Ultrashort Pulse Laser Technology Research Articles

Dissociation dynamic study of <inline-formula><tex-math id="M2">\begin{document}$\text{H}_2^+$\end{document}</tex-math></inline-formula> in time-delayed two-color femtosecond lasers

In recent years, the rapid development of ultrashort pulse laser technology has made it possible to regulate the ionization and dissociation dynamics of atoms and molecules. Among them, the microscopic dynamics of molecular dissociation have always been a hot topic. The phenomenon of molecular dissociation, which is caused by the interaction between femtosecond intense laser fields and <inline-formula><tex-math id="M3">\begin{document}$\text{H}_2^+$\end{document}</tex-math></inline-formula> molecules, has attracted widespread attention. Previous theoretical studies on the dissociation of <inline-formula><tex-math id="M4">\begin{document}$\text{H}_2^+$\end{document}</tex-math></inline-formula> molecules mainly focused on studying its dissociation dynamics through numerical calculations, with relatively few theoretical models. This paper aims to establish a simple classical model to describe the dissociation dynamics. Firstly, this paper calculates the joint distribution of nuclear energy and electronic energy in the dissociation process of <inline-formula><tex-math id="M5">\begin{document}$\text{H}_2^+$\end{document}</tex-math></inline-formula> molecules under the action of pump lasers by numerically solving the Schrödinger equation. The results prove that <inline-formula><tex-math id="M6">\begin{document}$\text{H}_2^+$\end{document}</tex-math></inline-formula> molecules initially in the ground state are dissociated into <inline-formula><tex-math id="M7">\begin{document}$H^+ + H^*$\end{document}</tex-math></inline-formula> after absorbing a pump photon in the pump light field. Next, this paper studies the dissociation dynamics of <inline-formula><tex-math id="M8">\begin{document}$\text{H}_2^+$\end{document}</tex-math></inline-formula> molecules in time-delayed two-color femtosecond lasers. We find that it greatly depends on the specific forms of the pump light and the probe light. By utilizing the dependence of the dissociation kinetic energy release (KER) spectrum on the time delay of the two-color femtosecond lasers, we retrieve the sub-attosecond microscopic dynamic behaviors of electrons and atomic nuclei in the dissociation process. Furthermore, we establish a classical model based on the conservation of energy and momentum to describe the dissociation dynamics. This model can qualitatively predict the ion dissociation KER spectrum depending on the time delay of the two-color femtosecond lasers. The electronic resonant transition between the molecular ground state and the first excited state caused by the probe light will affect the ion kinetic energy spectrum in the dissociation process. Namely, the ion kinetic energy spectrum is dependent on the frequency of the probe laser. By taking advantage of this characteristic, we propose a scheme to reconstruct the evolution of the internuclear distance with time. Our reconstruction results can qualitatively predict the trend of the numerical simulation results, and this scheme may provide some theoretical guidance for experiments.

Methodic development of laser micro structured cutting tools with microscale textures for AW7075 aluminum alloy using a Plackett–Burman screening design

In this paper, the effect of microscale structures on the tribological and cutting behavior of cutting tools has been evaluated. A method for developing the micro structure design is presented using a statistic screening design. The micro structures are applied using ultrashort-pulsed laser technology. The effects of different structural parameters are investigated in orthogonal cutting of AW7075. Tools with structures benefit from lower cutting forces and exhibit a shorter chip morphology.

Novel layered 2D materials for ultrafast photonics

Abstract A range of new 2D materials have recently been reported, including topological insulators, transition-metal dichalcogenides, black phosphorus, MXenes, and metal-organic frameworks, which have demonstrated high optical nonlinearity and Pauli blocking for widespread use as saturable absorbers in pulsed lasers. 2D materials are emerging as a promising platform for ultrashort-pulse fiber laser technology. This review presents a catalog of the various pulsed laser applications based on the series of emerging 2D materials. In addition, novel optical devices using layered materials, such as optical modulators, optical switches, and all-optical devices, are also included. It is anticipated that the development of 2D materials will intensify in the future, providing potentially new and wide-ranging efficacy for 2D materials in ultrafast photonic technology.

