency. Explore AI’s diverse applications in parameter optimization, quality prediction, real-time process monitoring, and control. Join us to unlock the potential of AI-driven solutions revolutionizing laser materials processing, delivering unprecedented precision, productivity, and innovation.
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Attention laser enthusiasts, innovators, and industry leaders! Get ready to immerse yourself in the exciting world of lasers at the 43rd annual ICALEO conference. 

technical paper

Residual stress is an important factor in manufacturing, including laser processing, and ignoring it can lead to product defects. This study presents a new deep learning approach to predict critical characteristics of laser-irradiated carbon steel, including thermal residual stress. The core of this study, a generative adversarial network (GAN), acts as a surrogate model, enabling more efficient utilization of computationally expensive simulations to generate the desired output. The GAN model is trained using data generated by numerical simulation. Three key laser processing parameters are taken as input: laser power, beam diameter, and irradiation time. Based on these inputs, the model predicts various properties of the laser-irradiated carbon steel throughout the process and after cooldown including residual stress. This deep learning model effectively captures the complex, non-linear relationships between laser parameters and process outputs. The model produces very fast results when compared to the traditional simulation, while the results are accurate. The model exhibits exceptional performance, achieving high R-squared values ranging from 0.975 to 0.999 across various predicted properties. The result demonstrates the effectiveness of the proposed deep learning approach for predicting laser processing outcomes in carbon steel. It facilitates efficient exploration of residual stress and melt pool evolution by enabling rapid evaluation of different laser parameter settings. Furthermore, this study emphasizes the benefits of utilizing a hybrid loss function for improved optimization of deep learning models.

Generative adversarial network (GAN)-based Prediction of Thermal Residual Stress and Melt Pool Characteristics in Laser Processing of Carbon Steel

CNT composites have been used as bipolar plates in hydrogen fuel cells due to their high corrosion resistance, chemical stability, and high strength. However, due to the low forming elongation of CNT composites, channels were mainly manufactured through milling process. There are problems with low processing precision and damage due to vibration and tool wear that occurs during milling process. Non-traditional laser processing performs non-contact processing, which can solve the problems of tool life and vibration. Furthermore, laser processing is well-known for its advantages of high precision, fast processing speed, and suitability for complex processing tasks. Consequently, research has been conducted to utilize laser processing for fabricating microchannels. Likewise, it is expected that microchannels can be processed in graphite materials using lasers, and thin separators can also be manufactured. However, research on fabricating microchannels in graphite materials have not been conducted. Therefore, this study conducted research to manufacture channels and bipolar plates in CNT composites using a nanosecond pulse laser. Channels with a width of 1.2 mm were fabricated by irradiating lasers parallelly, and the effect of parallel irradiation intervals was observed. After laser irradiation, the change in surface chemical composition was analyzed using X-ray photoelectron spectroscopy (XPS), and changes in surface resistance and wettability of the laser-processed area were measured. Finally, the feasibility of using laser processing to manufacture separators for CNT composites was examined.

A Study on the Fabrication of Channels and the Bipolar Plate in CNT Composites Using a Nanosecond Pulse Laser

Silicon Carbide (SiC) materials are increasingly used in electronics applications requiring high and dynamic voltage, current, and switching.  Largely driven by increased adoption of electric vehicles, additional markets include photovoltaics, LED lighting, and general power storage and transmission. In these and other areas, manufacturers are finding traditional silicon substrates unsuitable for the rigors of high-power electronics, and SiC is increasingly the answer. However, the high hardness and brittleness of SiC makes it difficult to process with conventional mechanical methods and therefore non-contact laser processing is being adopted. But laser selection is not necessarily straightforward, as dissociation of silicon and carbon is known to occur at relatively low temperatures.  Hence, it is useful to consider both ultrashort pulse (USP) and more conventional nanosecond (ns) pulse laser processing. In this work, we present various results using high power USP and ns lasers for processing crystalline 4H SiC wafers.  Ablation thresholds and material removal efficiencies are determined, and the effects of using tailored burst output is explored. We find that using pulse bursts can strongly improve machining quality as well as increase throughput, with volume ablation rates approaching 50 µm3/min.  Analysis includes optical microscopy as well as scanning white light interferometry for depth measurement and surface quality characterization.

