Search Results (330)

The effect of Mn-doped zinc ferrite nanoparticles at a low volume concentration (1 × 10⁻⁴) on structural changes in the nematic liquid crystals 6CHBT and 5CB, induced by weak magnetic fields, was investigated using surface acoustic wave (SAW) and light transmission (LT) techniques. Structural changes caused by the applied magnetic field, in both increasing and decreasing modes, as well as after pulsed changes, were examined by measuring the responses of SAW attenuation and LT using a linearly polarized laser beam. The influence of nanoparticle shape (rods, needles, and clusters) and temperature on the structural changes was investigated. A shift in the threshold field and the transition temperature was observed. In addition, the magnetic properties of the individual samples in powder form were examined using M–H curves, M–T curves, and XRD patterns. The results obtained from all measurements are compared, and the effectiveness of each technique, considering the influence of nanoparticle shape and suspension stability, was evaluated. Full article

We experimentally demonstrate an 80 Gbit/s Nyquist-dense wavelength division multiplexed (Nyquist-DWDM) transmission system operating in a simulated atmospheric turbulence channel. The system utilizes eight wavelength-tunable lasers with 100 GHz spacing, modulated by cascaded Mach–Zehnder modulators, to generate phase-locked Nyquist pulse sequences with a 10 GHz repetition rate and a temporal width of 66.7 ps. Each channel is synchronously modulated with a 10 Gbit/s pseudo-random bit sequence (PRBS) and transmitted through controlled weak turbulence conditions generated by a temperature-gradient convection chamber. Experimental measurements reveal that, as the turbulence intensity increases from $C_n^2=1.01\times {10}^{-16}$ to $5.71\times {10}^{-16} {\mathrm{m}}^{-2/3}$, the signal-to-noise ratio (SNR) of the edge channel (C29) and central channel (C33) decreases by approximately 6.5 dB while maintaining stable Nyquist waveform profiles and inter-channel orthogonality. At a forward-error-correction (FEC) threshold of $3.8\times {10}^{-3}$, the minimum receiver sensitivity is −17.66 dBm, corresponding to power penalties below 5 dB relative to the back-to-back condition. The consistent SNR difference (<2 dB) between adjacent channels confirms uniform power distribution and low inter-channel crosstalk under turbulence. These findings verify that Nyquist pulse shaping substantially mitigates phase distortion and scintillation effects, demonstrating the feasibility of high-capacity DWDM free-space optical (FSO) systems with enhanced spectral efficiency and turbulence resilience. The proposed configuration provides a scalable foundation for future multi-wavelength FSO links and hybrid fiber-wireless optical networks. Full article

We experimentally and through simulations demonstrate a passively mode-locked fiber laser based on nonlinear polarization rotation, which generates the evolution from h-shaped pulses to GHz harmonic trains. When the polarization angle is continuously changed, the h-shaped pulse sequentially evolves into multiple pulses, bunched solitons, and harmonic pulses. The maximum order of harmonic trains obtained in experiments is 120, corresponding to the repetition frequency of 1.03996 GHz. The coupled Ginzburg-Landau equation and two-time-scale approach to gain is provided to characterize the laser physics. The fast and slow evolution of gain contributes to the stabilization and length of one soliton pattern, respectively. The proposed fiber laser is cost effective and easy to implement, providing a potential way to study soliton dynamics in depth. Full article

Pulsed liquid-based nanoparticle synthesis has emerged as a versatile and environmentally friendly approach for producing a wide range of nanomaterials with tunable properties. Unlike conventional chemical methods, pulsed techniques—such as pulsed laser ablation in liquids (PLAL), electrical discharge, and other energy-pulsing methods—enable the synthesis of high-purity nanoparticles without the need for toxic precursors or stabilizing agents. This review provides a comprehensive overview of the fundamental mechanisms driving nanoparticle formation under pulsed conditions, including plasma–liquid interactions, cavitation, and shockwave dynamics. We discuss the influence of key synthesis parameters, explore different pulsed energy sources, and highlight the resulting effects on nanoparticle size, shape, and composition. The review also surveys a broad spectrum of material systems and outlines advanced characterization techniques for analyzing synthesized nanostructures. Furthermore, we examine current and emerging applications in biomedicine, catalysis, sensing, energy, and environmental remediation. Finally, we address critical challenges such as scalability, reproducibility, and mechanistic complexity, and propose future directions for advancing the field through hybrid synthesis strategies, real-time diagnostics, and machine learning integration. By bridging mechanistic insights with practical applications, this review aims to guide researchers toward more controlled, sustainable, and innovative nanoparticle synthesis approaches. Full article

