This PDF file contains the front matter associated with SPIE Proceedings Volume 11268 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Recent advances in three-dimensional (3D) printing of pure proteinaceous microstructures by femtosecond laser direct write (fs-LDW) are presented. Fs-LDW utilizes light-matter interaction to fabricate micro- and nanostructures along the designated path of the focused laser light. Extremely short pulses suppress heat effects while enhancing the likelihood of non-linear light absorption processes. Fs-LDW thereby allows the fabrication with spatially well-confined features and nearly arbitrary shapes in 3D with a high resolution for diverse materials including protein. Mixtures of protein and photoactivator were usually used so far as precursors to fabricate proteinaceous 3D microstructures. Here, we show that proteinaceous 3D microstructure can be fabricated using the precursor without photoactivator. Such omission of photoactivator might be relevant for biomedical and microfluidic applications because the use of photoactivator is accompanied with the undesired side-effects of photoactivator molecules leaching from created structures and cause physical alteration in the device or allergic reactions for medical use. Raman spectroscopy reveals the absence of photoactivator in the created structures and acid-catalyzed hydrolysis verifies covalent cross-linking as the printing mechanism. We further demonstrate our recent findings in terms of function retention by antibody staining. Due to the diverse abundance of proteins with different native protein functions, we believe fs-LDW of pure proteinaceous microstructures offers many applications in biological studies and medical applications.

Closed micro-physiological systems (MPS) are miniaturized, chip-sized platforms that can be used as cellularized organoid systems to study cellular processes like migration, regeneration or proliferation in vitro. Due to the limited accessibility of the cells inside of closed MPS, the establishment of a well-defined mechanism to induce specific cell damage is difficult. Here we present a novel laser based method to induce well-defined lesions in closed cell layers. This could be a novel tool to study cellular mechanisms of different cell types after injury. The present project aimed to establish well-defined lesion in cellular layers without removing the dead cells and the molecular signaling that is caused by apoptosis. Considering that, we constructed a MPS that was produced by layer laminate manufacturing. According to the experimental needs, the MPS contains two fluidic circuits which include reservoirs, channels, and an integrated micro pump. To establish the method, blood endothelial outgrowth cells (BOEC) were seeded into the MPS previously coated with collagen (5μg/cm²) at a density of approximately 7,5×10⁴ cells/cm². After 3 hours of attachment, a pulsatile flow was applied to the channels. When the whole channel was covered with a BOEC monolayer, laser ablation took place between day 3 and 6 after seeding. To induce the selective cell injury we used a JenLas D2.mini laser that was optically integrated into an inverted microscope. The irradiation took several seconds with a wavelength of 532 nm. The damage and the following regeneration processes were observed by fluorescence microscopy using LIVE/DEAD Viability/Cytotoxicity Kit and Time Lapse recording

We have experimentally shown that selective modification of the PMMA surface with a femtosecond laser irradiation could control the adhesion of cells to the PMMA surface. Using a femtosecond laser, periodic nanostructures were formed indirectly on a part of the PMMA film surface. By performing a cell cultivation test, the cell adhesion density to the substrate was measured. As a result, the cell adhesion density was 7 times higher in the laser processed area than in the non-processed area. This is considered to be due to the fact that the cell adhesive protein adheres well to the surface processed by the femtosecond laser.

Lab on a Chip devices are compact and portable chips mainly constituted by a network of microfluidic channels. They aim at substituting bulk laboratory instrumentations, with the advantages of increasing the automation and the sensitivity of the analysis, reducing the costs and opening the possibility of performing measurements at the Point of Care. Among different Lab on Chips, optofluidic ones have the advantages of optical investigation, but the integration of optical and microfluidic components in a single substrate is very challenging from a technological point of view. A recent fabrication technique, known as femtosecond laser micromachining (FLM), has proven to be ideal for the realization of these devices, allowing the fabrication of the whole device in a single irradiation step. Here, we will present a platelet counter and a microscope on chip, that fully take advantage from the versatility of FLM. To succeed in these works a fundamental aspect to address is the capability to control the sample positioning in the microfluidic channel. A single particle per time should pass in the detection region to avoid the overlooking of specimen. Moreover, a precise control of the sample orientation and position in the channel cross section is needed for imaging. The 3D capabilities of FLM have been fundamental in the realization of advanced fluidic layouts capable of sample manipulation with no need of any additional external field. We have successfully proven red blood cells and platelets counting, as well as single cells, cellular spheroids and drosophila embryos 3D imaging.

Efficient cooling systems are urgently needed because of increasing power density of electronic devices per one semiconductor chip as high as hundreds of W/cm². Recently, we demonstrated that degassing water leads to generation of a water vapor microbubble and subsequent rapid flow under localized heating. In addition, the bubble was found to oscillate at several hundred kHz. In this study, we investigate the dependence of the size and oscillation frequency of the microbubble on the concentration of incompressible gas dissolved in water by focusing a CW laser on the β-FeSi₂ thin film. We found that lower concentration of incompressible gas dissolved in water leaded to smaller size and higher oscillation frequency of a bubble. Furthermore, bubble whose radius is larger than 7.5 μm showed no oscillation in our system. Our work gives a new understanding about the bubble oscillation mechanism and will develop the technique for a novel cooling system using microfluidics.

Femtosecond laser-induced chemical etching (FLICE) has proved itself a powerful approach when attempting to fabricate three-dimensional (3D) microstructures in glass, whereas maintaining a high spatial resolution in fabricating samples of great heights/thicknesses is challenging due to the diffraction nature of light waves. Here, we demonstrate the fabrication of macro-scale 3D glass objects of large heights up to ~3.8 cm with a well-balanced lateral and longitudinal resolution of ~20 μm using the FLICE. Moreover, a freeform hand printed with embedded blood vessel system has been produced. The remarkable accomplishments are achieved by revealing an unexplored regime in the interaction of ultrafast laser pulses with fused silica, which gives rise to depth-insensitive focusing of the laser pulses and polarization-independent selective etching inside fused silica. We examine the difference in the plasma dynamics between interactions of picosecond and femtosecond laser pulses with fused silica glass.

