One big challenge in understanding laser ablation processes during microprocessing is to understand influences of surface morphology, which can substantially change the light-matter interaction. For the purpose, we developed an in-situ three-dimensional depth profile measurement system with nanometer precision, which enabled pulse-by-pulse monitoring of changes in surface morphology during multi-shot irradiation. We performed systematic measurements on the changes in depth profile as a function of laser fluence and the number of irradiated pulses with various material, and conclude that laser-induced embrittlement of a target material plays a decisive role.

The use of texturing on functional surfaces in order to speed bone growth and provide other patient benefits is well documented. Texturing can be achieved through various processes including blasting, chemical etching, and laser texturing. Blasting and etching, however, create a random surface and increase both cost and risk by requiring multiple part handling and cleaning operations, as well as use of consumables (e.g., blasting materials, acids) and infrastructure. A functional surface that is produced using laser light and an appropriate shield gas under a digital process results in a repeatable, structured functional surface that is essentially identical

The challenge to create corrosion resistant marks and labeling crosses many industries that require robust traceability methods including medical devices and instruments. The benefits of ultrashort laser marking are demonstrated in a comparison to nanosecond laser marking through observation of formed laser induced periodic surface structures (LIPSS), EDX/XRD, corrosion resistance and long term durability under clinical conditions on medical grade alloys. Traceability through unique device identification (UDI) is realized by combining complimentary technologies to format compliant sequenced data. Thereby, the obstacle of UDI and corrosion resistant marking for medical devices and instruments can be met with such an industrial solution.

We address two important challenges in the field of ultrashort pulse shaping into Bessel beams for nanochannel drilling. First, high quality Bessel beams are essential for controlled energy deposition. Second, the maximal angle used up to here for channel drilling was 26 degrees. Here, we generate high quality Bessel-Gauss beams with a setup based on reflective, off-axis axicons. The cone angles are up to 35 degrees. This corresponds to central spot diameter down to 0.5 µm FWHM. We report femtosecond laser nanochannel drilling down to typically 100 nm over at least 30 µm length in glass.

In the early 2000s, ultra-short pulse (USP) laser technology was mainly used for scientific experiments. By reaching true athermal machining [removing material at exact dimensions with no thermal damage] powerful manufacturing efficiencies were possible. The U.S. Department of Energy issued a grant in 2012 to develop a USP manufacturing process for Gas Direct Inject (GDi) fuel injectors resulting in a process offering superior quality and design flexibility that has helped automakers maximize fuel efficiency and minimize tailpipe emissions. We will discuss the application of USP lasers for drilling micro-holes in GDi fuel injectors, and how USP lasers provide exceptionally precise, fast, and reliable results for industrial micromachining.

Using a nanosecond fibre laser surface texturing of polycrystalline diamond single point cutting tools is proposed to improve diamond wear properties and reduce adhesion of workpiece material in machining aluminium alloys. Topographically different textures were manufactured on polycrystalline diamond cutting tools using a fibre laser milling process, the inserts were tested under dry conditions and benchmarked in turning aluminium alloys to evaluate the lubrication and anti-adhesion properties of the laser manufactured cutting tools. The online monitoring and post-processing of the cutting forces allowed the identification of the tool design which improved the cutting tool lifetime when compared to benchmark inserts.

Ultrafast laser-material processing has been idealized as a one-way interaction — the laser beam modifies the material, the end. The possibility of the changes in the material modifying the laser beam, in return, and that this could open new doors was overlooked. Our approach is to exploit such interactions, which has already led to several striking advances: creation of laser-induced nanostructures with unprecedented uniformity (Ilday et al., Nature Photon., 2013), superefficient ablation (Ilday et al., Nature, 2016), self-organized 3D structuring of silicon (Ilday et al., Nature Photon., 2017), self-assembly of colloidal nanoparticles (Ilday et al., Nature Commun., 2017).

While material processing in DUV region has remained a frontier, we have developed several type of excimer lasers to explore new laser processing. The excimer lasers at 193 nm and 248 nm have been used in the semiconductor manufacturing for long years, and have field-proven highly stability and reliability. The 248 nm excimer laser can be applied to the process of organic materials for semiconductor packages. We confirmed that it is possible to form a via of 5 μm or less in an organic film with a film thickness of 5 μm. We will report the result of processing organic materials with 248 nm excimer laser.