Ytterbium-doped femtosecond fiber lasers are widely used in scientific research, industrial processing, and other fields due to their high quantum efficiency, wide gain bandwidth, and compact structure. This article addresses the problems of low processing efficiency and difficulty in increasing the average power of femtosecond lasers. A high repetition rate fiber chirped pulse amplification system is built, which uses a high repetition rate Figure-9 fiber laser as the seed source and an acousto-optic modulator (AOM) to shape the dense pulse train in the time domain. The main amplification stage uses a large mode field ytterbium-doped fiber to achieve full fiberization of the amplification system, and a volume grating (VBG) is selected as the pulse compressor to make the laser system highly integrated. When the repetition rate is 67.5 MHz, the compressed output laser has an average power of 20.5 W, a pulse width of 447 fs, a pulse train energy of 750 μJ, a spot ellipticity of 0.96, and a beam quality M² better than 1.4 ($M_x^2=1.33$, $M_y^2=1.16$). Full article

The key to proper implant integration in bone replacement is to orchestrate the complex interactions between materials and tissues. Moreover, due to the rapid demographic shift towards aging societies and the increase in elderly and osteoporotic patients, it is of great importance that implant materials are osteointegrative in not only healthy but also compromised bone tissues. Here, titanium (Ti) scaffolds were subjected to shifted laser surface texturing (sLST) using a nanosecond pulsed laser to create an open pore macrotopography with micro-and nano-Ti droplets. In contrast to conventional laser texturing, which leads to high heat accumulation; in sLST, the frequency of laser pulses is low, allowing for resolidification, thereby creating a surface with abundant coverage micro-/nanodroplets. The main objective was to compare the cellular responses of human mesenchymal stromal cells (hMSCs) on sLST-textured Ti surfaces (LT-Ti) for the first time with standard sand-blasted, acid-etched surfaces (SLA-Ti). In-depth analyses of cell survival, proliferation, shape, mineralization, and gene expression were performed. Cell survival/proliferation was found to be similar on both surfaces; however, SEM imaging revealed differences in hMSC morphology. On LT-Ti, cells adopted well-rounded shapes, whereas on SLA-Ti they assumed more planar shapes. Bulk RNA sequencing performed after short-term culture on both surfaces disclosed expression changes in genes such as DUSP6, TNFSF12-TNFSF13 and SULT1A4. Remarkably, the osteogenic differentiation capacity of hMSCs was significantly enhanced on LT-Ti compared to SLA-Ti. Furthermore, aged/osteoporotic donor cohorts showed significantly enhanced matrix mineralization on LT-Ti. In conclusion, our novel results demonstrate that sLST-Ti surfaces are safe, highly biocompatible, can rescue patient-cohort-specific mineralization behavior, and therefore hold great potential for the development into next-generation implants, which are suitable for both the elderly and bone-compromised populations. Full article

A glow discharge polymer (GDP) has unique physical properties—transparency, brittleness, and hardness—that pose challenges for traditional mechanical machining techniques. We have investigated the microhole fabrication of GDP films using shaped femtosecond laser pulses to study the influence of pulse shape, delay between subpulses, and focusing position on processing precision and efficiency. By precisely controlling pulse characteristics, such as duration, energy, and subpulse intervals, the efficiency, hole morphology, and processing quality were significantly improved. The experimental results demonstrated that femtosecond lasers with subpulses produce smaller and more uniform microholes compared to transform-limited pulses. Furthermore, both the pulse shape and focusing position of the laser were found to further influence ablation efficiency. This study establishes, for the first time, the critical role of temporal pulse shaping in optimizing the femtosecond laser drilling of GDP films, which provides valuable information on optimizing femtosecond laser parameters for precision processing of polymer films and advances the potential for microhole fabrication in industrial applications. Full article