A neutron-diagnostic method using a BF3 detector array for ultrashort-pulse-laser neutron sources in strong gamma-ray environments

With the rapid development of ultrashort-pulse laser technology, short-pulse, high-flux neutron sources based on the interactions of laser plasmas have become increasingly important. However, the extremely strong gamma rays generated by the interaction between a picosecond laser beam and a target make it difficult to apply traditional neutron-diagnostic methods. Here, we introduce a neutron-diagnostic method that employs a BF3 detector array for use in the strong-gamma-ray environments associated with ultrashort-pulse-laser neutron sources. This method determines the neutron yield by collecting signals from each of six independent BF3 counting tubes, effectively reducing statistical-fluctuation uncertainties. We first propose a time-partition calibration method for the BF3 detector array that uses counts in different time intervals. With this calibration method, the dynamic range for neutron-yield measurements is expanded from 1× 103∼ 1× 108 to 1× 103∼ 1× 1010 neutrons (in 4π space). We have applied this neutron-diagnostic method for the first time to the ultrashort-pulse-laser neutron source at the SG-II upgrade facility.

Toward the medical application of non-labeled spectroscopic imaging using ultrashort pulse laser technology

Toward the medical application of non-labeled spectroscopic imaging using ultrashort pulse laser technology

Fabrication of a ball end nose micro milling tool by tangential laser ablation

The general trend towards miniaturization of components is leading to an increasing demand for micro cutting tools. Such tools are found in a variety of applications like optics manufacturing, mold machining or medical technology. Indeed, micromachining exhibits a high efficiency, accuracy and low cost in comparison to other micro processing technologies. Micro cutting tools are mostly produced by grinding, a mechanical process, which might damage the tool due to induced forces, vibrations and heat. These detrimental effects cause the high scrap rate in the manufacturing of micro cutting tools and limited geometrical flexibility. A new approach for the manufacturing of micro cutting tools is given by the ultrashort-pulsed laser technology: it enables material removal, which is independent of the hardness of the workpiece material and with only a negligible heat-affected zone. In most cases, laser ablation is disadvantaged in contrast to grinding because of its relatively low material-removal rate. When it comes to the manufacturing of micro cutting tools the small amount of material to be removed makes the ultra-short pulsed laser an interesting alternative to grinding. Furthermore, the laser ablation is a force and wear-free process, which ensures high precision. In this paper, a commercially available micro ball end mill geometry is measured by micro X-ray tomography and 3D microscopy. The movement of the mechanical axes and the path of the laser beam for manufacturing the desired tool are determined based on these measurements. The milling tools with a diameter of 100 µm are produced from cemented carbide blanks, on a 8-axis laser machining center. After machining, the tools are analyzed by SEM and using FIB: By creating a cross section perpendicular to the cutting edge the heat-affected zone is examined. Finally, the cutting tool is successfully applied for the manufacturing of micro electrodes in copper for an EDM process while recording the cutting forces.

Selective photonic disinfection of cell culture using a visible ultrashort pulsed laser.

Microbial contamination of cell culture is a major problem encountered both in academic labs and in the biotechnology/pharmaceutical industries. A broad spectrum of microbes including mycoplasma, bacteria, fungi, and viruses are the causative agents of cell culture contamination. Unfortunately, the existing disinfection techniques lack selectivity and/or lead to the development of drug-resistance, and more importantly there is no universal method to address all microbes. Here, we report a novel, chemical-free visible ultrashort pulsed laser method for cell culture disinfection. The ultrashort pulsed laser technology inactivates pathogens with mechanical means, a paradigm shift from the traditional pharmaceutical and chemical approaches. We demonstrate that ultrashort pulsed laser treatment can efficiently inactivate mycoplasma, bacteria, yeast, and viruses with good preservation of mammalian cell viability. Our results indicate that this ultrashort pulsed laser technology has the potential to serve as a universal method for the disinfection of cell culture.

