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Synthesis of silicon carbide nanocrystals and multilayer graphitic carbon by femtosecond laser irradiation of polydimethylsiloxane
摘要： Laser-based modification of polymer materials has been emerging as a versatile and efficient technique to simultaneously form and pattern electrically conductive materials. Recently, it has been revealed that native polydimethylsiloxane (PDMS) can be modified into electrically conductive structures using femtosecond laser irradiation; however, the details regarding the structures formed by this method have yet to be revealed. In this work, structures were fabricated by focusing and scanning femtosecond laser pulses onto the surface of PDMS. Raman Spectroscopy and Transmission Electron Microscopy (TEM) analyses revealed the formation of silicon carbide (SiC) nanocrystals, as well as multilayer graphitic carbon, in the modified regions of PDMS. The state of the formed material differed depending on the distance from the focal spot, suggesting that photo-thermal effects contributed to the degradation of PDMS into conductive material. Electrical conductivity measurements, in addition to Raman results, indicated that the amount of disorder in the formed graphitic carbon contributes to the electrical conductivity of the fabricated structures.
关键词： PDMS,femtosecond laser,graphitic carbon,electrical conductivity,silicon carbide
更新于2025-09-19 17:13:59
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Ion acceleration from aluminium plasma generated by a femtosecond laser in different conditions
摘要： Non-equilibrium plasma was obtained by irradiating Al foils in vacuum with a femtosecond (fs) laser at intensities of the order of 1018 W/cm2. Protons and other light ions were accelerated in the forward direction by using the target-normal-sheath acceleration regime. Time-of-flight technique was employed to measure the ions' kinetic energy using SiC detectors placed at known distances and angles. The ion acceleration was monitored under different conditions of laser focal position, laser pulse energy, and laser contrast. The target was irradiated using different thicknesses and anti-reflecting graphene films. By optimizing the laser parameters, irradiation conditions, and target properties, it was possible to accelerate up to 2.3 MeV per charge state, as will be presented and discussed.
关键词： aluminium target,femtosecond laser,TNSA,SiC detector,ion acceleration
更新于2025-09-19 17:13:59
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Underwater persistent bubble-assisted femtosecond laser ablation for hierarchical micro/nanostructuring
摘要： In this study, we demonstrate a technique termed underwater persistent bubble assisted femtosecond laser ablation in liquids (UPB-fs-LAL) that can greatly expand the boundaries of surface micro/nanostructuring through laser ablation because of its capability to create concentric circular macrostructures with millimeter-scale tails on silicon substrates. Long-tailed macrostructures are composed of layered fan (central angles of 45-141°) hierarchical micro/nanostructures, which are produced by fan-shaped beams refracted at the mobile bubble interface (≥ 50°light tilt, referred to as the vertical incident direction) during UPB-fs-LAL line-by-line scanning. Marangoni flow generated during UPB-fs-LAL induces bubble movements. Fast scanning (e.g., 1 mm/s) allows a long bubble movement (as long as 2 mm), while slow scanning (e.g., 0.1 mm/s) prevents bubble movements. When persistent bubbles grow considerably (e.g., hundreds of microns in diameter) due to incubation effects, they become sticky and can cause both gas-phase and liquid-phase laser ablation in the central and peripheral regions of the persistent bubbles. This generates low/high/ultrahigh spatial frequency laser-induced periodic surface structures (LSFLs/HSFLs/UHSFLs) with periods of 550-900, 100-200, 40-100 nm, which produce complex hierarchical surface structures. A period of 40 nm, less than 1/25th of the laser wavelength (1030 nm), is the finest laser-induced periodic surface structures (LIPSS) ever created on silicon. The NIR-MIR reflectance/transmittance of fan-shaped hierarchical structures obtained by UPB-fs-LAL at a small line interval (5 μm vs 10 μm) is extremely low, due to both their extremely high light trapping capacity and absorbance characteristics, which are results of the structures’ additional layers and much finer HSFLs. In the absence of persistent bubbles, only grooves covered with HSFLs with periods larger than 100 nm are produced, illustrating the unique attenuation abilities of laser properties (e.g. repetition rate, energy, incident angle, etc.) by persistent bubbles with different curvatures. This research represents a straightforward and cost-effective approach to diversifying the achievable micro/nanostructures for a multitude of applications.