This study examines the soliton dynamics in the time-fractional cubic–quintic nonlinear non-paraxial propagation model, applicable to optical signal processing, nonlinear optics, fiber-optic communication, and biomedical laser–tissue interactions. The fractional framework exhibits a wide range of nonlinear effects, such as self-phase modulation, wave mixing, and self-focusing, arising from the balance between cubic and quintic nonlinearities. By employing the Multivariate Generalized Exponential Rational Integral Function (MGERIF) method, we derive an extensive catalog of analytic solutions, multi-peakon structures, lump solitons, kinks, and bright and dark solitary waves, while periodic and singular solutions emerge as special cases. These outcomes are systematically constructed within a single framework and visualized through 2D, 3D, and contour plots under both anomalous and normal dispersion regimes. The analysis also addresses modulation instability (MI), interpreted as a sideband amplification of continuous-wave backgrounds that generates pulse trains and breather-type structures. Our results demonstrate that cubic–quintic contributions substantially affect MI gain spectrum, broadening instability bands and permitting MI beyond the anomalous-dispersion regime. These findings directly connect the obtained solution classes to experimentally observed routes for solitary wave shaping, pulse propagation, and instability and instability-driven waveform formation in optical communication devices, photonic platforms, and laser technologies. Full article

Although laser cavitation was discovered half a century ago, novel geometries and regimes to excite this effect have been vigorously explored during the past few decades. This research is driven by a variety of applications of laser cavitation in demanding branches of science and technology, such as microfabrication, synthesis of nanoparticles, manipulation of cells, surgery, and lithotripsy. In this work, we combine experimental studies using high-repetition-rate imaging and numerical simulations to uncover a novel regime of the laser cavitation observed upon excitation of a liquid by a train of laser pulses with the pulse energy of 140 mJ and duration of 1.2 μs delivered through a quartz optical fiber. Once the lifetime of the initial cavitation bubble (excited by the first laser pulse) is larger than the period between pulses, which is 34.3 μs, the secondary pulses in the train pass the gas in a bubble and evaporate additional liquid. This results in the formation of a cascaded cavitation bubble of larger volume and elongated shape of $4.6$ mm length compared to $3.8$ mm in case of excitation by a single laser pulse. In addition, the results of acoustic measurements confirm the presence of shock waves in the applied liquid. Finally, potential applications of the uncovered laser cavitation regime are discussed. Full article

For exploration of space, in particular in attempts to find new extra-terrestrial resources, human society has encountered the problem of space pollution with human-made debris, which represents high risks for space missions. This prompted extensive activities for cleaning the space using various techniques, which are briefly overviewed here. But the main focus of this paper is on using lasers for space debris removal. The attention is drawn to laser beam shaping techniques, which are discussed as potential technologies for deorbiting space debris, providing more energetically favorable laser propulsion compared to conventional laser beams. Full article

This study investigates two-sided pulsed-periodic laser welding of three-layer metal–polymer–metal (MPM) composite sheets composed of galvanized dual-phase steel (DPK 30/50+ZE) as outer layers and a polypropylene–polyethylene (PP–PE) core. Welding was performed using a Rofin StarWeld Performance pulsed Nd:YAG laser with controlled parameters: pulse energy (30–32 J), duration (6–8 ms), and frequency (up to 1 Hz). High-quality welds were achieved with penetration depths reaching 70% of the outer metal layer thickness and minimal defects. Microscopic analysis revealed distinct fusion and heat-affected zones (HAZ) with no evidence of cracks or porosity, indicating stable thermal conditions. Mechanical testing showed that the welded joints attained a tensile strength of approximately 470 MPa, about 80% of the ultimate tensile strength of the base metal, with an average elongation of 0.6 mm. These results confirm the structural integrity of the joints. The observed weld morphology and microstructural features suggest that thermal conditions during welding significantly affect joint quality and HAZ formation. The study demonstrates that strong, defect-free joints can be produced using basic beam-shaping optics and outlines a pathway for further improvement through the integration of diffractive optical elements (DOEs) to enhance spatial-energy control in multilayer structures. Full article

