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Proof-of-Principle Experiment for Nanoparticle-Assisted Laser Wakefield Electron Acceleration
摘要： Laser electron accelerators have paved the way to build compact electron accelerators, but the quality of the electron beam should be improved to enable efficient use in various specialized applications. We demonstrate a proof-of-principle experiment for nanoparticle-assisted laser wakefield acceleration (NA LWFA) to improve the quality of the electron beam. Nanoparticles are generated through laser ablation of an aluminum target and introduced into a helium plasma to trigger the injection of electrons into the nonlinear plasma wake excited by 70 TW femtosecond laser pulses. We observe a significant enhancement of the electron beam energy, energy spread, and divergence compared with the case of self-injection. For instance, the best quality electron bunches present a maximum energy of up to 340 MeV, with a relative energy spread of 4.7% and a vertical divergence of 5.9 mrad. The initial results on NA LWFA are very promising and motivate further theoretical and experimental research into developing nanoparticle-assisted laser wakefield acceleration.
关键词： femtosecond laser pulses,electron beam quality,plasma wake,nanoparticle-assisted,laser wakefield acceleration
更新于2025-09-19 17:13:59
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Fabrication of grooves on polymer-derived SiAlCN ceramics using femtosecond laser pulses
摘要： In this study, grooves were fabricated on the surface of fully dense polymer-derived SiAlCN ceramics. Industrial femtosecond laser source was used at wavelength of 1030 nm with pulse duration of 290 fs and repetition rate of 100 kHz. Moreover, comprehensive study was carried out to evaluate the influence of scan speed and energy fluence on grooves quality, including the heat-affected zone around the laser-machined grooves, microstructures of laser-irradiated surface, and cross-section morphology of grooves. A series of grooves with width in the range of 30–80 μm and depth below 280 μm was successfully fabricated using femtosecond laser pulse. Laser parameters were optimized to obtain grooves with satisfying surface quality. Furthermore, formation and disappearance of laser-induced periodic surface structures were systematically investigated. This study proposes fabrication of grooves on SiAlCN ceramics via laser processing, which provides precise method for fabrication of microstructure with fascinating properties.
关键词： Laser-induced periodic surface structures,Polymer-derived ceramics,Femtosecond laser pulse,Groove
更新于2025-09-19 17:13:59
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Five-year outcomes of small-incision lenticule extraction vs femtosecond lasera??assisted laser in situ keratomileusis
摘要： To compare the long-term refractive and visual outcomes and the corneal higher-order aberrations of contralateral eyes of patients who received small-incision lenticule extraction (SMILE) in one eye and femtosecond laser–assisted laser in situ keratomileusis (FS-LASIK) in the other eye.
关键词： small-incision lenticule extraction,femtosecond laser–assisted laser in situ keratomileusis,myopic astigmatism,corneal higher-order aberrations,SMILE,FS-LASIK,myopia
更新于2025-09-19 17:13:59
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Engineering black titanium dioxide by femtosecond laser filament
摘要： We propose an approach, by utilizing the propagation of femtosecond laser pulses in the filamentation region in air, to achieve black titanium dioxide (TiO2), a promising material for efficient photocatalysis. It is found that the black TiO2 engineered by femtosecond laser filament in both solution and air environments shows significantly improved absorption in a broad spectral range from 400 to 2500 nm. In addition, the engineered black TiO2 shows a certain degree of enhanced absorption in the microwave range. The structural and elemental analysis of the processed TiO2 suggest that the absorption enhancement is mainly ascribed to the filament-induced disorder and dopant impurity in the surface layer of crystalline TiO2. Our technique provides an alternative way to engineer black TiO2 with the capability of absorbing the solar energy across a broad spectrum that can be useful for various applications in optoelectronics and photochemistry.
关键词： femtosecond laser filamentation,disordered surface,solar energy,titanium dioxide,absorption enhancement,laser processing
更新于2025-09-19 17:13:59
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Experimental study of the effects of femtosecond laser power on the induced-plasma geometry, supercontinuum white light generation and conical emission in air
摘要： This paper presents the experimental investigation of the changes in the geometrical shape of femtosecond laser-induced plasma in air under different laser power, and its effects on supercontinuum white light generation and conical emission. When a femtosecond laser is focused into a tiny spot in air, optical breakdown of air molecules occurs and this leads to the generation of plasma filament whose geometrical size and shape depend on laser power. This process is then followed by two light-emitting processes, namely supercontinuum white light generation and conical emission, both of which scatter light that reveals the characteristics of the plasma filament. Our experiment shows that the laser-induced plasma becomes thinner and longer at high average laser power but appears thick and round at lower laser power. At higher laser power, conical emission which scatters laser light in the forward direction dominates the scattering process while at lower laser power, it is the scattering of supercontinuum white light in all directions that plays a bigger role. The intricate rainbow-like pattern formed on a white screen located far away in the forward direction reveals sophisticated nonlinear optical processes that take place in conical emission which slowly diminishes as the laser power is gradually reduced.