关键词： femtosecond laser,persistent bubble,beam refraction,fan-shaped microstructure,surface structuring,hierarchical micro/nanostructures,LIPSS
更新于2025-09-19 17:13:59
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Femtosecond laser-assisted anterior and posterior capsulotomies in children with persistent hyperplastic primary vitreous
摘要： Anterior and posterior capsulotomies were performed in 12 eyes of 12 patients (age range 3 months to 6 years) with congenital cataracts and primary persistent hyperplastic primary vitreous (PHPV) syndrome using a femtosecond laser. The procedure was performed in 8 eyes with PHPV severity level 1 and 4 eyes with severity level 2 (Sudovsky classification). Surgeries were performed at the Kaluga branch of the S. Fyodorov Eye Microsurgery Federal State Institution, Russia. Postoperative follow-up was between 8 months and 36 months. The use of a low-energy femtosecond laser–assisted posterior capsulotomy in this pediatric population provided safe and predictable results with a reduced number of intraocular manipulations, and reduced the risk for complications.
关键词： persistent hyperplastic primary vitreous,PHPV,pediatric cataract surgery,femtosecond laser,anterior capsulotomy,posterior capsulotomy
更新于2025-09-19 17:13:59
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Patterned arrays of assembled nanoparticles prepared by interfacial assembly and femtosecond laser fabrication
摘要： Creating shape-defined structures of inorganic nanoparticles in a maskless and template-free fashion would advance the engineering of nanoparticle-based devices and structures with desired configurations for various applications. In this work, a novel fabrication protocol combining bottom-up interfacial assembly and subtractive laser patterning was developed for creating patterned arrays of assembled nanoparticles. A solid film of magnetic nanoparticles (10 nm, monodisperse CoFe2O4) was assembled as a nanoparticle film (thickness less than 100 nm) on liquid interface under guiding field, and it was further transferred to Si substrate followed by selective material removal using femtosecond laser pulses, producing patterned arrays (typical size of 3 μm) of assembled nanoparticles. The size, shape, and arrangement of the patterned arrays were finely regulated by adjusting the laser pulse energy and laser scanning path. The magnetization behavior and magnetic anisotropy of the patterned arrays differ from those of the nanoparticle-assembled film, as reflected by the changes of coercivity and squareness along the out-of-plane direction. The presented fabrication protocol is compatible with microelectronic fabrication techniques and can be applied to various inorganic nanoparticles.
关键词： Magnetic properties,Femtosecond laser fabrication,Interfacial assembly,Nanoparticle patterning,Collective properties
更新于2025-09-19 17:13:59
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[IEEE IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium - Yokohama, Japan (2019.7.28-2019.8.2)] IGARSS 2019 - 2019 IEEE International Geoscience and Remote Sensing Symposium - Accurate Ground Positioning Obtained From 3d Data Matching Between Airborne and Terrestrial Data for Ground Validation of Satellite Laser
摘要： We present a phase mask inscription technique with two beam interferometry using a lateral nonhomogeneous beam splitter to create gratings with nonhomogeneous periods, the so-called chirped fiber Bragg gratings. Inscription experiments with deep ultraviolet excimer and femtosecond laser sources reveal how this inscription method depends on the coherence properties of the inscription laser. Nonhomogeneous beam splitters are shown to provide a method to generate chirped fiber Bragg gratings with great wavelength versatility, even with the ultraviolet femtosecond laser.