Glass light pipes are fabricated using femtosecond laser irradiation followed by etching and thermal processing for surface roughness reduction. Turning mirrors and combiners, or splitters, are demonstrated. A critical step is assembly of the light pipe for coupling to a source or detector, which requires alignment and adhesives for attachment. A combination of structures has been realized to aid in assembly and optical transmission. Coupling from a distributed source through a lens array and into a light pipe array has been pursued for a waveguiding solar concentrators. The opposite propagation direction enables LED coupling and light distribution.

Ultrashort laser irradiation of metal targets results in a variety of coupled processes, such as energy deposition on surface, electron-ion heating and diffusion, as well as thermal ablation and plasma expansion, mechanical rupture below the surface, and melt flow, modifying the initial surface morphology on micro/nanometric scales. Multidimensional simulations capable to predict the consequences of inhomogeneous absorption on hydrodynamic processes are performed in order to elucidate the mechanisms of surface micro/nanostructure formation and material removal during multipulse laser ablation in regimes below, near and above laser ablation threshold.

In this study, a surface pre-treatment method for applying a metallic coating on a fiber reinforced plastic substrate is presented. Laser structuring with a pulsed laser source is used to create structures on carbon fiber reinforced epoxy. A nickel-chromium coating is applied by atmospheric plasma spraying. A combination of matrix removal and trench structure exceeds industrial requirements. Using pull-off tests, an average adhesive strength of at least 20.3±2.7 MPa was achieved between the coating and the substrate before composite fracture was observed.

We report on femtosecond laser microfabrication (FLM) of a PMMA inertial size-based microfluidic sorter with enhanced throughput. The Lab-on-a-Chip (LoC) device consists of contracting and expanding channels provided with siphoning outlets, for continuous sorting. Differently from soft lithography, which is the most used technique for LoC prototyping, FLM allows developing 3D microfluidic networks on both sides of the chip, making it possible parallelization of the sorting process and consequent increase of particles processed per unit time. We investigated several device layouts (at different flow rates) to define a final configuration maximizing the trapping efficiency and throughput.

The laser welding of transparent substrates is a promising technique for different sectors: optics, microfluidics, healthcare industries… Actually, this technology ensures a non-contact, high-quality, flexible and rapid process. Furthermore, the laser welding process only induces local heat accumulation which is compatible with biological substances. The present study proposes a new technique based on electrostatic forces for performing the welding between transparent/transparent substrates while being independent of the workpiece flatness and keeping a uniform closed contact between substrates. Different laser sources and processes have been investigated with the target to ensure the best hermeticity and optimal joining dimensions according to the dimensions of the channels. A special attention is focused on the use of an ultra-short pulsed laser combined with a specific process strategy for ensuring the joining quality and the compatibility when a tiny welding seam is needed. Finally, the laser solution proposed in this study has been tested on real microfluidic chips putting in evidence the efficiency of the laser welding.

The surface treatment of micro- and nanolayers by means of linear scanning with a line-shaped laser beam gains more and more importance. Beyond optical properties provided by anamorphic beam shaping and homogenization of high-power laser beams, future system concepts will have to consider additional requirements of industrial manufacturing environments. We present a line focus system for debonding of flexible OLED displays (laser lift-off), which focuses on a compact and rugged design. We discuss both, optical and mechanical layout. The optical key parameters are presented and validated by simulation and experiment. We demonstrate the implementation of a functional model.

In this work we present femtosecond laser lift off (LLO) technique for GaN coating separation from sapphire substrates. We demonstrate that using rapid raster scanning technique it is possible to achieve successful delamination of GaN coatings with low surface roughness without any stitching artifacts and at industrial processing rate. Several delamination regimes can be identified in femtosecond LLO: thermal decomposition, stress induced peeling. These results show that femtosecond laser LLO could surpass nanosecond LLO by the achieved quality and overall control of delamination processes.

We will present a new stealth laser dicing system for high precision wafer dicing based on Bessel beams. In our system, a spatial light modulator (SLM) is used to generate a Bessel beam from a femtosecond laser, whose characteristics (e.g., length of focus, aspect ratio and intensity distribution) and location can be controlled directly through the SLM. Mathematical models have been derived to better control the Bessel beam, e.g., minimizing side lobes or optimizing intensity distributions along the optical axis for dicing. Experimental results will be presented to demonstrate the improved dicing results, i.e., improved speed and resolution.

We propose a novel process for low temperature poly-Si (LTPS) thin-film transistors (TFTs) by KrF excimer laser doping with a phosphoric-acid coating. In this method, implantation and dopant activation can be performed at low temperature and low cost. After the laser doping, the mobility, carrier concentration, activation ratio, and resistivity of poly-Si were 61 cm2/Vs, 1.5 × 10^18 cm-3, 18.1 %, and 0.08 Ω⋅cm, respectively. It was confirmed that the low resistivity of poly-Si was achieved by excimer laser doping. In this presentation, we report the IV characteristics of the LTPS TFT fabricated by this method.

