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Spiky Nickel Electrodes for Electrochemical Oxygen Evolution Catalysis by Femtosecond Laser Structuring
摘要： Micro- and nanostructured Ni/NiO surfaces were generated by femtosecond laser structuring for oxygen evolution reaction in alkaline water electrolysis cells. For two different angles between the laser beam and the nickel surface, two different types of laser-structured electrodes were prepared, characterized, and compared with a plane tempered nickel electrode. Their electrochemical activities for the oxygen evolution reaction were tested by using cyclic and linear sweep voltammetry. The chemical surface composition was investigated by X-ray photoelectron spectroscopy. Laser structuring increased the overall electrochemical performance by more than one order of magnitude. The overpotential of the laser-structured electrodes for the oxygen evolution reaction was decreased by more than 100 mV due to high defect densities of the structures created by the laser ablation process.
关键词： nickel electrodes,femtosecond laser structuring,alkaline water electrolysis,electrochemical catalysis,oxygen evolution reaction
更新于2025-09-23 15:21:01
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Ytterbium-doped fibre femtosecond laser offers robust operation with deep and precise microsurgery of C. elegans neurons
摘要： Laser microsurgery is a powerful tool for neurobiology, used to ablate cells and sever neurites in-vivo. We compare a relatively new laser source to two well-established designs. Rare-earth-doped mode-locked fibre lasers that produce high power pulses recently gained popularity for industrial uses. Such systems are manufactured to high standards of robustness and low maintenance requirements typical of solid-state lasers. We demonstrate that an Ytterbium-doped fibre femtosecond laser is comparable in precision to a Ti:Sapphire femtosecond laser (1–2 micrometres), but with added operational reliability. Due to the lower pulse energy required to ablate, it is more precise than a solid-state nanosecond laser. Due to reduced scattering of near infrared light, it can lesion deeper (more than 100 micrometres) in tissue. These advantages are not specific to the model system ablated for our demonstration, namely neurites in the nematode C. elegans, but are applicable to other systems and transparent tissue where a precise micron-resolution dissection is required.
关键词： Ytterbium-doped fibre femtosecond laser,Laser microsurgery,neuronal regeneration,Ti:Sapphire femtosecond laser,solid-state nanosecond laser,C. elegans
更新于2025-09-23 15:19:57
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Simulation of femtosecond interferometry when studying the effect of intense laser irradiation of a transparent medium
摘要： A method for comparing experimental and simulation results obtained when transmitting a femtosecond laser pulse through a material is proposed. This method is based on computer reproduction of photographs recorded using femtosecond interferometry. A numerical analysis of the spatial and temporal evolution of an intense (~1013 W cm–2) pulse propagating in the bulk of yttrium aluminium garnet is presented.
关键词： fast processes in solids,femtosecond interferometry,femtosecond laser radiation
更新于2025-09-23 15:19:57
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Chemical effects during the formation of various types of femtosecond laser-generated surface structures on titanium alloy
摘要： In this contribution, chemical, structural, and mechanical alterations in various types of femtosecond laser-generated surface structures, i.e., laser-induced periodic surface structures (LIPSS, ripples), Grooves, and Spikes on titanium alloy, are characterized by various surface analytical techniques, including X-ray diffraction and glow-discharge optical emission spectroscopy. The formation of oxide layers of the different laser-based structures inherently influences the friction and wear performance as demonstrated in oil-lubricated reciprocating sliding tribological tests (RSTTs) along with subsequent elemental mapping by energy-dispersive X-ray analysis. It is revealed that the fs-laser scan processing (790 nm, 30 fs, 1 kHz) of near-wavelength-sized LIPSS leads to the formation of a graded oxide layer extending a few hundreds of nanometers into depth, consisting mainly of amorphous oxides. Other superficial fs-laser-generated structures such as periodic Grooves and irregular Spikes produced at higher fluences and effective number of pulses per unit area present even thicker graded oxide layers that are also suitable for friction reduction and wear resistance. Ultimately, these femtosecond laser-induced nanostructured surface layers efficiently prevent a direct metal-to-metal contact in the RSTT and may act as an anchor layer for specific wear-reducing additives contained in the used engine oil.
