We propose a hybrid laser microfabrication approach for the manufacture of UV photochemical fused silica microchannel reactors using ultrafast laser-assisted etching combined with carbon dioxide laser irradiation. The manufactured glass microchannel reactors not only enable high transmission rates of multi-wavelength UV light irradiation but also allow micro-flow high-pressure and high-temperature intensification. As a proof-of-concept of this approach, one-step continuous-flow synthesis of vitamin D3 in the manufactured reactors is demonstrated.

Ultra-short pulse lasers have become indispensable in industrial and scientific micro-processing applications, offering advantages like surface texturing, treatment, drilling, and micro-welding. However, these applications also present unique challenges, including process speed, precision, and seamless integration into industries. This paper explores how beam shaping addresses these challenges in micro-processing. Various beam shapes, such as beam splitting, non-diffractive beams, top-hat shaping, U-shaped beams, and triangular beams, are discussed for improving process speed, precision, and integration of ultra-short pulse lasers. The paper also addresses the challenges of fibering the laser for industrial integration and how beam shaping overcomes these hurdles. In conclusion, beam shaping proves to be a valuable tool for tackling the unique challenges of micro-processing with ultra-short pulse lasers, enhancing process speed, precision, and integration into various applications.

A method is demonstrated for large-scale micro-through-hole (MTH) array fabrication in glass substrates for an advanced digital nucleic acid amplification technique (NAAT). The fabricated chip is advantageous to current partitioning devices in terms of speed, cost, and simplicity. To satisfy the requirement of MTH quantities for valid nucleic acid statistics, we improve the laser processing speed by focusing ultrafast Bessel pulses into a glass substrate under continuous translation. A single Bessel pulse can result a single MTH, and hundreds to thousands of MTHs can be produced per second. Preliminary digital NAAT experiment shows promising results of reagent partitioning of the fabricated chip. This work offers a highly efficient and low-cost scheme for glass-based reagent partitioning that will contribute to the wide accessibility of advanced digital NAATs.

The GHz burst mode femtosecond (fs) laser pulses have attracted considerable attention because they can perform better quality and higher efficiency ablation compared to the conventional irradiation scheme of fs pulses (single-pulse mode). Recently, we have demonstrated that the GHz burst mode fs laser pulses can create two-dimensional (2D) periodic surface structures (LIPSS) on Si surfaces. In this paper, we extend the GHz burst mode fs laser processing to form LIPSS on Ti plates. Our aim was to further investigate the more detailed mechanism and explore practical applications. Although the material characteristics of Ti are significantly different from Si, the GHz burst mode fs laser pulses can also create 2D-LIPSS. Then, mesenchymal stem cells cultured on the formed 2D-LIPSS were found to exhibit different behavior on 1D-LIPSS as compared with bare Ti surfaces.

The quest for surface functionalization has driven the development of methods to create nanometer-scale features on surfaces. Conventional laser methods for surface patterning are limited in terms of resolution and pattern control. Here we demonstrate a method that takes advantage of the stable diffraction of light that occurs when a laser beam scans a solid surface immersed in a liquid. The cavitation bubbles formed during irradiation serve as spherical diffraction objects. They are precisely manipulated with thermo-optical tweezers that take advantage of thermocapillary forces generated by the temperature gradient in the surrounding liquid near the irradiation point. In contrast to much of the literature, where laser-induced bubbles are often considered an undesirable side effect, we demonstrate the utility of cavitation bubbles as an advantage for laser patterning in liquid environments. The high viscosity of the liquid, leading to laminar flow conditions, provides sufficient stability of cavitation bubble dynamics for the generation of regular arc-shaped concentric microgroove channels with a depth of several hundred nanometers and a radius of curvature in the micrometer range.

Room temperature liquid metal, such as eutectic gallium-indium (EGaIn) or Galinstan, is a promising conducting material for stretchable electronics due to its unique liquid-inherited properties. However, the fluidic characteristic bounds liquid metal to a substrate since it cannot stand alone without the support of a substrate underneath. This fact limits various applications of liquid metal when it comes to be used in stretchable electronics. Here, we have exposed a continuous wave laser (532 nm) to a liquid metal-silver nanowire film to overcome this limitation and make it become substrate-free. With the substrate-free patterned film, we have demonstrated diverse applications that has not been possible.