Femtosecond laser micromachining is a tool of increasing significance because of high quality and high speed capabilities. In this context, we develop a process for laser ablation of crystalline silicon over a chosen area based on laser milling technique. The process is applied for creating macro-sized cavities in Silicon-on-Insulator (SOI) substrates. The micromachining followed by selective etching of Silicon using XeF2 gives free standing membranes of silicon on buried oxide. RF circuits on such membranes are shown to perform better than specialized RF-SOI substrates. This is of great interest for future wireless applications and also potentially sensor technology.

The welding of glass using ultrashort laser pulse has attracted much attention due to its potential applications in many fields such as solar cells, implanted microelectronics, OLED, MEMS, micro sensors and so on. However the optical contact which requires a distance between two glasses less than 100 nm is a very harsh requirements in practical engineering applications. A welding method of glass, which adopts bursts sequences of ultrashort laser pulses oscillated in a small region to react more glass material and release heat stress gently, is presented in this paper. In this way, a stable and mild liquid pool with more melt glass can be achieved to weld glasses with large gap. The maximum gap distance between two glasses is almost 40 μm which is an order of magnitude higher than other methods, and the joint strength of the glass weld with the natural contact gap of 10 μm is up to 64 MPa. At last, the encapsulation experiment of the welding glass with a closed area was carried out to prove that the sample can guarantee good sealing in 100 hours.

CO2 glass ablation technology provides a very high degree of flexibility in the design of optical fiber sensors and optical probes for medical, sensing and industrial applications. In this paper, we review fabrication techniques for the design and manufacture of such devices, including diffusers, lensed fibers and cladding light strippers. We present an experimental characterization of the optical performance as well as a detailed description of the fabrication process for these devices.

Fabrication of microstructures on needle shaft has been considered to optimize needle treating effect. In this paper, we discuss methods for fabricating micro groove on stainless steel needle shaft using a femtosecond laser. The groove features produced using different processing parameters, such as pulse energies, scanning speed and repetition, will be experimentally investigated. A precision groove will be fabricated with the optimized laser parameters. The surface morphologies and feature size will be presented.

Anti-reflective structures formed by periodic tapers in one dimensional, have been fabricated by femtosecond laser processing. By increasing the scan speed of laser beam, we decreased the effective pulse number continuous irradiated in unit time to reduce the thermal influence, which efficiently avoided the molten materials during processing. Aspect ratio (= depth/pitch in tapers) increased to 2.25 and smooth surface of the taper was obtained. We fabricated tapered structures with different pitches, and evaluated their anti-reflection characteristics experimentally and theoretically at terahertz frequencies (0.1 THz ~ 2 THz). The experimental results showed that the Fresnel reflection is almost decreased to zero at a wider frequency band, and the measured frequency dependence of reflection in the grating structures is good agreement with theoretical ones. These results showed that the laser processing is very useful to fabricate anti-reflection structures with precise dimensions.

Carbide nanoparticles are used in various applications. However, conventional fabrication methods tend to be complicated and several steps are needed until fabrication. In this work, we aimed at developing a relatively simple one-step method of fabricating carbide nanoparticles. We employed femtosecond laser ablation in hexane to fabricated particles. Shape observation by SEM confirmed the formation of nanoparticles (diameter: 20~400 nm). Elemental mapping showed that carbon is uniformly distributed in the nanoparticles. Results of XRD showed that carbide nanoparticles with different plane orientation were fabricated. Chemical bond analysis by XPS was performed to confirm the bind of carbon and target materials. These results suggested that nanoparticles of SiC and MoC could be easily obtained by the femtosecond laser ablation in the hexane.

Recent years have seen an increase in the demand of laser processing of transparent materials because of the numerous applications, such as the formation of through-silicon vias, glass scribing, the creation of optical wave guides, and so on. Furthermore, laser processing is expected to be used for fabricating photonic devices and circuits. Although significant research efforts have focused on laser processing of transparent materials, many unexplained mechanisms remain to be elucidated. In particular, mechanisms that remain unclear include plasma absorption and the process whereby traces expand when using double pulses. In 2017, to improve the laser-processing speed and efficiency, we proposed a method for cutting transparent materials called the “double-pulse explosion drilling method,” which uses two laser pulses of differing wavelengths to create internal modifications in a material. In the present study, we use the double-pulse method to drill through transparent materials and investigate how the second pulse affects laser-beam absorption and the generation of processing traces. We used a picosecond laser with pulses at 532 and 1064 nm for the first and second pulse, respectively. The target material was fused silica glass. The results clarify how the use of double pulses improves the processing efficiency. This presentation gives the experimental results and discusses the processing mechanisms at work in the double-pulse method.