Silicon Carbide Ablation With Ultrashort and Nanosecond Pulse Lasers

Powder Bed Fusion Laser Beam of Metal (PBF-LB/M) is a leading additive manufacturing technique known for producing complex metallic components with high precision. Despite its advantages, PBF-LB/M's broader application is often hindered by its slow build rates. Traditionally, increasing laser power to enhance build speed results in high peak intensities, causing evaporation of powder material and uncontrollable keyhole welding processes that produce defects such as spatters.

This presentation introduces a novel approach using beam shaping to manage and utilize increased laser power effectively. By implementing Multi-Plane Light Conversion (MPLC) technology, we can create various optimized beam shapes, such as annular or M-shaped beams, which significantly mitigate the challenges of high peak intensities. Notably, this flexibility allows seamless switching between beam shapes, adapting to different print scenarios while maintaining quality.

Utilizing both defocused Gaussian and ring-shaped laser intensity distributions, we achieved a notable 3.3-fold increase in printing speed for nickel alloy 625, without compromising the mechanical integrity of the components, as confirmed by rigorous testing. High-speed video and advanced particle tracing algorithms have further validated the efficacy of our beam shaping strategy under varied conditions, showcasing its potential to revolutionize LPBF applications. Mechanical properties of tensile bars printed with both defocused Gaussian and ring beam will also be presented.

Increase of Theoretical Build Rate in Powder Bed Fusion Laser Beam of Metal Through Adapted Laser Intensity Distribution

Additive manufacturing of copper using laser powder bed fusion (PBF-LB/M) enables the production of highly complex components. However, the processing of copper by means of near-infrared laser radiation is challenging due to its absorptivity of only 5 to 20 %. Using a keyhole welding process with a Gaussian intensity distribution increases the absorptivity to up to 53 % due to multi-reflection. This enables the production of components with a density larger than 99.5 % and electrical conductivity larger than 90 %IACS, but this type of welding leads to keyhole porosity due to keyhole instabilities. One way of counteracting is the use of a heat conduction welding process. However, due to the Gaussian intensity distribution, it is not possible to supply sufficient energy to eliminate lack-of-fusion porosity and concurrently avoid the formation of a keyhole. Ring-shaped beam profiles have proven their advantages in stabilizing the PBF-LB/M process with a tendency towards higher laser power, but pure copper has not yet been processed in this way. Therefore, this study investigates the potential of three ring-shaped beam profiles to produce specimens with a density of more than 99.5 % and their respective electrical conductivity using a laser power of up to 1,300 W. In order to understand the underlying welding process, the weld geometry of single-tracks is analyzed. Specimens with a density of up to 99.77 % and an electrical conductivity of up to 101.62 %IACS are produced, whereby the material properties and welding regime depend on the selected ring-shaped beam profile.

Laser Powder Bed Fusion of Pure Copper using Ring-shaped Beam Profiles

The present battery production process reaches only a low yield rate in the range of 75 to 90 percent. The complete manufacturing process includes 250 single process steps. Many of these process steps are based on the application of laser beams. The application specialist look as of today just on the point of interaction of the laser beam and assume a constant perfect quality of the workpiece. Online monitoring systems usually just monitor the weld area and don't take variations in the process steps before into account. This paper takes the variation of all process steps into account. The quality reached of many production steps, can get analized by photonic based sensors. In order to increase the yield in battery production, the use of photonic based sensors and the use of these results in a closed loop system to react immediately is one of the possibility to avoid scrap in production. Due to the high number of process steps and interaction of each of these steps, the help of artificial intelligence algorithm are required to achieve a positive impact. The paper describes 3 process steps with a closed loop control system including a solution to rework the results of the process.