High-rate laser microprocessing using a polygon scanner system

This paper discusses results obtained in high-rate laser microprocessing by using a high average power high-pulse repetition frequency ultrashort pulse laser source in combination with an in-house developed polygon scanner system. With the recent development of ultrashort pulse laser systems supplying high average power of hundreds watts and megahertz pulse repetition rates, a significant increase of the productivity can potentially be achieved in micromachining. This permits upscaling of the ablation rates and large-area processing, gaining increased interest of the ultrashort pulse laser technology for a large variety of industrial processes. However, effective implementation of high average power lasers in microprocessing requires fast deflection of the laser beam. For this, high-rate laser processing by using polygon scanner systems provide a sustainable technological solution. In this study, a picosecond laser system with a maximum average power of 100 W and a repetition rate up to 20 MHz was used. In raster scanning using the polygon scanner, the laser beam with a focus spot diameter of 44 μm was deflected with scan speeds of several hundred meters per second. The two-dimensional scanning capability of the polygon scanner supplied a scan field of 325 × 325 mm. The investigations were focused on high-rate large-area laser ablation of technical grade stainless steel as well as selective thin film ablation from bulk substrates. By variation of the processing parameters laser fluence, as well as temporal and spatial pulse-to-pulse distance, their impact onto the ablation process was evaluated with respect to the ablation rate, processing rate, surface quality, and ablation efficiency.

Functionalization of surfaces by ultrafast laser micro/nano structuring

In surface functionalization, micro- and nanotexturing with ultrashort pulse lasers is of increasing interest in industry. These two scales of structures can be obtained by a selforganization of the matter after laser irradiation, or by a micro-machining of the sample with successive ablations. Controlling key-parameters such as wavelength, laser fluence, spot overlap, number of repetitions and polarization, allows the generation of self-organized nanostructures called ripples or the creation of square-shaped micro-structures. In the first case, a surface textured with these nano-gratings presents a diffractive aspect or a permanent marking, but changes little the initial wetting behaviour of the surface. In the second case, the microstructures improve significantly the wettability of the surface, with an increase of almost 20° of the contact angle with a water droplet. So a large range of surface texturing can be performed with ultrashort pulsed laser technology, offering a wide range of applications, from biomedical to aeronautical.

Lasergesteuerte Probenpräparation von Hartgeweben und Biomaterialen

In tissue engineering multiple tasks have to be solved: from cell isolation for cultivation to histological sections of implants in animal models. However, it still lacks proper tools to section and image biomaterials and tissue for histology, 3D-culture or further biochemical analysis. This article describes the use of ultrashort pulse laser technology for sectioning for sample preparation. Integration of imaging technologies facilitates deep tissue imaging and guided cutting.

Cool Laser Pulses

AbstractDuring the past decades pulsed laser systems have motivated many novel laser material applications. Nowadays ultrashort pulse (USP) lasers are routinely used for machining and processing high‐tech materials like glass, sapphire or ceramics and allow the production of small and powerful smart phones, high efficient solar cells or medical devices. The next generation USP lasers will focus on smaller system dimensions, a reduced price and shorter pulses to allow for even higher precision and smaller structuring. The article will give an overview of USP laser technology and concepts for future system configurations.

Optical pump-probe scanning tunneling microscopy for probing ultrafast dynamics on the nanoscale

The development of a method for exploring the ultrafast transient dynamics in small organized structures with high spatial resolution is expected to be a basis for further advances in current science and technology. Recently, we have developed a new microscopy technique by combining scanning tunneling microscopy (STM) with ultrashort-pulse laser technology, which enables the visualization of ultrafast carrier dynamics even on the single-atomic level. A nonequilibrium carrier distribution is generated using ultrashort laser pulses and its relaxation processes are probed by STM using the optical pump-probe method realized in STM by the pulse-picking technique. In this paper, the fundamentals of the new microscopy technique are overviewed.