This paper presents a comparison between ablation results for various modes of laser operation: single pulsing, GHz bursting, and regular bursting. We start with the comparison of ablation thresholds of single ultrafast pulses with pulse widths ranging from 300 fsec to 3 psec. Those are contrasted with regular fsec pulse bursting at 20 ns pulse-to-pulse spacing, as well as GHz bursting with pulse spacing of 1.4 nsec. A variety of GHz milling results are presented and contrasted with single pulsing, as well as with 20nsec bursting, as the number of fsec pulses in a burst is adjusted from 3 pulse per burst, to 9, and 17, and for various scanning speeds. Material removal results are presented for milled transparent hard materials, specifically, fused silica, borosilicate glass, sapphire, and diamond. Aluminum and silicon are also included in this milling test for comparison. To maintain proper correlations, similar experimental conditions are used throughout, such as focused spot diameters, fluence, frequency of operation, and scan speed. The lasers used for this study are internally developed at IMRA for material processing. The data include results for 1045nm, 523nm, frequencies up to 1MHz, and power up to 5W.

We compare conventional bursts with GHz bursts in respect of their applicability for surface treatments such as polishing, hardening or surface alloying. It turns out that GHz bursts are more suitable than conventional bursts, especially with respect of energy efficiency and thus for gentle surface treatments with less thermal load for the bulk material. The temporal delay between the pulses is the key factor for surface melting. It is shown that the application of GHz bursts corrects the surface degradation caused by heat accumulation during ablation. This allows a dual process strategy to increase the ablation rates while maintaining the surface quality.

We introduce a novel sub-diffraction direct laser writing process and discuss its advantages compared to common lithographic methods. The fundamental idea is based on the combination of a Stimulated Emission Depletion (STED) with the effect of an Excited State Absorption (ESA). Analogous to the STED-microscopy, an excited spatial volume below the diffraction limit is created. The modified optical properties of this volume compared to the non-excited surrounding regions are used for the subsequent spatially restricted processing based on an ESA. In combination with a required STED- and ESA-compatibility, a variety of potentially suitable processes for excitation, stimulated emission, and ESA are presented for various materials. Here, direct semiconductors such as ZnO are of particular interest for a STED-process. The second essential requirement, an ESA-based processing, was demonstrated experimentally for the first time at a 200 nm thinn ZnO-layer sputtered on a fused silica substrate. For this purpose, an experimental setup consisting of two ns-lasers, one for excitation and one for the ESA-based processing, as well as a variable time delay, was used.

To examine the ablation dynamics of silver thin films by femtosecond laser, we experimentally investigate the plume evolution and behavior of ejected nanoparticles (NPs) via emission and scattering spectroscopy measurements under background pressures of 760 torr, 5 torr, 5 x 10^-3 torr, to 3 x 10^-5 torr. The emission spectroscopy experiments show that the propagation of the ablated plume is affected by ambient pressure. The higher the pressure, the more the propagation of the plasma is suppressed. Under higher vacuum, the lifetime of plasma is shorter due to diminished collisions with background molecules. The evolution of plasma lasts more than 200 ns under 760 torr while it does not exceed 200 ns under high vacuum (3 x 10^-5 torr). Through the scattering measurements, the average propagation speed of NPs is 200 m/s under 3 x 10^-5 torr, 190 m/s under 5 x 10^-3 torr, 155 m/s under 5 torr, and 120 m/s under 760 torr. The ejected nanoparticles from the periphery of the ablated spot exhibit oblique trajectories because of the exerted recoil pressure at the spot center region that is subject to high incident energy densities.

During the last years processing of transparent materials by ultrashort laser pulses has gained interest. Spatial and temporal pulse shaping has already proven its potential for advances, widening existing and opening new application fields. The paper focuses on supporting the application development by extending pump-probe diagnostics via combining pulse shaping capabilities, dynamical beam positioning, processing at elevated repetition rates, energy modulation and high temporal resolution over an essentially infinite range of delay. Applying these capabilities gives inside into effects resulting from spatial and temporal shaping, on the laser matter interaction of individual and of a multitude of pulses, the latter typically effective on larger scales due to accumulation. The influence of beam shaping and processing parameters on the dynamic development of the interaction zone in multi pulse exposure highlights the potential of such diagnostic tools. Observations relevant for development of transparent materials processing ultrafast lasers by absorption induced inside of the workpiece are presented. Initiation and development of cracks as a major aspect in brittle materials processing can be analyzed in detail. Pump-probe polarization microscopy for transient stress birefringence observation reveals that both, pressure waves and temperature gradients from accumulation, are of major importance in scaling industrial processing. Considering these findings facilitates addressing different application fields, illustrated by examples on ultrafast welding and selective etching by shaped beams.

Ultrashort laser pulses offer enormous potential for precise micro structuring, especially of transparent materials [1-2]. When focusing ultrashort laser pulses into the material, the intensity in the focus volume is sufficient to induce non-linear absorption processes, which lead to structural changes in the material volume [3]. In the following study, the localized structural changes were arranged in order to produce cut surfaces for the extraction of 2.5D bodies with potential applications for example in the production of micro implants. The investigations were carried out in polylactide, a bioresorbable polymer. For this purpose, a femtosecond laser source was used which emits pulses of 200 fs pulse length at a wavelength of 1030 nm. Microscope objectives with focal lengths in the range of 12.5 mm down to 2 mm were used, which resulted in focal radius of 1.2 μm in minimum and hence extremely high intensities of about 10¹⁵W/cm² to excite nonlinear absorption effects. Process-influencing parameters such as pulse energy, pulse distance and frequency were varied to investigate their effect on the quality of the cut-out bodies. The feasibility of the technology could be demonstrated on the basis of simple bodies.

Terahertz (THz) optoelectronics have great potentials in communication, imaging, sensing and security applications. However, the state-of-the-art fabrication processes for THz devices are costly and time-consuming. In this work, we present a novel laser-based metamaterial fabrication (LMF) process for high-throughput fabrication of transparent conducting surfaces on dielectric substrates such as quartz and transparent polymers to achieve tunable THz bandpass filtering characteristics. The LMF process comprises two steps: (1) applying ultrathin-film metal deposition, with a typical thickness of 10 nm, on the dielectric substrate; (2) creating periodic surface pattern with a feature size of ~100 microns on the metal film using nanosecond pulsed laser ablation. Our results demonstrate the LMF-fabricated ultra-thin metal film exhibits newly integrated functionalities: (a) highly conductive with sheet resistance of ~20 Ω/sq; (b) optically transparent with visible transmittance of ~70%; (c) tunable bandpass filtering effect in the THz frequency range; and (d) extraordinary mechanical durability during repeated fatigue bending cycles. The scientific findings from this work will render an economical and scalable manufacturing technique capable of treating large surface area for multi-functional THz metamaterials.

Publisher’s Note: This conference presentation, originally published on 9 March 2020, was withdrawn on 25 March 2020 per author request.

