Single Laser Research Articles

Optimization of SD-3 Nickel-Based Alloy Coating by Single Channel Laser Cladding Using Orthogonal Experimental Method

Optimization of SD-3 Nickel-Based Alloy Coating by Single Channel Laser Cladding Using Orthogonal Experimental Method

Room-temperature sub-100 nm Néel-type skyrmions in non-stoichiometric van der Waals ferromagnet Fe3-xGaTe2 with ultrafast laser writability

Realizing room-temperature magnetic skyrmions in two-dimensional van der Waals ferromagnets offers unparalleled prospects for future spintronic applications. However, due to the intrinsic spin fluctuations that suppress atomic long-range magnetic order and the inherent inversion crystal symmetry that excludes the presence of the Dzyaloshinskii-Moriya interaction, achieving room-temperature skyrmions in 2D magnets remains a formidable challenge. In this study, we target room-temperature 2D magnet Fe3GaTe2 and unveil that the introduction of iron-deficient into this compound enables spatial inversion symmetry breaking, thus inducing a significant Dzyaloshinskii-Moriya interaction that brings about room-temperature Néel-type skyrmions with unprecedentedly small size. To further enhance the practical applications of this finding, we employ a homemade in-situ optical Lorentz transmission electron microscopy to demonstrate ultrafast writing of skyrmions in Fe3-xGaTe2 using a single femtosecond laser pulse. Our results manifest the Fe3-xGaTe2 as a promising building block for realizing skyrmion-based magneto-optical functionalities.

Indirect confirmation and theoretical application of plasma shock−cavitation principle of pulsed laser shock

The coupling strengthening principle of the double physical effect of plasma shock−cavitation was proposed, and the rationality of the cavitation effect in pulsed laser shock treatment under liquid−confined conditions needs to be confirmed urgently. The XRD testing method and 304 stainless steel, which is easy to obtain diffraction peaks, were selected to quantitatively detect and characterize the residual stress distribution in the action area of a single pulse laser beam. The test results and literature analysis show that the different process conditions of laser shock processing bring about different strength matching of the two stress effects of plasma shock and cavitation, and the main source of stress effect of femtosecond laser shock without coating is the cavitation effect. The actual effects of the laser pulse width and other process parameters such as the absorption layer and the constraint layer affect or determine the material modification principle of the pulsed laser surface treatment.

Efficient muon acceleration in laser wakefields driven by single or combined laser pulses

Laser plasma wakefields can provide extremely high fields both in transverse and longitudinal directions, which are very suitable for short-lived charged particle acceleration, such as muons. To get efficient capture and acceleration, we have numerically investigated the acceleration of externally injected muons in laser wakefields driven by usual Gaussian or flying focus lasers. The muons are produced from high-energy electrons interacting with high-Z solid targets, which typically have a broad energy spectrum ranging from hundreds of MeV to several GeV. We classify these muons into three categories according to their initial energies and suggest different drivers for the wakefield acceleration. For low-energy muons (such as E0∼ 600 MeV), as their velocity is much smaller than the phase velocity of a typical wakefield, the optimal driver laser is the combination of a Gaussian laser with a flying focus laser. For moderate-energy muons (such as E0∼ 1.5 GeV), using a Gaussian laser as the driver is the best choice due to its ability to achieve phase-locked acceleration. For high-energy muons (such as E0∼ 5 GeV), in order to avoid dephasing, which usually happens in LWFA, the flying focus laser is suggested to realize phase-locked acceleration. The final muon energies obtained in three cases are 1.2, 2.6, and 6.0 GeV, respectively, with trapping efficiencies of 88%, 92%, and 86%, and the relative energy spread of 2%, 13%, and 10%. Our study demonstrates the possibility for efficient muon acceleration by all optical acceleration with hundred terawatt-class lasers.