Laser processing of metals can produce superhydrophobicity through induced surface texture and chemistry modifications. This study investigates the transition between highly wetting superhydrophilicity and superhydrophobicity after laser processing. This time-consuming process, inhibitive to industrial value, is reduced through low temperature annealing. Careful examination of the evolution of wetting properties throughout the annealing process is indicative of the nature of the chemical pathway of the transition. Finally, the value of the laser processing technique to produce patternable control of wettability is explored. High contrast wetting regions are fabricated and studied for applications in microfluidic devices and water harvesting devices.

CEA designs, studies and manufactures targets dedicated to laser experiments on the MegaJoule laser facility. These centimetric experimental objects are the place of laser/matter interactions: their designs are continuously evolving and combine many different materials and with various geometries. Their manufacturing requires high versatile and accurate level means. Among these technologies, laser micromachining means have been developed – namely based on excimer or femtosecond lasers. They combine the unique capacity to process many different materials with an outstanding precision and a small affected zone. In this study, we report experimental data related to tantalum oxide aerogel (Ta2O5) samples – low density material of interest for laser/matter experiments. This work aimed to get a first set of operating parameters for deep static drilling. In that goal we used different kind of laser sources: 193 nm excimer laser, Ti:Sa or Ytterbium-based femtosecond lasers. Various parameters have been explored like fluence, wavelength, pulse duration and are related to ablation rates.

We report on the experimental and theoretical study of ultrafast laser induced optical breakdown on the surface of fused silica to elucidate the mechanism of damage formation and sub-optical-cycle dynamics in material processing using single and a burst of two femtosecond laser pulses. Ionization pathways, including photo-ionization (PI) and avalanche ionization (AI), are investigated by using single-beam and double-beam laser damage threshold measurements, which are used to analyze electron dynamics and extract the avalanche coefficient. The relationship between damage size and laser fluence is interpreted as a result of a combination of PI and AI. Electrical field rather than laser intensity is the fundamental influential factor in PI, and AI is found to play a significant role in creating the free electron density needed for optical breakdown. These findings are verified by a double-pulse delay-scan experiment where two cross-polarized pulses are used to induce damage with delay within a few optical cycles. Variation of the damage diameter is observed within one optical cycle, which is explained by the periodic change of polarization in the combined electric field. This finding shows the potential of controlling laser induced damage by tuning the temporal overlap of a burst of ultrashort laser pulses.

In the present study, laser patterning of fused silica using single nanosecond laser pulses (pulse duration 1 – 50 ns, wavelength1064 nm) has been performed by using the LIBDE method. In the particular experimental design used, the absorption process of the laser pulse energy is separated from the etching process of the fused silica by an organic spacer layer. It was found that in dependence on the laser and the material parameter used, either a smooth surface pattern can be achieved or the laser processed area is covered with laser-induced periodic surface structures (LIPSS).

The transient optical properties and ablation dynamics of three metals (Copper, Aluminium and Stainless Steel) after single pulse femtosecond laser irradiation (Copper, Aluminium and Stainless Steel) are examined using ultrafast pump-probe ellipsometry and pump-probe microscopy. The results show the rapid change in the optical properties in the first few picoseconds after the pulse impact, indicating an initial rapid density decrease in the metal skin depth. This is followed by phase change and early stage material motion from 100 ps onwards. Depending on the metal, ablation mechanisms such as spallation and phase explosion can be characterised.

Femtosecond laser surface processing (FLSP) to form self-organized multi-scale structures on aluminum in air, nitrogen gas, and forming gas is presented. During FLSP in air, a thick layer of aluminum oxide forms due to the high reactivity of metallic surfaces immediately after laser processing. Aluminum nitride incorporation into FLSP surfaces can act as a passivation layer to decrease the oxygen content and increase the surface’s thermal conductivity. The FLSP structures are characterized using x-ray photoelectron spectroscopy (XPS), energy dispersive x-ray spectroscopy (EDX) and cross-sectional analysis.