关键词： two-beam interferometry,Femtosecond laser,fiber Bragg gratings,optical fiber filters
更新于2025-09-19 17:13:59
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Femtosecond laser–assisted intrastromal corneal lenticule implantation for treatment of advanced keratoconus in a child’s eye
摘要： We present a case of a 12-year-old male patient who received a femtosecond laser–assisted intrastromal implantation of a donor lenticule for the treatment of advanced keratoconus. Initially, the uncorrected distance visual acuity (UDVA) in the left eye was counting fingers (CF) and cycloplegic refraction was (cid:1)18.50 (cid:1)4.50 (cid:3) 85 Z 20/400. Preoperative corneal topography demonstrated a curvature of 65.90 (cid:3) 62/57.17 (cid:3) 152. Twelve months after lenticule implantation, the cornea was completely clear and the thickness changed from 245 mm to 639 mm. The UDVA was CF at 2 m and refraction was (cid:1)12.25 (cid:1)2.50 (cid:3) 180 Z 20/30, whereas topography demonstrated a curvature of 61.44 (cid:3) 52/59.28 (cid:3) 142. The results showed that the procedure was successful in thickening and flattening the cornea. It is expected that penetrating or deep anterior lamellar keratoplasty, if required, could be postponed to a more suitable age.
关键词： femtosecond laser,keratoconus,intrastromal corneal lenticule implantation,child
更新于2025-09-19 17:13:59
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High-Efficiency Small Sample Microparticle Fractionation on a Femtosecond Laser-Machined Microfluidic Disc
摘要： The fabrication and testing of microfluidic spinning compact discs with embedded trapezoidal microchambers for the purpose of inertial microparticle focusing is reported in this article. Microparticle focusing channels require small features that cannot be easily fabricated in acrylic sheets and are complicated to realize in glass by traditional lithography techniques; therefore, the fabrication of microfluidic discs with femtosecond laser ablation is reported for the first time in this paper. It could be demonstrated that high‐efficiency inertial focusing of 5 and 10 μm particles is achieved in a channel with trapezoidal microchambers regardless of the direction of disc rotation, which correlates to the dominance of inertial forces over Coriolis forces. To achieve the highest throughput possible, the suspension concentration was increased from 0.001% (w/v) to 0.005% (w/v). The focusing efficiency was 98.7% for the 10 μm particles and 93.75% for the 5 μm particles.
关键词： femtosecond laser,microfluidics,microparticle separation,microfluidic disc
更新于2025-09-19 17:13:59
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Femtosecond Laser-Micromachining of Glass Micro-Chip for High Order Harmonic Generation in Gases
摘要： We report on the application of femtosecond laser micromachining to the fabrication of complex glass microdevices, for high-order harmonic generation in gas. The three-dimensional capabilities and extreme flexibility of femtosecond laser micromachining allow us to achieve accurate control of gas density inside the micrometer interaction channel. This device gives a considerable increase in harmonics’ generation efficiency if compared with traditional harmonic generation in gas jets. We propose different chip geometries that allow the control of the gas density and driving field intensity inside the interaction channel to achieve quasi phase-matching conditions in the harmonic generation process. We believe that these glass micro-devices will pave the way to future downscaling of high-order harmonic generation beamlines.
关键词： femtosecond laser micromachining,attosecond science,high order harmonic generation,de laval gas micro nozzle
更新于2025-09-19 17:13:59
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Direct femtosecond laser surface structuring with complex light beams generated by q-plates
摘要： Direct femtosecond (fs) laser surface structuring became a versatile way to generate surface structures on solid targets demonstrating a high degree of flexibility and controllability in creating different types of structures for many applications. This approach demonstrated an alteration in various properties of the surface, such as optical properties, wetting response, etc. This paper focuses on direct fs laser surface structuring using complex light beams with spatially variant distribution of the polarization and fluence, with emphasis on the results obtained by the authors by exploiting q-plate beam converters. Although striking scientific findings were achieved so far, direct fs laser processing with complex light fields is still a novel research field, and new exciting findings are likely to appear on its horizon.
关键词： femtosecond laser surface processing,LIPSS,vector vortex beams,optical vortex
更新于2025-09-19 17:13:59