Perovskite solar cells (PSC) are a promising low-cost energy source for niche markets, such as energy harvesting semitransparent windows, and colored or arbitrary shaped solar modules for portable power sources or building facades. Furthermore, the possibility to fabricate flexible solar modules allows the integration of the whole manufacturing process into a roll-to-roll facility with the potential of reducing dramatically the fabrication costs. In the quest for high efficiency flexible PSC, the absorbed sunlight can be maximized employing a light trapping technique, such as using a microstructured substrate capable to scatter or diffract the incoming light into multiple directions elongating the optical path in the absorber. This work presents a new strategy to pattern microstructures on polymers suitable as transparent substrates for flexible PSC with enhanced light trapping. This industrial compatible approach consists only on two processing steps. First, a cylindrical metallic stamp is structured using Direct Laser Interference Patterning (DLIP), and next, the stamp is used in a roll-to-roll hot embossing system to transfer the stamp pattern to polymeric foils. Optimizing the DLIP processing and hot embossing parameters, high-quality imprints were obtained with periodic features with a spatial period of 2.7 μm. PSC were deposited onto these structured substrates showing an increase in the light absorption and efficiency. Spectroscopic characterization using an integrating sphere suggests that the PSC efficiency increase is caused by an elongated optical path inside the perovskite due to scattering and diffraction in the visible spectrum.

Laser micro-machining of amorphous PEEK has been demonstrated with 180 fs/1 kHz NIR (775 nm) and NUV (387 nm) laser pulses. The single pulse ablation threshold was found to be 2.01 ± 0.05 J/cm² and 0.23 ± 0.02 J/cm² at 775 nm and 387 nm respectively. The significant difference in ablation threshold is due to the requirement for 3-photon absorption at 775 nm, where PEEK is transparent while significant linear absorption within the material bandgap occurs at 387 nm, enhancing 2-photon absorption. A high 2-photon absorption coefficient, measured to be β₃₈₇ ~ 38 cm GW^-1 supports this view while at the bandgap edge, 400 nm, β400 ~ 0.7 cm GW^-1. Multi-pulse exposure yields incubation coefficients of S₇₇₅ = 0.72 ± 0.01 and S₃₈₇ = 0.85 ± 0.02 hence incubation is significantly reduced in the NUV. Ablation of PEEK with NUV fs pulses demonstrates much reduced melting and re-deposition, thus precision NUV polymer micromachining is accomplished while laser induced periodic surface structures (LIPSS) with pitch Λ < 0.4 μm are observed at the base of ablated regions. Scanned areas exhibit white light diffraction due to this sub-micron periodic surface modulation. With the aid of a phase only spatial light modulator, multi-beam NUV micro-structuring is achieved, speeding micro-processing while reaching a line width < 4 μm with NA = 0.4 objective.

Femtosecond laser irradiation followed by chemical etching (FLICE), combined with femtosecond-laser waveguide writing, has allowed to demonstrate, in the past years, a variety of compact optofluidic devices in fused silica substrate. Applications are diverse and range from biochemical sensing to single-cell manipulation. On the other hand, femtosecond-laser written circuits with high complexity, and waveguides with very low insertion loss, have been reported in Eagle alumino-borosilicate glass (Corning). Here we show that FLICE can be applied to produce buried microchannels also in EagleXG substrate. Our results will enable quick fabrication of microfluidic devices, directly interfaced with complex and low-loss photonic circuits.

The recent development of sources able to deliver laser pulses with a duration of a few optical cycles has created many opportunities for fundamental research. Few-cycle laser pulse sources are now commercially available and are able to deliver energetic pulses (tens of micro-joules) at a MHz repetition rate. With such an extremely short pulse duration (<10 fs FWHM at 800 nm), the amount of energy required to reach the breakdown threshold in dielectrics is minimal, thus suggesting that few-cycle laser pulses are a very promising tool for reducing the heat affected zone and therefore the amount of thermo-induced stress during and after irradiation in transparent materials. In this article, the potential relevance of few-cycle laser pulses for microprocessing fused silica is examined. In particular, we demonstrate the fabrication of optical microstructures in the volume as well as on the surface of undoped fused silica.

In this study, novel annular microstructures on metal surfaces were fabricated with a femtosecond laser beam propagating through a microhole and irradiating on the surface of stainless steel SUS 304. The results showed that, with the use of a linearly polarized femtosecond laser beam (800 nm, 120 fs) irradiating through a microhole of diameter 80~100 μm and depth 800 μm, annular microstructures with a period of 4~8 μm were formed. Differing from the laser induced periodic surface structure (LIPSS), the formed annular microstructures are independent of laser polarization. This study speculates that this formation mechanism is due to the interference between the incident laser beam and the reflected beams from the microhole walls.

As a result of laser ablation, a surface roughness S_a between 0.4 μm and 2μm is obtained on 3D structures that have to be polished afterwards to meet customer requirements. For that reason a laser polishing process using ultrashort pulse laser sources is investigated. Applying the polishing process immediately after laser structuring in the same setting simplifies the process chain and saves both time and money. The results reveal an improvement of the surface roughness from an initial grinded surface with 0.4 μm to 0.2 μm by ultrashort pulse laser polishing. The productivity measured by the area that can be processed per time (polishing rate) is with 12.15 cm²/min one order of magnitude higher than state of the art laser polishing using nanosecond pulsed lasers.

Although there have been numerous attempts to define how different laser polishing parameters affect the generated surface roughness, there has been no detailed investigation of how their effects can be combined to optimize the process. This paper applies statistical analysis to model and predict the resulting surface roughness for laser post-processing of components made of Ti-6Al-4V and produced by laser powder bed fusion. This model is based on analysis of a wide ranging experimental programme investigating how the interaction of the governing parameters, i.e., laser power, number of repetitions, axial feed rate, scanning speed, and focal position, affected surface roughness. The experimental programme was the result of a robust Design of Experiments analysis and experimental analysis using ANOVA. It is expected that the outcomes will contribute towards the understanding of how the governing parameters influence the laser polishing process and final surface roughness, and would be a tool for optimizing their selection. The results of the ANOVA (analysis of variance) revealed that the most significant parameters are scanning speed followed by laser power and then axial feed rate. In addition, a clear tendency for the estimated Ra to decrease with the increase in laser power at lower values of axial feed rate and of scanning speed, and a focal position in the region of 2 mm. It is noted that the process parameters were varied over wide ranges, including extreme values, which made it difficult to accurately model the dependent variable over the full range of experimental trials.