TRUMPF Laser & Systemtechnik GmbH is a company offering a wide product portfolio of laser sources, addressing solutions for many industries such as mobility, aerospace, consumer electronics, energy, and data storage. Pulsed short-ns-, ps- and fs- laser sources are interesting for material surface engineering. Surface modification has seen many applications in the recent past, especially for applications such as cleaning or surface preparation prior to welding, gluing, or bonding. In addition, laser surface texturing can create hydrophile or hydrophobic surfaces. However, heat and radiation management of components, in particular where cooling by heat exchange is not possible or less effective, using advanced surface texturing has yet to be explored. For example, vacuum grade microelectronics components might benefit from radiative passive cooling in space environment. In this paper we present results using a ns-laser laser source for surface structuring of metals to enhance attenuation of light and thermal emissivity conductivity. Measurements of emissivity, attenuation will be presented and compared to commercially available surface treatments.

Understanding spontaneous pattern emergence on laser-irradiated materials is a long-standing interest. Periodic surface structures arise from multiphysical coupling: electromagnetics, nonlinear optics, plasmonics, fluid dynamics, or thermochemical reactions. Multi-shot irradiation with ultrafast laser pulses generates stable periodic patterns arising from localized perturbations influenced by disturbances and nonlinear saturation. Describing pattern growth requires nonlinear dynamics beyond classic equations. The challenge is developing an efficient model with symmetry breaking, scale invariance, stochasticity, and nonlinear properties to reproduce dissipative structures. Stochastic Swift-Hohenberg modeling replicates hydrodynamic fluctuations near the convective instability threshold, inherent in laser-induced self-organized nanopatterns. We will demonstrate that a deep convolutional networks can learn pattern complexity, connecting model coefficients to experimental parameters for designing specific patterns. The model predicts patterns accurately, even with limited non-time series data. It identifies laser parameter regions and could predict novel patterns independently.

Ultrafast laser-matter interaction involves multiple physical phenomena at different time scales. Consequently, process development for ultrafast laser processing is also a lengthy, empirical process. Different scientific models provide valuable insights on the underlying physics but are often too complex for practical use. More recently, machine learning has proven to be very effective in predicting and optimizing micro-processing results. However, to take full advantage of these algorithms, an important number of data points are needed for training purposes. Acquiring such a dataset usually requires a significant amount of time, partially negating the benefit of machine learning. The purpose of this work is to study the efficiency of machine learning algorithms to predict the results of a femtosecond laser engraving process, using only a small training dataset describing the engraving depth for different materials, process parameters and laser specifications. We compare the results with an engineering model based on the well-known two-temperature model, present strategies to mitigate the dataset size and compare the results with independent experimental results.

In this work, we demonstrate the application of laser induced forward transfer of metal nanoparticle inks and pastes for the additive manufacturing of linear Ag micro-electrodes on top of thermally sensitive and even multi-stack layers involving challenging surface topographies. The versatility of LIFT has been validated in three use cases: i) the fabrication of gate electrodes for flexible organic thin film transistors (OTFTs); ii) the development of metal grids in flexible organic photovoltaics (OPVs); iii) The combination of LIFT of lead-free solder paste and laser soldering for the digital assembly of optoelectronic integrated circuits (OEICs).

Multi-core optical fibers are widely used for information transfer and endoscopy. However, dispersion effects result in phase noise of the transmitted light fields, limiting applications. This can be characterized holographically. We investigate the use of laser ablation to apply holograms for correcting the phase noise. We show that the desired phase correction can be applied via intensity modulation. We compare the phase shift of single-shot vs multi-shot ablation. Additionally, the ablation is compared to additive manufacturing and digital optical phase conjugation. The presented results demonstrate, that phase corrected light field transfer is possible via optical fibers.

The study compares two laser beam intensity distributions, namely the Gaussian beam and the flat-top, for micromachining applications at a UV wavelength of 257 nm (4th). A novel laser system with integrated beam shaping capabilities, including a flat-top intensity profile is introduced. The differences when micromachining materials using the top-hat intensity profile are compared to the conventional Gaussian intensity distribution.

Femtosecond lasers has the ability to cleanly cut a wide variety of materials with minimal effect to the surrounding material. Also, the availability of high-power industrial femtosecond lasers made it possible to achieve high throughputs, which is critical for high volume manufacturing. In this work, we investigate the benefits of using high-power IR femtosecond lasers in processing: separator foil and anode/cathode material used in Li-ion battery manufacturing, polycrystalline diamond (PCD), polypropylene (PP), high density polyethylene (HDPE) and silicon carbide (SiC). Our studies demonstrate that using a high-power IR femtosecond laser for processing these materials results in high throughputs with acceptable HAZ (heat-affected zone) meeting the demands of the industry.