In this work, we report on the fabrication of laser induced periodic surface structures (LIPSS) on stainless steel, using bursts of 200 fs sub-pulses at a wavelength of 1030 nm. A cascade of birefringent crystals was used to generate the bursts with tunable number of sub-pulses and intra-burst delays varying between 1.5 ps and 24 ps. Being such a delay shorter than the typical electron-lattice relaxation time in metals, the sub-pulses impinge on the sample surface when the material is still in a transient state after excitation from the first sub-pulse, thus allowing peculiar structures to be generated depending on the burst features. We obtained 1-D and 2-D periodic surface structures and investigated the influence of number of sub-pulses and polarization on their morphology. In particular, when bursts composed by all-aligned linearly polarized sub-pulses were used, 1-D LIPSS were obtained with different periodicity and depths depending on the number of sub-pulses. Bursts with crossed linear polarization or circular polarization sub-pulses produced 2-D LIPSS with morphology varying from triangular structures arranged in hexagonal lattice to pillar-like ordered or disordered structures depending on the bursts features. In most cases these structures exhibit a superhydrophobic behavior, as assessed by static contact angle measurements, which is achieved after a time of exposition to laboratory air. By XPS analysis we investigated the chemical variations occurring on the surfaces over this time.

Biomedical implants are a part of those new objects requiring very high level of accuracy on complex geometries: cylindrical or hemispherical shapes. LASEA has developed a system combining femtosecond laser with 7 simultaneously moving axes: 5 mechanical axes and 2 galvanometric axes. The laser parameters and strategies are controlled owing to laser specific developed functionalities. Another challenge to overcome is the research of laser parameters which is time and material consuming. In order to make this research more efficient, LASEA has developed a tool named LS-Plume which simulates the profiles for different sets of parameters. In this work, we focus mainly onto biomedical implants, such as stent cutting and hip implants texturing. Fast texturing of 3D part is demonstrated and evaluated.

Comparison of dual-pulse versus single-pulse femtosecond laser surface processing (FLSP) techniques for producing self-organized micro/nanostructures on copper is presented. Using single-pulse FLSP, self-organized microstructure formation on copper requires higher fluence than most metals, which results in non-uniform processing, low processing efficiency, and limitations on the control of the structures produced. We demonstrate that dual-pulse FLSP techniques can be used to produce microstructures on copper more efficiently than using single pulses, with better control of the surface structures produced. Cross-sectional subsurface microstructure analysis results are also presented for single-pulse versus dual-pulse FLSP functionalized copper surfaces.

Surfaces with well-defined features (e.g. periodic structures) have shown to exhibit outstanding properties. The design of these textured surfaces often follows a biomimetic approach motivated by living organisms which developed over time through natural selection and evolution. The efficient production of these versatile patterns still represents one of the greatest technical challenges today in the development of new customized surface functionalities. Direct Laser Interference Patterning (DLIP) has been identified as an outstanding technology for the efficient fabrication of tailored surface structures. This method can show impressive processing speeds (up to 1 m²/min) as well as a superior flexibility in producing extremely versatile surface structures. This work gives an overview about recent developments of the DLIP technology by focusing on the topics: structure flexibility, process productivity, technical implementations and recent examples of achieved surface functionalities.

Laser-induced self-organized processes like IPSM-LIFE (laser-induced front side etching using in-situ pre-structured metal layer) allows large-area sub-µm- and nanostructuring of thin metal layers and dielectric surfaces. At the IPSM-LIFE, a first irradiation step result in the structuring of the metal layer and a second irradiation result in the removal of the metal and in a structuring of the dielectric surface. The metal layer modifications allow a macroscopic adjustment of the optical properties as well as of the water contact angle. The localized modification of the optical properties allows the fabrication of high-resolution greyscale images. Furthermore, the pre-structured metal layer can be used as a mask for a reactive ion beam etching of the dielectric with high aspect ratio. The resultant surface topography was analyzed by optical, atomic force and scanning electron microscopy.

Laser-induced Periodic Surface Structures (LIPSS) are typically manufactured using a focused laser beam. A method to raise the production rate of LIPSS could be increasing the spot size of the laser beam. The latter can be achieved by processing the surface with a defocused laser beam. The purpose of this study is to verify that the LIPSS properties (periodicity and amplitude) of in focus and defocused processing do not differ. Therefore, Low spatial frequency LIPSS (LSFL) have been created on single crystal silicon with picosecond laser pulses with a wavelength of 1030nm with varying laser spot diameters obtained by a defocused laser beam. The laser processing parameters have been adjusted theoretically and experimentally to obtain similar LSFL for all studied laser spot diameters. The periodicity and amplitude of the LSFL were measured by SEM and AFM analysis. It has been found that the periodicities and amplitudes of the LSFL do not differ within the measured stochastically spread, when LSFL were created with larger laser spot diameters than the focal diameter.