We present a new fabrication method to realize smooth structures in lithium niobate. Therefore a detailed study on laser micro-polishing using ultrashort laser pulses is carried out by separating the effects of spatial pulse overlap and temporal pulse overlap. The adventage of this approach is the smoothing of the processed area by a simultaneous ablation. That will allow ablation depths between 1 µm and 4 µm with rms-roughness values of ≈20 nm.

The formation of laser-induced periodic surface structures (LIPSS) was investigated on different types of materials such as metals, glasses and composites. For this purpose, the broad spectrum of processing parameters (e.g., laser wavelength, beam polarization, peak fluence and pulse number) was used to precisely adjust the properties of the resulting ripple pattern. The formation process and potential applications were discussed, among other things, using the example of mechano-responsive changes in structural colors, heterogeneous wetting of substrate surfaces, and the tribological properties of composite materials selectively structured with LIPSS. Our studies provide qualitative insights into the LIPSS formation process and present potential applications of the structured surfaces in the fields of sensors, microfluidic devices, and implant materials.

This study describes the fabrication of dot and line-like periodic surface structures on metals, using new developed optical configurations based on Direct Laser Interference Patterning (DLIP). The optical setups are optimized for high throughput processing, for instance by shaping the beam profiles to elongated rectangular laser spots (with approximately 5.0 mm x 0.1 mm size) or by combining the DLIP optics with a scanner system. Later, aluminum and stainless steel substrates are processed using a nanosecond and picosecond pulsed laser source delivering up to 13 W and 180 W of laser power for the 10 ps and 10 ns systems, respectively. Depending on the pulse repetition rate applied and the pulse duration, a significant heating of the substrate volume was observed for the ns pulses. In this way, driven by Marangoni convection mechanisms, structures with exceptionally high aspect ratios could be produced. In case of the structures processed with ps pulses, large areas showing high pattern homogeneity were fabricated. Finally, water contact angle measurements of the produced structures are used to demonstrate the capability to control the surface wettability of the metals, even reaching super-hydrophobic conditions (using deionized water at room temperature). Also, the ability of the textured surface for increasing the freezing time of water droplets, and thus reducing ice-formation, is demonstrated at -20°C. Finally, the applicability of the DLIP scanner technology for decorative applications is shown. The characterization of the treated and untreated surfaces was performed using scanning optical microscopy and white light interferometry.

Single-pulse laser interference is applied to a Molecular Beam Epitaxy growth chamber to achieve in-situ patterning during the growth of III-V materials, with a focus on producing arrays of III-V quantum dots. We will describe the construction and characterization of the interference system as well as the in-situ patterning results. Pulsed laser interference is shown to strongly interact with the growing surface to produce periodic nanoscale features such as holes and islands, the nature of which is dependent on the local surface energy distribution. We describe a mechanism for the formation of these features in terms of surface diffusion under the influence of the periodic thermal gradient induced by the interference pattern. Nanoislands formed at the interference minima are shown to be ideal sites for quantum dot nucleation.

Ultrashort pulses incident on diamond generates a modulating surface relief referred to as laser induced periodic surface structures. The present work demonstrates the ability to tune LIPSS geometry as well as its areal syntheses, through appropriate choice of fabrication parameters. Rigorous Coupled Wave Analysis of LIPSS derived 1D grating on single crystal diamond surface revealed an enhancement in optical transmission. Fine-tuning the process conditions to pattern such 1D gratings on diamond surface and demonstrating its efficacy opens a relatively cost-effective route to engineer highly transmissive optical elements from diamond.

This Conference Presentation, “Surface structuring by high power femtosecond laser for industrial applications” was recorded at Photonics West LASE 2020, held in San Francisco, California, USA.

The use of pulsed laser irradiation techniques has proven to be a clearly effective procedure for the achievement of surface properties modification via micro-/nano-structuration, different conceptual approaches having been the subject of research and extensively reported in the literature. Beyond the broad spectrum of applications developed for the generation of structured surfaces of metallic materials with specific contact, friction and wear functionalities, the application of laser sources to the surface structuration of metal surfaces for the modification of their wettability and corrosion resistance properties is considered. Multi-scaled hierarchical surface microstructures fabricated on characteristic alloys (the concrete case of Ti6Al4V alloy is considered as example) by the combination of two complementary laser micro/nano-structuring techniques (Direct Laser Writing and Direct Laser Interference Patterning) are reported. Static contact angle measurements show a clearly hydrophobicity enhancement for both types of processing options and a clear improvement on the corrosion resistance of patterned samples of either type is observed. A discussion of the reported features in view of the applicability of the technique to industrial-scope problems is provided.

This study describes the implementation of a top-hat pulsed laser for high-throughput structuring using Direct Laser Interference Patterning (DLIP). Using two and four laser beams, dot and line-like periodic surface structures were produced, respectively. The top-hat laser profile allows treating the surface of the target materials without the need to overlap the different laser pulses and thus being capable of reducing the processing time compared to Gaussian energy distributions. Similarly, using a burst of pulses, the ablation efficiency of the DLIP process could be significantly improved. Finally, ablation tests on stainless steel samples are presented and discussed.

Recently, product protection and tracking became increasingly important due to the spread of piracy and counterfeiting. A common anti-counterfeiting procedure is embedding holographic motives or logos onto the good. If the motive is engraved directly onto the material surface, these features are inseparable from the good adding a higher degree of security. Holographic coloring is achieved by fabricating periodic surface structures, where the dimensions of the spatial periods lie in the order of the wavelengths contained in the visible spectrum. However, the fabrication of such periodic features directly on the product surface at high resolution and manufacturing speed is still challenging. Direct Laser Interference Patterning (DLIP) is an industrial compatible method with high processing flexibility which allows the structuring of holographic motives with high resolution and throughput. In this work, DLIP is employed to produce diffraction gratings with variable spatial periods and feature heights on a transparent PET substrate, which is a polymer commonly used for mass consumer goods and packaging. A numerical model based on the finite element method was used to restrict the gratings’ geometrical parameters that maximize the diffraction efficiency in reflection mode before their fabrication. Then, using the design of experiment approach, the laser processing parameters (laser power, pulse-overlap, spatial period) were selected in order to maximize the experimental first-order diffraction intensity, measured with a photospectrometer. The results allow to find the optimum set of parameters to fabricate homogeneous gratings with a first-order reflected intensity up to 4 % of the light source intensity.

Low-temperature poly-Si (LTPS) thin films formed by excimer laser annealing (ELA) are used as the channel material for thin film transistors (TFTs), which have an application as switching devices in flat panel displays. It is well known that one of the major problems in TFT manufacturing is the prominent ridges that form on LTPS thin films after ELA due to volume expansion by crystallization, which in turn induces gate leakage current in the TFTs. In this presentation, we report on the use of additional laser irradiation to reduce the height of the ridges and resulting changes in the electrical properties of LTPS-TFTs.