The aim of this work is to demonstrate the processing of large metal foils by femtosecond laser in a roll-to-roll configuration using 2D Direct Laser Interference Patterning generate by MPLC technology, as an advanced surface functionalization for high-throughput manufacturing. Highly uniform 2D morphologies have been created on stainless steel, with a spatial periodicity of 14µm and an aspect ratio up to 0.7, suitable for numerous applications such as de-icing.

We demonstrated laser-induced broadband emitters (LIBEs) with spectral emissivity higher than 0.96 from 0.3 um to 15 um wavelength to increase thermal radiative energy transport. Localized material removal induced by ultrafast femtosecond laser irradiation results in the hierarchical formation of microstructures decorated with micro-/nano- particles, leading to an exceptional enhancement in a spectral absorptivity on different types of substrates. Finite-difference time-domain simulations validated the effects of surface topology on the experimentally measured absorptivity. Moreover, LIBEs maintain their enhanced spectral absorptivity of 0.92 after heating at elevated temperatures for over 100 hours. Our results provide new insights into the use of ultrafast laser-matter interactions in cutting-edge energy harvesting and thermal management applications.

The accelerated adoption of e-mobility is causing rapid and large-scale changes in power electronics manufacturing. The circuitry for the advanced electronic drive systems must tolerate high voltages, high currents, and decreasing switching times. All of this requires a migration from silicon-substrate based devices to those built on silicon carbide (SiC) crystal substrates. In this work, we present ablation study results using high power ultrashort pulse (USP) lasers for processing crystalline 4H-type crystalline SiC wafers. Ablation thresholds and material removal efficiencies are characterized, and the advantages of using tailored burst output for machining high-quality features is demonstrated.

We irradiate the surface of pure fused silica with few-cycle pulses (duration < 10 fs, central wavelength at 800 nm, repetition of 400 kHz and a pulse energy of ca. 1 µJ) focused at a quasi grating incidence and observe a permanent densification in the irradiated region. A translation of the sample in the direction of the laser results in the direct writing of surface waveguides. The eigen modes of such structures exhibit a pronounced sensitivity to the refractive index of the immediate environment which we exploit to demonstrate direct refractive index sensing as well as plasmonic sensing.

In this work, we study the fs-laser incubation and damage threshold fluence in L-threonine crystals at 515 nm and 1030 nm. The difference observed in threshold fluence, for each wavelength, is associated with the number of photons involved in the multi-photon ionization. The results obtained in this work provide the necessary data for processing L-threonine crystals to achieve photonic devices.

In burst mode, a single pulse is replaced by a packet of multiple pulses of the same energy. Recently, various research groups have conducted numerous experiments on the processing of metals using the GHz burst mode, while the less expensive and more accessible MHz burst mode has been little explored. Therefore, in this study, we investigate the extent to which it is possible to achieve the advantages of GHz burst laser machining by using MHz burst laser (wavelength 1030 nm, intra-burst repetition rate of 40 MHz, repetition rate of 333 kHz, and pulse duration between 300 fs - 10 ps) on metals. We measure the ablation efficiency as the volume removed per energy (dV/dE) when drilling stainless steel foils with different thicknesses (25 μm, 50 μm and 75 μm). The ablation efficiencies are compared for different ultrashort pulse durations (300 fs - 10 ps), for ns pulses, and for a different number of pulses within the burst (at constant burst energy). The results show that a MHz burst mode can be a cost-effective alternative to the GHz burst mode for a broader implementation of burst-mode laser processing in various industrial applications.

Diamond is a wide-bandgap semiconductor known for its distinguished properties. It also hosts many defects, such as the Nitrogen-Vacancy (NV) center. Since one can generate such defects through fs-laser micromachining, an investigation was made to determine the optimal experimental conditions for such feat, where a Yb:KGW fs-laser system operating at 1030 nm, producing 216 up to 1000 fs pulses at 197.5 KHz was used. Microstructures were produced by varying pulse duration and excitation fluence. Through confocal microscopy image analysis, it was determined that NV center generation is proportional to the excitation fluence and inversely proportional to the pulse duration.