关键词： Tribology,Femtosecond laser processing,GD-OES,Surface chemistry,XRD,LIPSS,Laser-induced periodic surface structures,Laser-induced oxide layer
更新于2025-09-23 15:19:57
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Femtosecond laser-induced non-thermal welding for a single Cu nanowire glucose sensor
摘要： Copper nanowires (CuNWs) are a key building block to facilitate carrier conduction across a broad range of nanodevices. For integration into nanoscale devices, manipulation and welding of these nanowires need to be overcome. Based on high energy density laser processing investigation, we report on innovative welding of single CuNWs to a silver film using a tightly focused laser beam combined with manipulation of CuNWs through the dielectrophoresis (DEP) method. Two types of lasers, femtosecond (FS) and continuous-wave (CW), were employed to analyze, improve, and control Cu-NW melting characteristics under high energy density irradiation. The FS laser welding of CuNWs resulted in a metallic joint with a low contact resistance suitable for functional electronic nanodevices. Computational simulations using the 1-D heat diffusion equation and finite difference method (FDM) were performed to gain an insight into metal–laser interactions for high performance welded contact development. Simulation studies on lasers established contrasting melting behavior of metal under laser irradiation. The device feasibility of CuNW based welded contacts was evaluated in terms of the electrical performance of a glucose sensor. It was possible to sense glucose concentration down to 10?6 M, demonstrating a path towards integration of CuNWs into wearable, flexible nanoelectronic devices.
关键词： glucose sensor,femtosecond laser,Copper nanowires,laser welding,dielectrophoresis,nanoelectronics,continuous-wave laser
更新于2025-09-23 15:19:57
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Zukunftsperspektiven des Femtosekundenlasers in der Vorderabschnittschirurgie; Future perspectives of the femtosecond laser in anterior segment surgery;
摘要： Around 12 years after its introduction laser cataract surgery (LCS) has enabled remarkable progress, such as extremely precise capsulotomy and lens fragmentation with reduced or no ultrasound energy at all (zero phako); however, another innovation push is necessary to bring this technology to its full potential. Among the many benefits that have not yet been fully explored are primary posterior laser capsulotomy (PPLC) and the use of the femtosecond laser in pediatric cataract patients. In the present collective of patients in whom a PPLC was carried out at the end of the operation, a clearly reduced prevalence of secondary cataract could be observed, whereas the short additional intervention was not associated with notable complications. The LCS in infants is best carried out as an off-label procedure, which has been rendered more precise by the Bochum formula. In the near future, postoperative laser fine tuning will enable the target refraction to be achieved in most patients. Laser-induced refractive index change (LIRIC) will enable very exact refraction alterations on an already implanted intraocular lens (IOL), on a contact lens and on a treatment native cornea. A new version of the Scheimpflug camera will be used just prior to surgery to analyze the morphology and kernel density of the lens opacity and to carry out a real-time grading of lens hardness. Based on this categorization, where the system classifies the results into five different density grades, the surgeon is automatically provided with an individualized fragmentation pattern defined preoperatively by the operator. A further innovation of the same system involves microcorneal incisions for fine tuning of residual refractive deficits.
关键词： Femtosecond laser-assisted cataract surgery,Bochum formula,Postoperative refractive enhancement/fine tuning,Primary posterior laser capsulotomy,Laser-induced refractive index change
更新于2025-09-23 15:19:57
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Femtosecond Laser Additive Manufacturing of Multi-Material Layered Structures
摘要： Laser additive manufacturing (LAM) of a multi-material multi-layer structure was investigated using femtosecond fiber lasers. A thin layer of yttria-stabilized zirconia (YSZ) and a Ni–YSZ layer were additively manufactured to form the electrolyte and anode support of a solid oxide fuel cell (SOFC). A lanthanum strontium manganite (LSM) layer was then added to form a basic three layer cell. This single step process eliminates the need for binders and post treatment. Parameters including laser power, scan speed, scan pattern, and hatching space were systematically evaluated to obtain optimal density and porosity. This is the first report to build a complete and functional fuel cell by using the LAM approach.
关键词： femtosecond laser,laser,fuel cell,additive manufacturing,fiber laser,YSZ,SOFC
更新于2025-09-23 15:19:57
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Nanodot array deposition via single shot laser interference pattern using laser-induced forward transfer
摘要： Laser-induced forward transfer (LIFT) is a direct-writing technique capable of depositing a single dot smaller than the laser wavelength at small shot energy through the laser-induced dot transfer (LIDT) technique. To deposit a single nanodot in a single shot of laser irradiation, a liquid nanodrop is transferred from donor to receiver and finally solidified via a solid-liquid-solid (SLS) process. In conventional LIDT experiments, multi-shots with step scanning have been used to form array structures. However, interference laser processing can achieve an arrayed process and generate a periodic structure in a single shot. In this study, a femtosecond laser interference pattern was first applied to LIDT, and an array of nanodots was successfully deposited in a single shot, producing the following unit structures: a single dot, adjoining dots, and stacking dots. The diameter of the smallest nanodot was 355 nm, and the narrowest gap between two adjoining nanodots was 17.2 nm. The LIDT technique produces high-purity, catalyst-free that do not require post-cleaning or alignment processes. Given these significant advantages, LIDT can expand the usability of nanodots in a wide range of fields.