In this study, a unique DLIP-workstation is introduced, consisting of a ps-laser, several DLIP optics and a special positioning system for cylindrical parts. The system allows the patterning of cylindrical parts up to 600 mm in length and 300 mm in diameter. The structures, consisting of line-like or dot-like patterns with periods ranging from 5.5 µm down to 1.0 µm, can be produced with record processing speeds up to 5700 mm²/min. Finally, the implementation of these structured sleeves in a roll-to-roll system is demonstrated for imprinting polymer foils at an impressive surface throughputs of 12.5 m²/min, corresponding to web-speeds of 50 m/min. Additionally, some examples of the decorative elements processed by these technique are presented.

This study reports on the application of the Direct Laser Interference Patterning method for the fabrication of holographic motives. The advantages of this method over conventional laser processing methods in terms of resolution, flexibility and throughput are analyzed. It is showed that interference approach for formation of diffraction gratings provides faster fabrication speed together with enhanced visual effect of the structural colors. The control of the period of the formed patterns provided the ability to form exact structural colors, which preserved the visibility of the motives across the whole structured area at certain observation conditions. The capability to improve further the fabrication speed, required for several industrial applications, is demonstrated using a Roll-to-Roll hot embossing system, permitting to replicate holographic motives formed by DLIP on PET foils. Finally, the first tests of inline monitoring method are presented, which is proposed for controlling the quality of the imprinted structures.

Laser-induced modification of local refractive index was studied in thin films produced form multi-component glass ceramics. GAP-Se films with different thicknesses ranging from 1 to 25 µm were irradiated with focused nanosecond-pulsed laser light at the wavelength 2 µm. Following a series of heat treatments, the resulting material properties were extensively studied to reveal the resulting depth-dependent composition, film morphology and optical properties. A maximum positive refractive index change of 0.07 was demonstrated which varies with film thickness and exposure dose while maintaining required optical quality.

Laser ablation, a basis for the laser micromachining, is of great interest for various energy and device applications. Improvement of laser-matter coupling is critically important to enhance the laser ablation hence to improve the laser micromachining. To address this need, we apply a uniform axial magnetic field (0.05-0.4 T) and report a strong enhancement of a 20 nanosecond UV (355 nm) pulse laser ablation of silicon and several metals by a factor varying from 1.3 to 69. Analysis of the basic ablation mechanisms suggests that the major contributions are from magneto-absorption, magneto-thermal effects, and nonlinear propagation through magnetized ablation plasma.

Materials processing using femtosecond laser pulses offers the potential for high-precision manufacturing. However, due to the associated nonlinear processes, even small levels of experimental noise (e.g. instability in laser power, or unexpected debris) can result in substantial deviations from the desired machined structures. Hence, there is much interest in the development of closed-loop feedback processes. Here, we will present the first demonstration of the application of a convolutional neural network for identifying the experimental parameters exclusively from camera images of the sample during machining, and leading the way towards real-time corrective ability for laser machining.

Interest on Laser Induced Periodic Surface Structures are continuously growing due to their potential applications and the increasing diffusion of ultrafast laser systems. Despite decades of researches and proposals, a complete and definitive model able to predict all the phenomena was not yet been found. In this work some considerations about the definition, formation and stability of regularity in LIPSS in dependence of laser parameters and processed materials will be presented and discussed.

Electrospun polylactide (PLA) nanofiber nonwovens are promising candidates for applications in tissue engineering. They may combine the advantageous chemical properties of PLA with a highly porous three-dimensional structure, which promotes the transportation of nutrients and the cell proliferation into the scaffolds. In this work, we tested different laser micro material processing strategies to optimise the surface topography of the PLA nanofiber nonwovens for cell attachment. It was found, that the wetting behaviour of the nonwoven samples could be switched between a hydrophobic and a hydrophilic behaviour by balancing laser induced thermal processes and gentle laser ablation.

Two kinds of interdigitated microelectrodes were prepared by laser direct writing using graphene oxide (GO) and TiO2 nanoparticle　stowards sensor applications. One is a TiO2 nanoparticle-deposited rGO/GO/rGO structure which was prepared by laser direct writing on a GO-coated PET film and a TiO2 sol solution deposition. Another is a TiO2/rGO hybrid interdigitated microelectrode prepared by laser direct writing on a TiO2 nanoparticle-GO hybrid film. The UV light sensitivity of the TiO2 nanoparticle-deposited rGO/GO/rGO interdigitated microelectrode and the oxygen quenching behavior were applied to oxygen sensing. The TiO2/rGO hybrid interdigitated microelectrode showed the response to visible light.