Experimental Investigations Concerning the Sensitivity of the Leakproofness Test for Dangerous Goods Packagings Relating to the Leak Diameter

The objective of this experiment was to verify that in regards to the leakproofness bubble test for packagings of dangerous goods, a reduction of the air overpressure from 0.2 to 0.1 bar can be compensated for by reducing the water surface tension to a value of approximately 33.2 mN/m by adding a wetting agent. It was experimentally proven that this method will yield the same leak diameters. This is important to avoid irreversible deformations during the leaktesting of intermediate bulk containers (IBCs) while using a test overpressure of 0.2 bar. Bubble test experiments were carried out on artificial borehole-shaped leaks manufactured of two different materials high density polyethylene (HDPE) and stainless steel by ultrashort pulse laser technology and with two different immersion test liquids (deionized water and a 0.1% Lutensol FSA fabric softener active 10 solution). The characteristic diameters of the boreholes investigated were from 11.5 to 30.3 µm in length. Copyright © 2013 John Wiley & Sons, Ltd.

Prospects for a novel ultrashort pulsed laser technology for pathogen inactivation

The threat of emerging pathogens and microbial drug resistance has spurred tremendous efforts to develop new and more effective antimicrobial strategies. Recently, a novel ultrashort pulsed (USP) laser technology has been developed that enables efficient and chemical-free inactivation of a wide spectrum of viral and bacterial pathogens. Such a technology circumvents the need to introduce potentially toxic chemicals and could permit safe and environmentally friendly pathogen reduction, with a multitude of possible applications including the sterilization of pharmaceuticals and blood products, and the generation of attenuated or inactivated vaccines.

Konzept eines druckgesteuerten Mikrostents für die Glaukomtherapie

A pressure-controlled microstent could permanently normalise the intraocular pressure (IOP) for open-angle glaucoma therapy by drainage into the suprachoroidal space. The complex requirements demand new technical solutions as well as an improved understanding of specific cell biological processes at the implant's surface to develop effective local drug delivery (LDD) concepts and surface modifications. Fluid mechanical requirements were derived from physiological data and the analysis of commercial glaucoma implants. The technological basics for the production of suitable structures are refined ultra-short pulse laser technology and 2-photon polymerisation (2PP). All known glaucoma implants induce unwanted cell proliferation resulting in a loss of function. It is assumed that the activity of fibroblasts is low in the suprachoroidal space. However, it was seen that LDD concepts are required to control cell proliferation. Fibroblasts from sclera and choroidea were isolated und cultured as the most relevant cell types for in vitro investigation. Potential materials and drugs were investigated by cell viability tests for biocompatibility or suppression of cell viability. The fluid mechanical analysis leads to smallest stent lumina (ID = 50 µm) at anatomically suitable implant lengths (7 - 10 mm). Only pressure control can manage the individual conditions with changing IOP. Finite element analysis of valves showed the need for highly flexible structures. This can be achieved by combining basic structures with micromechanically active valves added by 2PP. The potential materials show perfect in vitro and in vivo biocompatibility. Ormocers which are best suited for 2PP are also highly biocompatible. The selected drugs paclitaxel and triamcinolon acetonide open a wide therapeutic window to impair fibroblast growth. The surgical procedure was established by implantation of prototypes in rabbit eyes, connecting the anterior chamber with the suprachoroidal space. Highly flexible implants are required for correct placement within the eye. The new concept of the microstent combines biomechanical approaches, technologies for microfabrication and current LDD concepts and opens new perspectives for glaucoma therapy.