关键词： array,laser-induced dot transfer (LIDT),interference laser processing,nanodot,femtosecond laser,Au,solid-liquid-solid (SLS) mechanism
更新于2025-09-23 15:19:57
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Laser ablation and structuring of CdZnTe with femtosecond laser pulses
摘要： We report an experimental investigation on laser ablation and associated surface structuring of CdZnTe by femtosecond Ti:Sa laser pulses (laser wavelength λ～800 nm, ～35 fs, 10 Hz), in air. By exploiting different static irradiation conditions, the fluence threshold and the incubation effect in CdZnTe are estimated. Interestingly, surface treatment with a low laser fluence (laser pulse energy E～5-10 μJ) and number of shots (5≤ N ≤50) show the formation of well-defined cracks in the central part of the shallow crater, which is likely associated to a different thermal expansion coefficients of Te inclusions and matrix during the sample heating and cooling processes ensuing femtosecond laser irradiation. Irradiation with a larger number of pulses (N～500, 1000) with higher pulse energies (E～30-50 μJ) results in the formation of well-defined laser-induced periodic surface structures (LIPSS) in the outskirts of the main crater, where the local fluence is well below the material ablation threshold. Both low spatial frequency and high spatial frequency LIPSS perpendicular to the laser polarization are found together and separately depending on the irradiation condition. These are ascribed to a process of progressive aggregation of randomly distributed nanoparticles produced during laser ablation of the deep crater in the region of the target irradiated by a fluence below the ablation threshold with many laser pulses.
关键词： Laser ablation,CdZnTe,Femtosecond laser surface processing,Laser induced periodic surface structures
更新于2025-09-23 15:19:57
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - All-Fiber 2.07 μm Distributed Feedback Laser Based on π-Phase-Shifted FBG Inscribed in Heavily Doped Holmium Fiber by Femtosecond Laser Pulses
摘要： Distributed-feedback (DFB) fiber laser is a versatile source of low-noise single-frequency radiation that finds applications in spectroscopy, optical communications and sensing devices. Depending on the active medium, different lasing wavelengths can be obtained: 1.03–1.12 μm for Yb, 1.53–1.62 μm for Er, and 1.73–1.93 μm for Tm-doped fibers. Special fiber Bragg grating (FBG) with a length of 20–70 mm and phase shift in the structure, directly written in an active medium, serves as distributed feedback cavity of this type of laser. Commonly, special UV photosensitive fibers and phase masks inscription technique are used for an FBG fabrication. Alternative femtosecond (fs) point-by-point technique [1] has a number of advantages as compared to UV-based ones: 1) wide variety of active fibers can serve as a host material for an FBG, thanks to the nonlinear mechanism of fs pulses absorption, 2) FBG period can be easily tuned by controlling fs pulses frequency and velocity of fiber translation during the inscription process, 3) each fiber grating “pitch” can be written independently, which means that phase shift with an exact value and position along FBG can be introduced. Despite the number of publications dealing with holmium fiber lasers [2], there no publications devoted to DFB ones. At the same time, such type of laser sources has a great potential as a master oscillator in all-fiber coherent beam combination systems [3]. We report on the creation of holmium-doped DFB fiber laser with a wavelength of 2.07 μm operating in single-frequency regime (Fig. 1a). The laser is based on custom-made single-mode holmium-doped fiber having absorption coefficient about 43 dB/m at 1.125 μm, which is the wavelength of pump Yb fiber laser. 42-mm π-phase-shifted FBG was directly inscribed in the active fiber by femtosecond IR laser pulses and served as distributed feedback cavity of the laser. Lasing threshold was reached at 350 mW pump power, and output power exceeded 36 mW at pump power of 4.8 W (Fig. 1b). Single-polarization mode operation was observed with linewidth of ~10 kHz. Additionally to the room-temperature operation regime we will present and discuss the laser operation regimes at cryogenic temperature (77 K), as well as high-temperature (>400 K). To the best of our knowledge, it is the first realization of all-fiber DFB laser based on holmium active medium.
关键词： femtosecond laser pulses,holmium-doped fiber,single-frequency radiation,Distributed-feedback fiber laser,π-phase-shifted FBG
更新于2025-09-23 15:19:57