The realization of micro-disk resonators (MDRs) of high quality (Q) factors using lithium niobate on insulator (LNOI) as the substrate has spurred great interest in developing on-chip nanophotonic structures. Here we report on fabrication of crystalline lithium niobate microresonators with quality factors above 10^7 as measured around 770 nm wavelength. Our technique relies on femtosecond laser micromachining for patterning a mask coated on LNOI into a microdisk, followed by a chemo-mechanical polishing process for transferring the pattern to the LNOI. Nonlinear processes including second harmonic generation and Raman scattering have been demonstrated.

Gaussian intensity profiles are widely used in the field of laser material processing. Nevertheless, there are applications, where the inhomogeneous beam profile is not acceptable. We show that refractive beam shaping systems provide very good results for generating tailored focal intensity distributions, e.g. top-hat or doughnut shaped profiles. Even though using just one beam shaping system the width of the profiles is scalable. Beyond, the device is suitable for working with a scanner and F-Theta lens as commonly used for material processing. Results of material processing of fused silica and steel are compared for different focal intensity distributions.

In this study, an optical setup based on two phase-only spatial light modulators is presented, capable to shape two parallel laser beams. Each of the light modulators creates different and complementary Gaussian multi-spot distributions in the focal plane. By the polarization based combination of two differently shaped beams, a multi-spot beam profile with higher multi-spot density than for a single spatial light modulator setup can be obtained without speckles to appear. Beam shaping results are characterized by means of a beam profile camera and compared to a single spatial light modulator setup. Beam shapes generated by the presented setup are applied to ultrashort pulse laser ablation of metals. The potential of the presented optics is discussed regarding ground roughness and waviness of the ablated structure.

Transparent materials processing by ultrashort laser pulses facilitate a plurality of industrial applications. Pump-probe diagnostics is a powerful tool for analyzing the laser matter interaction for process development. In order to make this tool accessible under parameters more realistic for advanced applications, the capabilities are expanded by options for spatial and temporal pulse shaping, burst options and high repetition rate of the pump. Combined with probe of infinite delay, incorporation of polarization microscopy and high speed camera for operation under beam dynamics, different effects on multiple temporal and spatial scales can be observed. We present results melt generation and modification cutting.

For high quality thin film laser patterning the removal process must prevent edge delamination, substrate damage and residual debris re-deposition. Spallation is a photomechanical process that provides an efficient thin film removal under confinement conditions in single pulse regime. But when the process involves dynamically overlapping multiple laser pulses (i.e. to form continuous lines), single pulse spallation strictly no longer applies. The aim of this work is to improve our empirical understanding on how laser pulse overlap affects the spallation process when ultrafast thin film patterning is performed close to the film ablation threshold by varying pulse duration, material and intensity profile.

We present a method based on simultaneous spatiotemporal focusing (SSTF) of the femtosecond laser pulses that enables to fabricate 3D structures on the centimeter scale. The isotropic spatial resolutions of fabrication have been achieved in different materials, making this approach easy to implement. In addition, based on the SSTF scheme, we demonstrate 3D microprocessing in glass with a nearly invariant spatial resolution for a large range of penetration depth without any aberration correction.

Fibre Bragg gratings display a periodic modulation of the refractive index inside the core of an optical fibre providing a strong reflection for target wavelengths. Manufacturing via femtosecond laser writing creates permanent modifications that can be easily tailored and withstand high temperatures. For the point by point inscription method, aberrations can limit the potential for fabrication using air lenses, such that the fibre is often immersed in oil to reduce refraction at the fibre interface. In this work, we present two different strategies for beam shaping using adaptive optics to write structures directly inside fibre with air based objective lenses.

Material removal-based surface cutting, drilling, peeling, as well as material destructure-based internal dicing have been fully integrated into processing module & system for industrial-scale fabrication of mobile devices. Our results provide a guidance in engineering most suitable laser solutions for achieving quality, throughput and cost expectation. 1. Fully understand the mechanism and technical details of laser material interaction and develop reliable process according to material properties of glass, sapphire, ceramic, FPC and PCB. 2. Our engineering solution is to integrate laser, material process and optical module in a complete processing system. Different from only investigating laser processing, it combines all factors of laser, optics, processing, motion control to provide a finalized and optimized result. Although we work on engineering solution, the key impact factor is still processing parameters, including pulse energy, repetition rate, focal spot size and beam shaping.