In recent years, the generation of circularly polarized attosecond pulses has garnered significant attention due to their potential applications in ultrafast spectroscopy and, notably, in chiral-sensitive molecular detection. The traditional methods for generating such pulses often involve complex laser configurations or specially engineered targets, limiting their experimental feasibility. In this study, we present a streamlined and effective approach to producing circularly polarized attosecond pulses by employing a linearly polarized laser field in conjunction with a stereosymmetric linear molecule, 1-butyne (C₄H₆). The generation of high-order harmonics by this molecular system reveals a distinct plateau in the perpendicular polarization component, which facilitates the generation of isolated attosecond pulses with circular polarization. Through a detailed analysis of the time-dependent charge density dynamics across atomic sites, we identify the atoms primarily responsible for the emission of circularly polarized harmonics in the plane orthogonal to the driving field. Moreover, we explore the role of multi-orbital contributions in shaping the polarization properties of the harmonic spectra. Our findings underscore the importance of molecular symmetry and the electronic structure in tailoring the harmonic polarization, and they demonstrate a viable pathway for using circularly polarized attosecond pulses to probe molecular chirality. This method offers a balance between simplicity and performance, opening new avenues for practical applications in chiral recognition and ultrafast stereochemical analysis. Full article

Monitoring of laser-based processes is essential for ensuring the quality of produced surface structures and for maintaining the process stability and reproducibility. Optical methods based on scatterometry are attractive for industrial monitoring as they are fast, non-contact, non-destructive, and can resolve features down to the sub-microscale. Here, Laser-Induced Periodic Surface Structures (LIPSS) are produced on stainless steel using ultrashort laser pulses in combination with a polygon scanning system. After the process, the fabricated LIPSS features are characterized by microscopy methods and with an optical setup based on scatterometry. Images of the diffraction patterns are collected and the intensity distribution analyzed and compared to the microscopy results in order to estimate the LIPSS height, spatial period, and regularity. The resulting analysis allows us to study LIPSS formation development, even when its characteristic diffraction pattern gradually changes from a double-sickle shape to a diffuse cloud. The scatterometry setup could be used to infer LIPSS height up to 420 nm, with an estimated average error of 7.7% for the highest structures and 11.4% in the whole working range. Periods estimation presents an average error of ~5% in the range where LIPSS are well-defined. In addition, the opening angle of the LIPSS was monitored and compared with regularity measurements, indicating that angles exceeding a certain threshold correspond to surfaces where sub-structures dominate over LIPSS. Full article

The transition to high-energy-density lithium metal batteries (LMBs) is essential for advancing electric vehicle (EV) technologies beyond the limitations of conventional lithium-ion batteries. A key challenge in scaling LMB production is the precise, contamination-free separation of lithium metal (LiM) anodes, hindered by lithium’s strong adhesion to mechanical cutting tools. This study investigates high-speed, contactless laser cutting as a scalable alternative for shaping double-coated LiM anodes. The effects of pulse duration, pulse energy, repetition frequency, and scanning speed were systematically evaluated using a nanosecond pulsed laser system on 30 µm LiM foils laminated on both sides of an 8 µm copper current collector. A maximum single-pass cutting speed of 3.0 m/s was achieved at a line energy of 0.06667 J/mm, with successful kerf formation requiring both a minimum pulse energy (>0.4 mJ) and peak power (>2.4 kW). Cut edge analysis showed that shorter pulse durations (72 ns) significantly reduced kerf width, the heat-affected zone (HAZ), and bulge height, indicating a shift to vapor-dominated ablation, though with increased spatter due to recoil pressure. Optimal edge quality was achieved with moderate pulse durations (261–508 ns), balancing energy delivery and thermal control. These findings define critical laser parameter thresholds and process windows for the high-speed, high-fidelity cutting of double-coated LiM battery anodes, supporting the industrial adoption of nanosecond laser systems in scalable LMB electrode manufacturing. Full article

We present a comprehensive study on the femtosecond laser direct welding of glass and metal, focusing on optimizing processing parameters and understanding the influence of material properties and beam shaping on welding quality. Using microscopy, we identified optimal pulse energy, focal position, and line-spacing for achieving high-quality welds. We further investigated the effects of laser beam shaping and material property differences in various glass-to-metal pairs, including borosilicate, fused silica, and Zerodur glasses welded with mirror-polished metals such as Cu, Mo, Al, Ti, and AISI316 steel. Our results show that Ti and AISI316 steel exhibit the lowest adhesion to borosilicate and fused silica glasses, while Zerodur glass achieves good adhesion with all tested metals. To understand the weldability differences among material pairs, we employed a time-dependent finite-element method to analyze the laser heating-induced thermal stress. Our findings indicate that the welding quality is significantly influenced by the choice of materials and beam shaping, with the vortex beam showing potential for improved welding outcomes. This study provides valuable insights for optimizing glass-to-metal welding processes for various industrial applications. Full article