The advances in laser fabrication technologies have provided the means to create complex structural features in micro- and nanoscale. Hierarchical features, imitating natural materials, can be architected, providing remarkable mechanical performance. In addition, metamaterial structures, ranging from mechanical to bioengineering, with unprecedented properties, can be utilized for engineering applications. In this paper, we summarize conducted work on the laser-aided fabrication of architected structural and biological materials. To effectively design “meta-implants”, the design and structural principles encompassing these architected materials must be comprehended and substantiated. To this end, we fabricated by multiphoton lithography 3D mechanical metamaterial structures having as the principal objective to control failure and increase the strain energy capacity of the structure. New design concepts for 3D mechanical metamaterials were also introduced, exhibiting tailored buckling for enhanced strain hardening, high energy absorption and resilience to large deformations. Furthermore, we developed the processes required to create large scale bioscaffolds, that can be utilized in biological science and biomedical engineering for in vitro models.

The relentless demand for smaller and lighter products with faster and more powerful processing capabilities continues to be the overarching trend across nearly every sector of the electronics market: from telecom systems to medical sensors, image processing, and of course smart phones and devices. Today, advanced package integration (API) is arguably the key technological enabler supporting this trend, with a focus on vertical stacking platform – so-called 2.5D and 3D architectures – or fan-out wafer level packaging (FOWLP) as preferred in high bandwidth memory (HBM). An example of a true 3D package is where two (or more) thinned chips are stacked on top of each other in the same molded package, such as several memory chips or the combination of a logic chip and a memory chip. Excimer laser structuring offers multiple advantages in advanced packaging applications including ablation of vias and trenches, seed layer removal, and debonding. This technology is proven to provide a cost advantage for both current and future packaging applications. Whereas lithographic patterning involves photographic exposure of a resist, the excimer laser pulses directly remove material with virtually no peripheral thermal effects. A proven means to increase achievable field size is overlaying time-synchronized combined beams. Therefore, a sensitivity analysis of applying 308-nm excimer laser double pulses using various pulse delays on the key ablation parameters has been conducted.

Plasmonic materials have attracted great attention due to their ability to enhance light-matter interactions. Noble metals such as Au and Ag have been well studied as materials for plasmonic devices. However, these metals are not suitable for mid infrared (IR) plasmonic applications due to their relatively large optical losses, which are detrimental to device efficiency. Metal oxides, on the other hand, have been proposed for low loss metallic components in the mid IR because they can provide a tunable carrier density by varying the concentration of dopants or defects (oxygen vacancies). The epsilon-near zero wavelength of the real part of the dielectric permittivity of these metal oxides, for example, can easily be tuned from 1.5 μm to 4 μm by adjusting doping or defect levels. Optical losses in devices made from these metal oxide materials generally exhibit lower losses than those obtained with conventional metals. We have investigated laser processing techniques for synthesizing several types of metal oxides such as indium tin oxide and phase change materials such as VO₂. First, pulsed laser deposition was used to grow these oxide thin films. Second, an ultrafast laser was used to spatially pattern the thin films via a direct laser interference patterning (DLIP) configuration while simultaneously producing laser induced periodic surface structures (LIPSS) resulting in a uniaxial surface morphology. We will present details of the laser processing conditions on surface morphology, electrical, and optical properties of these laser processed metal oxide films.

Laser direct writing based on a graphene hybrid material was studied to develop the on-demand fabrication of an antenna-type sensor device related to IoT technology. A few-layer graphene oxide (GO) water dispersion formed a gel-like fluid and worked as a binder for CuO nanorods (NRs). A Go/CuO NRs hybrid coated flexible polymer substrate was scanned by a 445 nm semiconductor laser through a Galvano-scanner. Optical microscope images showed the Cu grain growth with increasing the laser power although a laser scanning under excess laser power condition formed an inhomogeneous film with the formation of an isolated large Cu grain. The laser-reduction of CuO NRs was enhanced by the presence of GO, which is an effective reductive agent for metal oxide nano-materials. Raman spectroscopy showed the formation of a reduced graphene oxide (rGO) and the disappearance of CuO signals in the Raman spectrum of a laser-scanned GO/CuO NRs hybrid film. The formation of metallic Cu from CuO NRs was also confirmed by XPS Cu2p spectra, which showed the disappearance of satellite peaks assigned to CuO. A meander line antenna pattern was drawn by laser direct writing on a GO/CuO NRs hybrid film and then unirradiated area was removed by water etching. The antenna-type sensor showed resonance peaks in the region from 1 to 6 GHz. The changes of resonance frequency and return loss were studied by dropping various solvents on the antenna-type chemical sensor. A resonance peak at around 5.50 GHz was sensitive to the dielectric changes depending on the solvents. A remarkable enhancement of the return loss and resonance frequency shift was caused by a solvent with the higher dielectric constant. The return loss change and dielectric constant of solvent showed a clear relationship.

Anti-wetting, or superhydrophobic surfaces have been a subject of significant interest in the engineering field for many years, particularly due to the potential to create self-cleaning surfaces. A droplet of water landing on a superhydrophobic surface will roll or slide away, whilst taking with it any surface debris. Such surfaces exist in nature, and there have been many reports where ultra-short pulsed lasers have been used to generate surfaces with similar feature sizes and hydrophobic performance. However it is also possible to produce superhydrophobic surfaces with short (nanosecond) laser pulses. In this paper we report our work in which flat sheets of SS304S15 were textured using a nanosecond pulsed fibre laser operating at 1064 nm. Quantitative analysis of the wettability of the laser structured surfaces was carried out by measuring the static contact angle of a droplet of deionized water with a volume in the microliter range. As with other reports, these surfaces are initially hydrophilic, and after a time delay of some days to weeks transition to hydrophobic, and in some cases to superhydrophobic. In order to realise a practical process, our work has concentrated in speeding up this transition from weeks to days, and to this end we have studied the role of the processing environment during laser texturing.