The use of 100 W class, USP lasers to increase the throughput of several fabrication processes is accompanied by detrimental heat accumulation phenomena. Novel beam engineering strategies are required to guarantee high throughput with high machining quality. Here we show that increasing from 10 to 100 W, the power of a femtosecond laser jointly with fast scanning systems (both polygon scanner head and 2D, fast, galvo-head) and multi-beam optics (both a DOE and an SLM head) enables significant throughput improvement for several laser processing (×10 in micro-cutting, even higher in surface texturing and matrix micro-drilling) while keeping good machining quality.

High production costs, restricted process reliability, small energy- and power-density, as well as relatively short operational lifetime are the main issues of lithium-ion batteries (LIBs). LIBs with high-energy and high-power density can be realized by introducing a three-dimensional (3D) battery concept, which offers an improved electrolyte transfer in thick film electrodes and an improved lithium-ion transport kinetic. For developing next generation batteries including the 3D battery concept for large footprint areas, high energy materials such as nickel-enriched Lithium-Nickel-Manganese-Cobalt-Oxide (NMC) for cathodes and silicon-based anodes are introduced. The main drawbacks of these types of active materials regarding commercialization are their rather small lifetime due to enhanced mechanical degradation and their restricted chemical stability during electrochemical cycling. Ultrafast laser processing for establishing an advanced electrode design is flanked by an advanced material design, i.e., thin film passivation of active material for maintaining structural and chemical stability on particle level. Such thin film passivation is realized for anodes and cathodes by carbon- or alumina-coated silicon nanoparticles and LPO(Lithium-Phosphate)-coated NMC, respectively. Cyclic voltammetry is proving the successful combination of laser generated 3D electrode architecture and material concept while galvanostatic measurements reveal that batteries with structured electrodes provide an enhanced capacity retention and an improved lithium-ion diffusion kinetics compared to cells with unstructured electrodes.

Lithium-ion batteries aim towards increased energy density at high active mass loading per unit area and low porosity. The challenge is a low rate capability due to restricted mobility of lithium-ions. Selective laser ablation of the binder opens the pores. However, the active material exhibits heat affected and molten zones. Cathodes with variable densities are electrochemically analyzed. Highly densified cathodes with a porosity lower than 28% exhibit a distinct improvement of rate capability at C-rates greater than 2 C. At high current rate of 5 C more than 20% in relation to cathodes without laser treatment was achieved.

TPP-compatible, homogenous composite resins with high nano-filler concentrations have been developed using MWNT and AgNWs. Various functional 3D micro/nanostructures have been successfully developed via TPP-lithography. The MWNT-polymer composite exhibits multifunctional reinforced properties, including enhanced mechanical and electrical properties with high optical transparency. The AgNW-polymer composite and the femtosecond laser nanojoining of AgNW junctions demonstrates a further enhanced electrical conductivity. Moreover, a strong temperature dependence of the conductivity of the AgNW-polymer composite was observed and analyzed. The 3D printing, nanomaterial assembly and joining method demonstrated here represent a new opportunity for developing functional devices for a broad range of applications.

Laser aided additive manufacturing using ultrashort pulses at a wavelength of 1030 nm and 515 nm is presented. The layer wise build-up is based on the powder bed method. The process is governed by extremely fast melting and re-solidification processes yielding melting pools confined to the focal area. Consequently, highly resolved elements with wall thicknesses of a few 10 µm can be achieved. Ultrafast laser matter interaction allows the use of new materials with extreme properties such as high melting point, low absorptivity or high thermal conductivity. In particular, the processing of copper, glass and oversaturated alloys can be demonstrated.

The combination of ultrashort pulse lasers with Bessel-like beam profiles offers the possibility to cut thick glasses (several mm) in a single pass process, in principal suitable for industrial purposes. However, advanced beam profiles significantly improve the surface quality of the cutting edge and separability due to a preferential crack orientation. We apply pump-probe diagnostics combined with transmission and polarization microscopy techniques to analyze the laser-matter-interaction of single and multiple laser pulses. Camera recording rates in the 100 kHz range allow continuous investigation of transient effects in stress formation with relevance for crack generation and crack suppression.

Laser-Induced Periodic Surface Structures (LIPSS) present a wide range of well-known properties and applications, while birefringence has been studied only very recently. This new feature enables metallic surfaces with LIPSS show different polarization states for incident and reflected laser beams, making them useful as reflective polarization gratings, with applications in polarimeters, displays, beam splitters, or multiplexers. Additionally, simulations show that depositing a thin film introduces relevant variations in the polarization change compared to the behaviour of uncoated LIPSS, which can help improve their performance by modifying the original properties of the structure and make the fabrication process more flexible.