Real-space imaging of transient carrier dynamics by nanoscale pump–probe microscopy

By combining advanced ultrashort-pulse laser technology with scanning tunneling microscopy, scientists demonstrate that they can directly image transient carrier dynamics in nanostructures in real space.

Selective Inactivation of Viruses with Femtosecond Laser Pulses and its Potential Use for in Vitro Therapy

Introduction: Traditional biochemical and pharmaceutical methods employed today encounter problems of clinical side effects and drug resistance, and their use is becoming limited. Therefore, it has become important and necessary to develop new, alternative strategies to combat viral diseases.Materials and Method: A variety of viruses including M13 bacetriophage (nonenveloped ssDNA), tobacco mosaic virus (nonenveloped ssRNA), human papillomavirus (nonenveloped dsDNA) and human immunodeficiency virus (enveloped ssRNA), together with human red blood cells, Jurkat T‐cells and mouse dendritic cells in their buffer solutions have been irradiated with near‐infrared subpicosecond laser pulses in vitro.Results: A window of laser power density, approximately between 1 GW/cm2 and 10 GW/cm2, has been observed that allows killing the viral particles while leaving mammalian cells unharmed.Conclusion: The ultrashort pulsed laser technology may have great potential for disinfection of blood components.

164 DEVELOPMENT OF MURINE EMBRYOS AFTER INJECTION OF UNCOATED GOLD AND SILVER NANOPARTICLES

Novel techniques such as ultrashort pulsed laser technology to produce in situ bio-conjugated nanoparticles (NP) as biomarkers for optical imaging and intervention hold great potential to observe dynamic processes in gametes and embryos without affecting their developmental potential. With regard to toxicology, current preliminary evidence is mainly based on specific cell lines and suggests low toxicity for gold NP (GNP), but a higher toxicity for silver NP (SNP), which also possess a considerable antibacterial effect. Little is known about their impact on sensitive biological systems as early mammalian embryos. The present study investigated the potential toxicity of GNP and SNP in murine embryos for the first time. Since the NP were laser-generated, they formed a stable dispersion in water without the need of surface coating, which might have caused additional toxic effects. Approximately 10 pL of a NP díspersion (average NP diameter of 15 nm) containing 50 μg mL-1 of either GNP or SNP were injected into 1 blastomere of 2-cell-stage embryos (n = 93 or 75, respectively), derived from superovulated NMRI mice. Embryos injected with water alone (n = 79) served as controls. Untreated embryos (n = 92) were run as a handling control. Successful NP injection was confirmed using laser scanning confocal microscopy. After treatment, embryos were cultured for 72 h at 37°C and 5% CO2 in KSOM plus 1% BSA. Embryo development was assessed on a daily basis. No abnormal development was observed. The handling controls reached a blastocyst rate of 77.2%. A total of 66.2% of the water-injected embryos developed to blastocysts, compared to 62.4% and 56.0% after injection of GNP and SNP, respectively. Neither 1-way ANOVA nor an additional chi-square test indicated significant differences between treatment groups. In conclusion, these preliminary data indicate that intracytoplasmatic injection of GNP and SNP had no significant impact on embryo development. Further tests, including qRT-PCR of development-relevant genes in blastocysts and transfer of injected embryos into recipient animals to study potential long-term effects, are underway to gain a better understanding of GNP and SNP embryo toxicology. We gratefully acknowledge the support of the Masterrind GmbH Verden and the NBank Niedersachsen.

Crystal Chemistry Approach in Yb Doped Laser Materials

AbstractFor Abstract see ChemInform Abstract in Full Text.

Crystal Chemistry Approach in Yb Doped Laser Materials

The emergence of new laser crystals has allowed progress in ultrashort-pulsed laser technology and high power lasers. Extensive researches on new Yb3+ doped crystals enable development of all-solid-state femtosecond lasers. Thermo-mechanical properties should be taken into account. The review of the state of the art on the Yb doped laser material for high power and ultrafast pulses generation is presented.