关键词： Femtosecond laser,conical emission,laser-induced plasma,supercontinuum white light
更新于2025-09-19 17:13:59
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Under-oil self-driven and directional transport of water on femtosecond laser-processed superhydrophilic geometry-gradient structure
摘要： Self-driven and continuous directional transport of water droplets in the oil environment has great potential applications in microfluidics, oil-water separation, etc. Nevertheless, most current studies exploit water behaviors occurring in air, and the directional regulation of water under a viscous oil medium remains a challenge. In this work, a superhydrophilic geometry-gradient stainless-steel platform with nanoparticles-covered nanoripples structure is proposed using femtosecond laser direct writing technology. The as-prepared sample spontaneously and directionally transported water droplets in the oil environment from the minor side to the large side of the trapezoidal platform surface, but not in the opposite direction. The transport velocity of water droplets as a function of trapezoid angle and tilt angle of the as-prepared platform was investigated in detail. In addition, the pumpless under-oil water transport platform was successfully prepared on other substrates including Ti and Ni sheets, polyimide film, and C cloth, and exhibited transport capabilities when the platform was flexed and combined into various shapes. This work offers insights for simple fabrication of a flexible and substrate-independent pumpless under-oil directional transport device for water.
关键词： femtosecond laser,superhydrophilic,under-oil,water droplets,directional transport
更新于2025-09-19 17:13:59
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Comparison of optical quality and distinct macular thickness in femtosecond laser-assisted versus phacoemulsification cataract surgery
摘要： Background: Optical quality and macular thickness changing optical quality is rarely reported after femtosecond laser-assisted cataract surgery (FLACS). In current research, we evaluated optical quality recovery and distinct macular thickness changes after FLACS and phacoemulsification cataract surgery (PCS). Methods: A total of 100 cataract patients (100 eyes) were included (50 eyes for the FLACS group and 50 eyes for the PCS group). Modulation transfer function (MTF), point spread function (PSF) and dysfunctional lens index (DLI) were measured by a ray-tracing aberrometer (iTrace). Uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) were also assessed pre-operation,1 week and 1 month after surgery. The MTF values at spatial frequencies of 5, 10, 15, 20, 25 and 30 cycles/degree (c/d) were selected. We used optical coherence tomography (OCT) to assess the macular thickness of different regions pre-operatively and1month after the surgery. Results: In PCS group, we found the statistically significant differences between pre-operation and post-operation in DLI (p < 0.0001), PSF (strehl ratio, SR) (p = 0.027) and MTF (p = 0.028), but not intraocular pressure (IOP) (p = 0.857). The differences between pre-operation and post-operation for DLI (p = 0.031), SR (p = 0.01) and IOP (p = 0.03), but not MTF (p = 0.128) were also found in FLACS group. The differences were statistically significant when the spatial frequencies were at 5, 10 and 25 (p = 0.013, 0.031 and 0.048) between pre-operation and post-operation in PCS group but not FLACS group at 1 month. In PCS group, we found the differences between pre-operation and post-operation in nasal inter macular ring thickness (NIMRT) (p = 0.03), foveal volume (FV) (p = 0.034) and average retinal thickness (ART) (p = 0.025) but not FLACS group at 1 month. Conclusion: FLACS is safe that did not cause significant increase of macular thickness in current study. However, it also cannot produce better optical quality. In contrast, PCS can produce macular thickness changes, but better optical quality recovery. The slightly retinal change may not affect optical quality.
关键词： Macular thickness,Femtosecond laser-assisted cataract surgery (FLACS),Point spread function (PSF),Modulation transfer function (MTF),Phacoemulsification cataract surgery (PCS),Dysfunctional lens index (DLI),Optical quality
更新于2025-09-19 17:13:59
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Quantum dots on demand
摘要： The ability to create and erase three-dimensional patterns of perovskite quantum dots in glass using a femtosecond laser could bring new opportunities in displays, security marking and data storage.
关键词： displays,femtosecond laser,data storage,security marking,perovskite quantum dots
更新于2025-09-19 17:13:59
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Femtosecond laser-integrated anterior segment optical coherence tomography to detect preexisting posterior capsular dehiscence and increase safety in posterior polar cataracts
摘要： To determine the efficacy of the femtosecond laser with integrated anterior segment optical coherence tomography (AS-OCT) for the detection of posterior capsular dehiscence in posterior polar cataracts (PPCs). To evaluate the safety of phacoemulsification in these eyes undergoing femtosecond laser–assisted cataract surgery (FLACS).
关键词： posterior polar cataracts,anterior segment optical coherence tomography,femtosecond laser,posterior capsular dehiscence,phacoemulsification
更新于2025-09-19 17:13:59
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Improvement of ablation capacity of sapphire by gold film-assisted femtosecond laser processing
摘要： Sapphire is widely used in civilian and military equipment owing to its superior optical and mechanical properties. Femtosecond laser has been demonstrated to be an effective tool to process sapphire material. However, the direct processing of sapphire by femtosecond laser still meets some challenges, such as poor ablation morphology and low laser energy absorption. In this work, femtosecond laser processing of sapphire coated with a 12-nm-thick gold film (Au-coated sapphire) has been investigated. The experimental results have revealed that the ablation morphology of Au-coated sapphire has been improved, featuring fewer molten materials and thermal cracks, as well as regular crater shape and uniform periodic surface structures. It has also been found that, under 100 shots condition, the threshold fluence of Au-coated sapphire is reduced by about 56% compared to that of uncoated one. Meanwhile, the incubation effect of Au-coated sapphire is stronger than that of uncoated one. We also illustrate that the material removal rate of Au-coated sapphire is increased up to about two times higher than that of uncoated one. In order to reveal the effective mechanism of the gold film in the laser processing of sapphire, the energy transfer process among incident photons, free electrons and sapphire lattice phonons was studied. Our study provides a guidance for improving the laser ablation capacity of sapphire.
关键词： Gold film,Sapphire,Material removal rate,Ablation morphology,Femtosecond laser processing
更新于2025-09-19 17:13:59