Carbon fiber reinforced polymer (CFRP) offers the highest potential for lightweight applications due to its excellent weight to strength ratio in comparison to other materials. However, it is cost-intensive and therefore rarely used monolithically. This makes pretreatment and joining processes so important. Hybrid connections of CFRP and metals can be made by riveting, bolting, stir joining and by adhesive. For adhesive bonding, a pretreatment of the materials is necessary. A laser pretreatment has the advantage, that it is automatable and contactless. This paper deals with the pretreatment of CFRP with different laser wavelengths in near-infrared (NIR, 1030 and 1064 nm) and ultraviolet (UV, 355 nm) range. The influence of the processing direction relative to the fiber layer and the influence of the energy density was investigated with a short pulsed NIR infrared laser. In addition, the influence of different surface structures on the mechanical strength was investigated. The treated CFRP surfaces were examined with a light microscope and a scanning electron microscope. The tensile shear strengths were determined using CFRP and aluminum substrates, joined with a 2-part epoxy adhesive. As a comparison, UV laser treated specimens were also mechanically tested. An ultra-short pulsed NIR laser system was used to generate periodic structures on the CFRP to maximize the surface area without fiber damage and breakage. The investigations on the influence of the machining direction with NIR relative to the fiber layer showed insignificant differences in shear strengths. The variation of the energy density showed an influence on the ablation behavior of the CFRP matrix and the mechanical strength. The maximum strength with a cohesive failure in the adhesive was achieved with optimized short pulsed NIR laser parameter.

Recently, we proposed using embedded nanogratings to change the polarization state in fused silica femtosecond laser direct written optical circuits. Full control over the elements’ birefringence properties can be attained by changing the inscription parameters and using a suitable writing geometry. Therefore, these structures can be used to arbitrarily transform the polarization state on an optical chip. Due to the intrinsic birefringence of these structures, the required length of the functionalized section is only a few hundred micrometers. We demonstrated four single qubit quantum gates based on these structures (Hadamard, Pauli-x, Pauli-z and Pi-8th). However, the overall losses of these structures are still rather high. We present our endeavour to reduce the losses by using adapted beam shaping. The improved performance and their potential for optical quantum computing will be presented.

Generation of nano or micro-scale structures on materials surface enables new functions and properties, such as super-hydrophobicity by lotus effect, surface blackening by light trapping, modification of surface tribological properties, etc. which are in high demand for a wide variety of industrial fields. Amongst the surface functionalization techniques, Ultra-Short Pulse lasers have been proven to be a reliable tool to create Laser Induced Periodic Surface Structures (LIPSS). Exploitation of LIPSS for industrial purposes poses some key problems like up scaling over large area with high repeatability and high throughput. Beam shaping could be a key element to overcome these issues. Specific shapes, such as top-hat line shape, could enable at once uniform processing over large surface with the consequence to reduce the processing time. Multi-Plane Light Conversion (MPLC) is an innovative technique of beam shaping which allows theoretically lossless complex beam shapes with a high control over amplitude and phase. The free-space reflective design allows for high beam shaping quality whilst maintaining the ultra-short property of the laser pulses, which is not usually achievable through other beam shaping methods. Here we show the results obtained over Stainless-Steel using an industrial femtosecond laser with a tophat line of 30μm × 594 μm intensity profile generated using MPLC technology. The beam has been delivered over the Stainless-Steel surface with a galvo scanner and focused through an f -theta lens of 100 mm. Surface morphology has been investigated via SEM and the processing time has been compared to conventional round Gaussian Beams

Lab-on-a-Chip (LoC) systems are utilized for medicine and biotechnology applications. The field reaches from synthesis of active pharmaceutical ingredients up to the detection of specific biomarkers and the cultivation of human cells and human tissues for substance testing, personalized and regenerative medicine. LoC systems can be realized quickly and flexibly with an established closed technology chain developed at Fraunhofer IWS. In the first step, the system is constructively split into individual layers, which are later formed in each case by a separate foil. In the second step, a material with the desired properties is selected from the functional boundary conditions for each layer. In the third step, the foils are cut by means of laser micro-material processing, structured on both sides and optionally functionalized. In the fourth and final step, the individual foils are laminated together into a multilayer system using different technologies. In order to increase the effectiveness of laser micro-material processing, the established scanner-based optical design was further developed. The f-Theta lens was removed and replaced by a dynamic beam shaping element and a fixed focal length lens located in the beam path in advance of the scanner (“post-objective scanning”). As a high-dynamic beam shaping module, a mirror with piezo-driven surface curvature is used. The focal spot can be placed in a plane via a defined curvature as a function of the scanner mirror positions. By eliminating the f-Theta objective, the working area is increased by a factor of 4, resulting in a total process efficiency improvement.

Non-diffracting Bessel beams and its modified versions are widely used in industry for transparent material micro processing purposes - cutting, drilling etc., due to generation of high aspect ratio micro voids. More and more applications of such beams involve manipulation of their transverse intensity profile to create unique tools for novel micro processing applications, for example, asymmetric and multi-peak transverse profiles create directional strain and crack in modified area for glass cutting, while other intensity patters may be used to create complex structures in multiphoton polymerization applications. In this work we demonstrate experimental generation of higher order vector Bessel beams which are notable for their ring-shaped transverse intensity profile together with multi-peak transverse polarization components, where ring diameter and number of peaks in separate polarization components depends on beams order. These unique beams were realized using axicon together with higher order s-plates - spatially variant waveplates based on femtosecond laser written nano gratings in fused silica glass substrates. Induced nanogratings withstands high intensity laser radiation without changing its spatial structure which allows us to use nanograting based elements for ultra-short high-power pulsed laser beam shaping. Generated higher order vector Bessel beams and their separate polarization components were used to inscribe modifications in transparent materials and to investigate beam`s applicability for ultra-fast laser micro processing purposes.

Here, we demonstrate the benefits of acousto-optic deflector (AOD) technologies for advanced spatio-temporal beam control in CO2 via drilling. Spatially, we demonstrate the ability to drill multiple via sizes on the fly, enabling the drilling of multiple via sizes on one panel within one single pass. Temporally, we demonstrate the ability to slice one laser pulse into multiple sections, enabling fine-tuning of the pulse energy profile delivered to the workpiece. Furthermore, we compare via drilling results using AODs to those drilled with traditional punch processes, showing advantages in both throughput and quality in comparison to traditional imaging-based CO2 drilling systems.

Ultra-fast laser in micromachining have a reputation of highest precision and quality, which justifies additional invest in numerous applications. However, deficits in the synchronization of the positioning of beam deflection device and laser triggering -in particular at high repetition rates- still lead to defects like overtreatment due to the inertia of the mirrors of galvanometer scanners or path deviations at complex shapes. This in turn has led to an increasing demand of advanced pulse to pulse control for precise laser energy deposition. Two recent innovations have the potential to overcome these current limitations. Firstly, the scan ahead feature allows to calculate the actual beam position in acceleration and deceleration mode. According to the precise position feedback the control needs to adjust the repetition rate of the laser source e.g. at rectangular corners of a scan trajectory. Therefore, the pulse on demand feature at the laser interface is obligatory to dynamically adjust the pulse to pulse delay in order to accomplish constant energy deposition at any programmed scan pattern. We have put these two innovations to a test by combining an Excelliscan from Scanlab with an UV Tangor laser from Amplitude to validate the synchronization and constant pulse separation at various scan speeds and geometrical patterns. Applications trials like engraving with scan speed are presented in comparison to conventional scanning techniques to demonstrate the benefit of the fast synchronization and pulse on demand technologies.