3D atomic structure from a single X-ray free electron laser pulse

X-ray Free Electron Lasers (XFEL) are cutting-edge pulsed x-ray sources, whose extraordinary pulse parameters promise to unlock unique applications. Several new methods have been developed at XFELs; however, no methods are known, which allow ab initio atomic level structure determination using only a single XFEL pulse. Here, we present experimental results, demonstrating the determination of the 3D atomic structure from data obtained during a single 25 fs XFEL pulse. Parallel measurement of hundreds of Bragg reflections was done by collecting Kossel line patterns of GaAs and GaP. To the best of our knowledge with these measurements, we reached the ultimate temporal limit of the x-ray structure solution possible today. These measurements open the way for obtaining crystalline structures during non-repeatable fast processes, such as structural transformations. For example, the atomic structure of matter at extremely non-ambient conditions or transient structures formed in irreversible physical, chemical, or biological processes may be captured in a single shot measurement during the transformation. It would also facilitate time resolved pump-probe structural studies making them significantly shorter than traditional serial crystallography.

Simultaneous Application of Raman and Laser-Induced Breakdown Spectroscopy in the Gas Phase with a Single Laser and Detector.

Raman spectroscopy and laser-induced breakdown spectroscopy (LIBS) are powerful tools for molecular and elemental analysis, respectively. Their combined application, however, is challenging due to the differences in the signal generation and detection characteristics. This note proposes three experimental schemes for the simultaneous application of Raman and LIBS for gas-phase diagnostics. Ring-cavity optical pulse stretchers facilitate shaping suitable pulse pairs from a Q-switched laser that enables the quasi-simultaneous detection of the Raman and LIBS signals on a single detector.

Unveiling out-of-loop attosecond timing jitter precision in Ti:sapphire mode-locked lasers with an optical heterodyne technique.

The out-of-loop timing jitter exhibited in free-running Ti:sapphire mode-locked lasers with attosecond resolution is demonstrated using an optical heterodyne technique. To assess the feasibility of the experiment and discrimination signal properties, numerical simulations were conducted for Ti:sapphire mode-locked lasers. For accurately characterizing the genuine phase noise exhibited by Ti:sapphire mode-locked lasers, out-of-loop measurements were conducted, and a straightforward yet improved optical heterodyne setup was employed, allowing simultaneous low-bandwidth locking and out-of-loop timing jitter measurements with two Ti:sapphire mode-locked lasers. The out-of-loop phase noise floor for a single mode-locked laser reaches -203.47 d B c/H z, assuming a 10 GHz carrier frequency. Additionally, the out-of-loop integrated timing jitter is 11.9 a s from 10 kHz to the Nyquist frequency (50 M H z).

Three-Dimensional Manipulation of Micromodules Using Twin Optothermally Actuated Bubble Robots.

A 3D manipulation technique based on two optothermally generated and actuated surface-bubble robots is proposed. A single laser beam can be divided into two parallel beams and used for the generation and motion control of twin bubbles. The movement and spacing control of the lasers and bubbles can be varied directly and rapidly. Both 2D and 3D operations of micromodules were carried out successfully using twin bubble robots. The cooperative manipulation of twin bubble robots is superior to that of a single robot in terms of stability, speed, and efficiency. The operational technique proposed in this study is expected to play an important role in tissue engineering, drug screening, and other fields.

Tunable single frequency Hz-magnitude narrow linewidth Brillouin fiber laser based on parity-time symmetry.

An Hz-magnitude ultra-narrow linewidth single-frequency Brillouin fiber laser (BFL) is proposed and experimentally demonstrated. The single frequency of the laser is selected by parity-time (PT) symmetry, which consists of a stimulated Brillouin scatter (SBS) gain path excited by a 24 km single-mode fiber (SMF) and an approximately equal length loss path tuned with a variable optical attenuator (VOA). These paths are coupled through a fiber Bragg grating (FBG) into a wavelength space. Accomplishing single-frequency oscillation involves the precise adjustment of polarization control (PC) and VOA to attain the PT broken phase. In the experiment, the linewidth of the proposed BFL is 9.58 Hz. The optical signal-to-noise ratio (OSNR) reached 78.89 dB, with wavelength and power fluctuations of less than 1pm and 0.02 dB within one hour. Furthermore, the wavelength can be tuned from 1549.9321 nm to 1550.2575 nm, with a linewidth fluctuation of 1.81 Hz. The relative intensity noise (RIN) is below -74 dB/Hz. The proposed ultra-narrow single-frequency BFL offers advantages such as cost-effectiveness, ease of control, high stability and excellent output characteristics, making it highly promising for the applications in the coherent detection.