On the Way to Battery Production with Zero-Defects With the Use of AI and Photonics

Due to its exceptional dimensional stability in harsh thermal conditions and excellent mechanical and optical properties, Corning ultra-low expansion (ULE®) glass is the material of choice in many high-demanding fields such as aerospace, astronomy, and advanced optics. This material has recently attracted renewed attention with the advent of femtosecond laser technology, with a particular focus on the interaction of ultrafast pulses and the material itself. Phenomena like the formation of self-assembled nanogratings and their thermal stability as well as the darkening of laser-affected zones have then been characterized. This paper presents how to exploit femtosecond selective laser etching (SLE) techniques to manufacture truly three-dimensional (3D) components. To demonstrate the micron-scale accuracy and repeatability of this process from the mm- to the cm-size range, various devices are designed and fabricated: fiber hole arrays with different hole densities, sizes, orientations, and shapes; and fiber V-groove arrays. Additionally, a mechanical flexural fiber mount is presented as an example of how multiple functionalities can be monolithically integrated into a single piece of glass through SLE technology. An example of a passive alignment substrate for optical components is also shown. SLE technique represents a new advancement in the field of microscale manufacturing, enabling the scalable production of custom-designed ULE® glass structures with unprecedented precision and complexity, paving the way for the miniaturized integration of highly stable components.

High Precision Microscale 3D Manufacturing of Ultra Low Expansion Glass by Femtosecond Selective Laser Etching

The increasing demand for miniaturization in electronics has driven the need for advanced fabrication techniques capable of producing through-glass vias (TGVs) with high precision, minimal spacing, and low defect rates. Ultrafast laser-based methods, particularly laser drilling and selective laser etching (SLE), have emerged as critical technologies in the fabrication of TGVs for 3D microchip stacking. Glass offers superior electrical properties, such as reduced signal loss, improved thermal stability and mechanical strength compared to traditional materials like silicon. This study presents advancements in ultrafast laser drilling techniques for TGV fabrication. We demonstrate the feasibility of taper-free fabrication of high-aspect-ratio holes, addressing a common challenge in traditional ablation-based drilling methods. By controlling laser parameters and employing optimized processing strategies, we achieve uniform hole diameters below 100 um, reaching an aspect ratio of 1:20 without chemical etching. Our research focuses on process speed optimization to enhance fabrication efficiency. Moreover, we demonstrate a high aspect ratio and high-speed percussion drilling of through holes for the glass substrates thicker than 0.5 mm. The results were obtained using <200 uJ ultrashort pulses at 1030 nm wavelength (Jasper X0, Fluence, Poland). Our findings highlight the remarkable capabilities of ultrafast laser drilling for TGV fabrication for new microchip generation.

Advancements in Femtosecond Laser Drilling Techniques for Through-Glass Vias

Femtosecond laser processing is used in a wide range of  modern technology manufacturing. Its significance is particularly evident in sectors that demand high accuracy and minimal heat effects, like microelectronics, biomedical devices, and photonics. The field has recently seen ultraviolet (UV) wavelengths become a standard in laser processing as optical coatings have become resistant to prolonged exposure to UV radiation. These features have opened up exciting new avenues in both manufacturing and scientific research.

In this study, we explore the application of novel femtosecond laser that produces a flat-top intensity distribution, at a wavelength of 254 nm (4th harmonic of fundamental 1030 nm radiation). The 4th harmonic offers unique advantages in material processing due to its position in the direct absorption regime for multiple glass and polymer materials. Our experiments demonstrate the effective ablation of soda-lime glass using this specific wavelength.

A key feature of our methodology is the employment of a flat-top intensity distribution in the laser beam. Comparing to the conventional case of the Gaussian intensity distribution, a notable advantage is the consistent size of the damage patterns (craters) in both transverse directions, irrespective of variations in pulse energy or number of pulses impinged. This consistency is not achievable with traditional Gaussian distributions, making this approach more precise and predictable. In addition, the flat-top DUV laser source may be used for the removal of coatings on transparent substrates.

Processing of Transparent Glass Using a Femtosecond Duv Flat-Top Laser Source

The parameter space of beam shaping methods for laser driven processes is getting broader looking at spatial light modulators or coherent beam combining. While systems technology is improving, the knowledge on using beam shaping is mostly empirical driven and not - yet - based on a comprehensive understanding of causalities in the process physics. This presentation will, based on a comprehensive literature study, show some fundamental thoughts on how to connect beam shaping to process physics. To do so, laser deep welding is used as an example process, ready to be improved. In the presentation systems technology will be touched and compared. A process driven view on beam shaping will be developed and then connected to systems technology. Own research results will be used to underline the hypotheses given.

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Generative adversarial network (GAN)-based Prediction of Thermal Residual Stress and Melt Pool Characteristics in Laser Processing of Carbon Steel

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Advancements in Femtosecond Laser Drilling Techniques for Through-Glass Vias