In micro-material processing with ultrashort laser pulses (USP), the surface quality during drilling and thin film ablation varies with the scanning speed and the pulse repetition rate. However, while high pulse repetition rates tend to be desirable, local heat accumulation caused by increasing pulse overlap is counterproductive. Thus, the scanning speed must be scaled with the pulse repetition rate, preferably by supplementing the already existing setup.

In this work, we present a dynamic extension through the combination of an acousto-optical deflector (AOD) with a galvanometer scanner. This combines the best of two worlds: the dynamic beam deflection of the AOD and the large scanning field of the galvanometer scanner. The integrated AOD is able to deflect the laser beam pulse by pulse within its scanning field and to modulate the beam intensity simultaneously. The mechanical limitations and problems of the galvanometer scanner, such as vibrations and overshoots due to fast mirror rotations, can be specifically compensated by the high precision of the AOD. As a result, in addition to process time reduction, the surface and image quality improves significantly. In any case, the laser source needs synchronization with the AOD because the propagation of sound waves within the AOD crystal is slower than the laser pulse propagation through the medium. In the first step, a comparatively slow AOD based on tellurium dioxide with a transversal crystal alignment is used. The process time of a thin film ablation with 4 μJ at 1 MHz was reduced considerably by applying a USP laser system (Coherent Monaco).

The recent developments in high-speed laser machining combine high-average power lasers with ultrafast beam deflection systems.1 However, when using ultrashort pulses at megahertz pulse repetition frequencies the incoming laser beam may interact with the plasma/particle ablation plume that is due to the very short time intervals between the impinging megahertz-repetitive pulses. Thereby, the subsequently irradiated pulses will either be reflected, absorbed and/or scattered by the still existent plasma/particle plume as induced by the previously irradiated pulse(s). This shielding of the incoming laser beam is adversely affecting material ablation and can potentially be avoided when the beam is ultrafast moving in front of the emerging plasma/particle plume. For the real-time analysis of such fairly unknown processing regimes, a pump-probe shadowgraph imaging technique was used to visualize laser materials interaction in high-speed ultrashort pulse laser machining. The pump laser source supplied a beam of λ=1030 nm, ƬH =600 fs and 48MHz maximum pulse repetition frequency for material ablation. A diode laser system provided the probe beam of λ=688 nm and ƬH =13 ns. The pump and the probe beam could be electronically delayed within a time frame of up to 10 µs. Sequences of shadowgraphs will be presented to visualize plasma/ablation plume expansion for providing unique insights into high-pulse repetition frequency ultrashort pulse laser materials interactions at ultrafast laser beam movements above 250m/s. The shadowgraphs reveal that the form of the emerging plasma/particle plumes is influenced by the laser beam moving speed. The plumes vary in their density and structure from clearly distinguishable at highest speed, through smoothly detached to be turbulent. In addition, it is shown on the shadowgraphs material ejection takes place at the time when the ultrafast scanned laser beam moved away from the initial irradiation area.

During the last decades laser micromachining became a valuable tool for many applications in automotive, medicine, tool construction, or mobile technology. Beside the quality, processing time and production costs are crucial questions. A promising approach to achieve high throughput combined with good processing quality represent laser ablation by an assisting magnetic-field. Therefore, we studied the influence of an applied magnetic field to the ablation behaviour of silicon by using short and ultrashort laser pulses. Based on the experimental results we report on a first theoretical model that addresses the energy distribution of the heated electrons in the irradiated area.

We report the analysis of femtosecond laser modification of poly(methyl methacrylate) (PMMA) by detection of optical signals emitted from the sample coaxially with laser beam. The influence of pulse duration, energy and burst pattern on recorded spectra was investigated using TruMicro 2000 laser. We present images of internal structures in polymer as well as the spectra of conical emission created as result of laser – polymer interaction. Generation of a broadband continuum signal was detected and analysed in a function of position of the focal plane. Furthermore, third harmonic generation and second harmonic of fundamental 1030 nm wavelength was detected and the origin of these signals is discussed. We present possibility of the material modification process monitoring by in situ spectral analysis of light coming out from the sample. The deposited pulse energy fraction was analysed.

Lab-on-chip systems are based on components to transport, mix, separate and analyse small volumes of different fluids. The consecutive integration of more complex functions into a single and compact chip demands on multilayer systems. As the classical production using a stacking and joining of single processed layers is elaborate and limited in terms of multilayer structures, an uprising trend to fabricate those devices is the internal, three dimensional processing of transparent substrates by using ultrashort laser pulses. In this study, we report on the generation of internal hollow architectures created by focused 514nm femtosecond laser pulses inside optical polymer bulk materials of different polymers. The three-dimensional channel layout is implemented by moving the sample using three-dimensional motorized stages, allowing arbitrary complex shaped internal channel architectures. Size and cross sectional shape of a single internal generated microchannel are determined by the intensity distribution of the focal voxel. In particular, we show a comprehensive parameter study to improve this laser process with respect to a higher processing speed and stability.

The Laser Micro-Jet® is now a well-established technique for micro-machining and high-quality machining of hard materials. The advantages of the water-jet guided laser ablation are narrow parallel cut walls without focus adaptation, minimizing the heat-affected zone by the water cooling and the avoidance of burrs due to constant water flow.
To further enhance this innovative technology towards industry 4.0, automation and sensing packages have been implemented into the CNC platforms. Ease of use measures include self-calibration by an automatic adjustment of the water jet angle and an automatic alignment of the laser beam into the waterjet nozzle, guaranteeing precision.
The process has become self-correcting by adding a break-through sensor, which detects the end of cutting or drilling by a change in the processing light when the laser fully traverses the material. The suppression of unnecessary extra passes leads to a diminution in overall processing time, in some cases up to 20 %, additionally the cutting defect rate drops below 1%.
The integration of an automatic jet laminarity sensor adds the ability to detect waterjet degradation over time and is the first step towards machine self-check. Finally, Synova is developing automatic 3D-machining with depth sensing capabilities for a controlled and feed-backed ablation of 3D-profiles. An intelligent choice of toolpath, adapted to the LMJ-technology, will further advance feedforward machining capabilities.