Spectral control of beyond extreme ultraviolet emission from a dual-laser-produced plasma

We demonstrated spectral control of beyond extreme ultraviolet (B-EUV) emission at a central wavelength of 6.76 nm from a gadolinium (Gd) laser-produced plasma. The highest spectral purity (SP) was 5.1% under dual 1-μm laser pulse irradiation. It doubled compared to a value of 2.4% attained under single laser pulse irradiation of solid density Gd because of the reduction in optical depth. The highest maximum SP was higher than that obtained using a mid-infrared laser at 10.6 μm. The SP for the 150-ps main laser was also higher than that for 6-ns main laser irradiation. Our approach can be extended to mid-infrared solid-state laser-produced plasmas (LPPs) using driving laser wavelengths ranging from 2 to 9 μm for efficient B-EUV source development.

Blinking characteristics of organic fluorophores for blink-based multiplexing

Single-molecule fluorescence experiments have transformed our understanding of complex materials and biological systems. Whether single molecules are used to report on their nano-environment or provide for localization, understanding their blinking dynamics (i.e., stochastic fluctuations in emission intensity under continuous illumination) is paramount. We recently demonstrated another use for blinking dynamics called blink-based multiplexing (BBM), where individual emitters are classified using a single excitation laser based on blinking dynamics, rather than color. This study elucidates the structure-activity relationships governing BBM performance in a series of model rhodamine, BODIPY, and anthraquinone fluorophores that undergo different photo-physical and-chemical processes during blinking. Change point detection and multinomial logistic regression analyses show that BBM can leverage spectral fluctuations, electron and proton transfer kinetics, as well as photostability for molecular classification—even within the context of a shared blinking mechanism. In doing so, we demonstrate two- and three-color BBM with ≥ 93% accuracy using spectrally-overlapped fluorophores.

How much energy do we need to ablate 1 cubic millimeter of stone during Thulium Fiber Laser lithotripsy? An in vitro study.

Both Holmium:yttrium-aluminium-garnet (Ho:YAG) laser and Thulium Fiber Laser (TFL) can effectively treat all urinary stone types. This in vitro study evaluated the ablation volume per pulse (AVP) and required energy needed to ablate 1mm3 (RE, J/mm3) of various stone types at different laser settings with TFL. 272-µm core-diameter laser fibers (Boston Scientific©) were connected to a 50Watts TFL generator (IPG®). An experimental setup immerged human stones of calcium oxalate monohydrate (COM), uric acid (UA), and cystine (CYS) with a single pulse lasing emission (0.5/0.8/1J), in contact mode. Stones were dried out before three-dimensional scanning to measure AVP and deduce from the pulse energy (PE) and AVP the RE. A direct comparison with known Ho:YAG's AVP and RE was then carried out. AVP for COM stones was significantly greater than those for CYS stones and similar to UA stones (p = 0.02 and p = 0.06, respectively). If AVP increased with PE against COM and UA stones, AVP decreased against CYS stones. 1J PE resulted in a threefold lower RE compared with other PE for COM stones. On the contrary, RE for CYS increased with PE, whereas PE did not had influence on RE for UA. TFL was associated with greater AVP for COM, but lower for UA and CYS stones compared to Ho:YAG laser. This in vitro study firstly describes the ablation volume per pulse and required energy to treat a cubic millimeter of three frequent human stone types, and suggest TFL could not be suited for cystine. Therefore, stone composition could be considered when choosing the laser source for lithotripsy.

Temperature-controlled spectral tuning of a single wavelength polymer-based solid-state random laser.

We demonstrate temperature-controlled spectral tunability of a partially-pumped single-wavelength random laser in a solid-state random laser based on DCM [4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran] doped PMMA (polymethyl methacrylate) dye. By carefully shaping the spatial profile of the pump, we first achieve a low-threshold, single-mode random lasing with an excellent side lobe rejection. Notably, we show how temperature-induced changes in the refractive index of the PMMA-DCM layer result in a blue shift of this single lasing mode. We demonstrate spectral tunability over an 8nm-wide bandwidth.

Ultrafast and persistent photoinduced phase transition at room temperature monitored by streaming powder diffraction

Ultrafast photoinduced phase transitions at room temperature, driven by a single laser shot and persisting long after stimuli, represent emerging routes for ultrafast control over materials’ properties. Time-resolved studies provide fundamental mechanistic insight into far-from-equilibrium electronic and structural dynamics. Here we study the photoinduced phase transformation of the Rb0.94Mn0.94Co0.06[Fe(CN)6]0.98 material, designed to exhibit a 75 K wide thermal hysteresis around room temperature between MnIIIFeII tetragonal and MnIIFeIII cubic phases. We developed a specific powder sample streaming technique to monitor by ultrafast X-ray diffraction the structural and symmetry changes. We show that the photoinduced polarons expand the lattice, while the tetragonal-to-cubic photoinduced phase transition occurs within 100 ps above threshold fluence. These results are rationalized within the framework of the Landau theory of phase transition as an elastically-driven and cooperative process. We foresee broad applications of the streaming powder technique to study non-reversible and ultrafast dynamics.

Multi-laser powder bed fusion of Ti6Al4V: Diode area melting utilizing low-power 450 nm diode lasers

Diode Area Melting (DAM) is an innovative approach to laser powder bed fusion. This research for the first time utilized multiple low wavelength (450 nm) and low power lasers (4 W each) to simultaneously process Ti6Al4V from a powder bed, resulting in high density samples (> 99%). The use of nine lasers perpendicular to the scanning direction allowed for the creation of melt pools with widths larger than 1000 µm, reducing the number of passes within a layer compared to traditional single laser LPBF systems. However, the increase in melt pool width creates challenges related to maintaining uniform melt pool penetration depths, this intern creates issues achieving high density in multi-layer parts. A parameter map based on normalized energy density was created. The research also investigated the effect of variable process conditions (scanning speed, hatch distance, and layer height), normalized energy density on densification, microstructure, and hardness. Implementing a rescanning strategy on each layer reduced average surface roughness and increased density while reducing hardness by approximately 40%. X-ray Diffraction analyses showed that the β phase occurred with increased energy density in as-built samples. Coarser lamellar structures were observed in the lower sections due to slower cooling rates, while finer, more martensite structures were observed towards the top, resulting in a basket-weave type microstructure throughout the sample. Furthermore, the lamellar sub-grains were visible without etching. This innovative technology shows that an array of low-power lasers can melt and fuse Ti6Al4V powder to create dense samples.

A Superhydrophobic Surface on a Superalloy Substrate with Properties of High Mechanical Strength and Self-Cleaning of Carbon Deposition.

Laser processing is an efficient method for fabricating a superhydrophobic surface and has attracted much attention due to its multifunctionality. However, excessive laser processing, such as laser beam overlap and multiple scans, generates both a thick, brittle recast layer and a thin material thickness, thereby greatly reducing the mechanical strength of the substrate. In addition, there is no report on fabricating a superhydrophobic surface on a superalloy substrate whose application includes a self-cleaning property. This work proposes the fabrication of a superhydrophobic surface on a superalloy substrate with high mechanical strength by optimizing the laser processing parameters including laser power, scanning speed, line spacing, and number of scans. We found that the microstructures required by superhydrophobicity could be constructed with a single laser scan. which could guarantee a minimal loss of the mechanical strength. The fabricated superhydrophobic surface on the superalloy substrate exhibited excellent self-cleaning of carbon deposition, showing good application potential in the aero engine field.