In forming processes, lubrication is used to reduce friction and wear occurring at the contact areas of workpiece and tool, by separating these surfaces as well as transporting abrasive wear out of the sliding interface. With high interest in waste avoidance and efficient use of resources, today’s industry aims for substituting this lubrication. Thereby, deposition of surface coatings or local surface structuring offer a different way for friction reduction in forming processes. In this work, the flange area of a deep drawing tool is firstly macro-structured by milling process to decrease the contact area to the workpiece by 94%. Additionally, the pulling edge radius is coated with a hydrogen-free ta-C layer with sp³-ratio of 70%. Subsequently, the coated area is micro-structured employing Direct Laser Interference Patterning (DLIP), introducing well-defined contact areas to decrease friction and wear by locally rehybridizing the ta-C material. Also, the high-speed DLIP micro-structuring of the workpiece metal sheets is made to further reduce the contact area and lower the friction. Forming of test strips show the influence of the macro-structured flange area by reducing the friction force down to 75%. Performed tensile-bend tests on micro-structured ta-C coated cylinders could show a reduced coefficient of friction, small wear volume and resistant DLIP structures after the tribological evaluation.

Sandblasting is an established technique in generating surface textures on titanium and other metal alloys; these surfaces are desirable in the field of biomedical engineering as they promote osseointegration of medical implants. However, this process has significant limitations including, the embedment of abrasive particles causing changes to surface composition, lack of automation, and health hazards. Laser processing is becoming more common in the medical industry as a method to generate surface textures. Nanosecond laser systems are generally used in surface processing for their benefits of productivity and cost; however, the ultra-short pulsed lasers induce less thermal damage. This study probes the use of stochastic laser processing (laser-blasting) as an alternative to sandblasting to modify surfaces of Ti₆Al₄V. Laser processing parameters such as power and pulse durations were investigated in both nanosecond and femtosecond laser systems operating in the IR region. Surface morphology and microstructural changes of laser blasted samples were inspected using a variety of techniques (confocal microscopy, SEM and EDX) and then compared with those that had been sandblasted. The results obtained show that through careful selection of parameters, laser-blasting is capable of generating similar surfaces produced by sandblasting with limiting thermal damage.

Long focal lines with transverse spot sizes as small as a few wavelengths are called optical needles. A zeroth order Bessel beam being a good example is widely used in such applications as laser micromachining. In practice Bessel beam generated with an axicon has a peak in axial intensity distribution and is not only due to aberrations caused by planar dielectric material interface. Here, we investigate optical needles with controlled axial intensity distribution via intensity modulation of the incoming beam. We have chosen to generate constant axial intensity Bessel beam and propose spatial transmission mask to do so. Experimental verification is presented using diffractive optics elements based on Pancharatnam-Berry phase. We demonstrate a flattening of the axial intensity profile of the Bessel beam without the alteration to the optical needle diameter.

GFH GmbH has developed a helical drilling optics, which rotates the beam up to 30.000 rpm and allows furthermore to adjust the diameter and the incidence angle. This enables the laser to be used for high precision drilling and cutting and micro turning processes.

Metal enhanced fluorescence is a phenomenon that occurs when a fluorophore is positioned near a conductive structure. Structures can be formed by the interaction of high-energy laser with a sample, on which the femtosecond laser pulses interact with the surface without heat effects. This work aims to study nanostructure formation in polished bulk silver, in order to amplify signals of fluorescence. A Titanium-sapphire femtosecond laser was used to mark silver surfaces. SEM images shows nanostructures formed in chaotic agglomerate of nanospheres with size of 50-800nm. Using Protoporphyrin-IX, the fluorescence amplification was around 300 times compared to a surface without the nanostructures.

In this contribution, Cr stamps were structured with periodic hole-like arrays using Direct Laser Interference Patterning. Using optimized laser processing parameters, homogeneous textures with different spatial periods and aspect ratios were produced, as observed with confocal microscopy. Then, these stamps were used as molds for patterning transparent polymers, namely polyethylene terephthalate (PET), poly(methyl methacrylate) (PMMA) and polycarbonate (PC) by plate-to-plate hot embossing. Adjusting the imprint time and temperature, replicas of the Cr stamps were fabricated reproducing faithfully the mold shape. Static water contact angle (WCA) measurements were done to study the wettability properties of these structured polymers. The results show that the produced topographies increase the WCA compared to the flat references up to an absolute maximum of 55° in the three polymers. For instance, a PET foil structured with a spatial period of 4.7 μm and a structured depth of 3 μm showed a WCA of 139° representing an increase of about 70% compared to a flat sample. The diffraction intensity of the patterned polymers was measured with an imaging optics and a spectrometer coupled to a goniometer in order to characterize their optical properties. It was found that for those samples processed with 80 or less applied laser pulses the diffraction peaks are clearly identified, whereas for large number of pulses there is more diffuse light travelling along random directions and the diffraction peaks become less defined. In conclusion, enhanced wettability and optical functionalities were achieved in transparent polymers imprinted with periodic microstructures.

Laser processing in the market is required with high precision and fast speed in large area without stop. In order to do this technology, it is essential to synchronize scanner and stage and it is able to process large area exceeding optical field size by scan lens. Additionally, this processing is very important to stabilize and optimize optical system such as laser optic and vision for high precision and fast speed. So, we developed a complex laser processing system for cutting and drilling etc, and then we tested various laser applications using the developed complex laser processing system. So in this paper, the various functions and performance of the developed complex laser processing system are described, and the laser application results will be introduced.

Hyperbranched polyethylenimine coated zinc selenide (PEI-ZnSe) quantum dots were synthesized by femtosecond laser ablation in microfluidics. The PEI-ZnSe aqueous dispersions showed a strong green fluorescence at 500 nm. Based on Density functional theory, the defect energy level characteristics of different point defects in the Se-rich ZnSe quantum dots were studied. The results show that the shallow acceptor levels close to HOMO will be introduced into the bandgap by Se interstitial point defects, and the deep acceptor level close to LUMO will be introducted into the badgap by Se antisites point defect. According to the calculation results of defect energy levels, the energy level transition mechanism of quantum dot absorption and fluorescence emission were analyzed, and the types and quantities of defects existing in the quantum dots are discussed. The results show that the prepared PEI-ZnSe organic composite quantum dots have a large amount of Se_Zn and Se_i defects, and the green fluorescence near 500 nm is the defect level luminescence (Se_Zn → Se_i).