Experimental Investigation of Actively Q-Switched Dy3+ Doped Fluoride Single Mode Fiber Laser Operating Near 3 μm

Experimental Investigation of Actively Q-Switched Dy³⁺ Doped Fluoride Single Mode Fiber Laser Operating Near 3 μm

Tumor fluorescence and oxygenation monitoring during photodynamic therapy with chlorin e6 photosensitizer

BackgroundThe study is aimed at developing a method for monitoring photodynamic therapy (PDT) of a tumor using chlorin-type photosensitizers (PSs). Lack of monitoring of chlorin e6 (Cе6) photobleaching, hemoglobin oxygenation and blood flow during light exposure can limit the PDT effectiveness. Materials and methodsPhototheranostics includes spectral-fluorescence diagnostics of Ce6 distribution in the NIR range and PDT with simultaneous assessment of hemoglobin oxygenation and tumor blood flow. Fluorescence diagnostics and PDT were performed using the single laser λexc=660 ± 5 nm. ResultsCombined spectroscopic PDT monitoring method allowed simultaneous estimation of Ce6 photobleaching, hemoglobin oxygenation and tumor vascular thrombosis during PDT without interrupting the therapeutic light exposure. ConclusionThe developed method of tumor phototheranostics using chlorin-type PSs may make it possible to personalize the duration of therapeutic light exposure during PDT.

From toggle to precessional single laser pulse switching

With the advent of nanotechnologies, it has been possible to extend the number of stimuli that can be used to control the state of a magnetic nanostructure. Among those stimuli, single laser pulse excitation allows, under certain conditions, to obtain energy-efficient ultrafast magnetization reversal. With this respect, two different types of single pulse switching mechanisms have been reported. The first one consists in a sub-picosecond ultrafast toggle switching, which was observed mainly in Gd based alloys. The second type relies on sub-nanosecond precessional switching occurring in rare earth–transition metal alloys/multilayers. Here, we demonstrate that single pulse all optical switching is achieved in Co68Tb32/Co100−xGdx/Co68Tb32 trilayers in which the behavior can be tuned from toggle to precessional by changing the composition of the Co100−xGdx alloy.

Laser fabrication of epidermal paper-based graphene sensors

There is an increasing demand for epidermal sensors that can adapt to the contours and the movements of the human body, but the fabrication of prevalent polymer-based epidermal sensors often involves costly materials and complex procedures. Paper has emerged as a cost-effective substrate for next-generation epidermal sensors, featuring such advantages as bendability, breathability, biocompatibility, and environment-friendliness. However, transducing materials are commonly introduced to paper substrates in post hoc manners or through time-consuming syntheses, in addition to the direct manufacturing of paper. Here we report an integrative method to fabricate epidermal paper-based graphene sensors, where graphene induction and paper cutting can be achieved in a single lasing procedure to generate both transducing components and overall sensor formats. Lasing conditions are systematically explored, mainly to control the multifaceted properties of the obtained graphene transducers. The resultant paper-based graphene structures exhibit sufficient reliability in various scenarios regarding storage, lighting, and deformation. Paper-based graphene sensors are strategically designed in terms of overall formats, geometric patterns, hydrophilicity/hydrophobicity, surface functionalization, and readouts for measuring biophysical and biochemical information relevant to human health. The sensor performance can be optimized by adjusting laser power, and the calibrated sensitivities for mechanical strain, temperature, humidity, pH, and glucose are 76.93, –0.15% °C–1, 37.06 μA %–1, 28.13 mV pH–1, and 1.26 μA mM–1, respectively. Multimodal health monitoring is demonstrated with paper-based graphene sensors. Our approach can facilitate the generation of epidermal paper-based sensors and meet diverse requirements of health monitoring.