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Femtosecond Laser Pulse Ablation of Sub-Cellular Drusen-Like Deposits
摘要： Age-related macular degeneration (AMD) is a condition affecting the retina and is the leading cause of vision loss. Dry AMD is caused by the accumulation of lipid deposits called drusen, which form under the retina. This work demonstrates, for the first time, the removal of drusen-like deposits underneath ARPE-19 cell layers using femtosecond laser pulses. A novel cell culture model was created in response to the limited access to primary cell lines and the absence of animal models that recapitulate all aspects of AMD. In the cell culture model, deposits were identified with fluorescent stains specific to known deposit constituents. Trains of sub-10 femtosecond laser pulses from a Ti:Sapphire laser were used to successfully ablate the deposits without causing damage to surrounding cells. this drusen removal method can be used as a potential treatment for dry-stage AMD.
关键词： drusen,ARPE-19,laser ablation,age-related macular degeneration,femtosecond laser
更新于2025-09-12 10:27:22
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Direct and Indirect Flap Measurements in Femtosecond Laser–Assisted In Situ Keratomileusis
摘要： To compare direct and indirect LASIK flap thickness measurements using ultrasound and Scheimpflug technology. Eighty-two eyes treated with laser-assisted in situ keratomileusis refractive surgery using a femtosecond laser (IntraLase FS150) were prospectively included in the study. Flap thickness was set to 115 mm. Corneal flap thickness was measured using the direct method—ie, ultrasound pachymetry immediately after flap construction in the presence of cavitation bubbles—and indirect methods, with subtraction of intraoperative post-lift corneal thickness measured using ultrasound pachymetry (intrastroma) from preoperative central corneal thickness using ultrasound (Indirect-US) or Scheimpflug thinnest pachymetry (Indirect-Scheimpflug). Mean flap thickness was overestimated using the indirect methods, Indirect-US and Indirect-Scheimpflug (122.6 6 24.5 mm and 128.1 6 26.1 mm, respectively; P , 0.0060 and P , 0.0001, respectively). There were no significant correlations between the direct and indirect methods. Indirect-Scheimpflug was significantly higher (P = 0.0122) than Indirect-US. The closest average flap thickness compared with the set parameter of 115 mm was that of the direct method (115.6 6 8.6 mm; 95% confidence interval: 21.3 to 2.5; P = 0.5163). The direct method provided the lowest SD of all groups (SD: 8.64). The direct method of flap thickness measurement was the most comparable to the set parameter compared with the indirect subtraction methods. Additional studies are needed to determine which method allows for the most accurate measurement of flap thickness.
关键词： flap thickness,femtosecond laser,laser in situ keratomileusis,Scheimpflug,ultrasound
更新于2025-09-12 10:27:22
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Effective femtosecond laser shock peening on a Mg–3Gd alloy at low pulse energy 430?μJ of 1?kHz
摘要： In this paper, microstructure evolution and hardness of Mg-3Gd alloy treated by femtosecond (fs) laser shock peening (LSP) with direct and con?ned ablation modes were investigated in detail. Under a relatively low pulse energy of 430 μJ with a repetition of 1 kHz, the surface hardness of sample has been enhanced by 70% effectively. Compared with ns-LSP with pulse ?uence of 71.7 J/cm 2 , fs-LSP with pulse ?uence of 34.2 J/cm 2 is superior in the hardness increment, both of which are in the same order of magnitude. A distinct grain re?nement of surface layer has been discovered and results in the increase of hardness. Nonuse of absorption and con?ning layers and the employment of the industry commercial fs laser with high repetition can inspire big potential LSP application in special metal material.
关键词： Mg–3Gd alloy hardness,Laser shock peening,Surface treatment,Femtosecond laser
更新于2025-09-12 10:27:22
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High energy femtosecond laser peening of 2024 aluminum alloy
摘要： A femtosecond laser with a pulse energy of up to 100 mJ is used to investigate the feasibility of laser peening of a 2024 aluminum alloy that is widely used in aerospace industry. Laser beam directly irradiates the as-received aluminum sample surface in air without any protective coating for laser absorption and transparent overlay for plasma confinement. The effects of pulse energy, pulse duration and beam spot size on peening performance are studied. Optical microscope and SEM are used to examine the surface morphology of laser peened samples. Vickers hardness test is used to determine the microhardness on the surface. Residual stresses on the surface and at selected depths are measured using x-ray diffraction method. It is found that femtosecond laser can impart compressive residual stresses to a depth of more than 100 μm for this material, but the surface stress condition is not altered significantly.
关键词： residual stress,aluminum alloy,hardness,femtosecond laser,surface texture,laser peening
更新于2025-09-12 10:27:22
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Parameters Affecting the Welding of Transparent Materials Using Femtosecond Laser Pulses
摘要： There is a pressing need for an accurate process in industrial laser applications such as welding transparent materials. Femtosecond laser pulses, which depend on the nonlinear absorption properties, can be utilized to weld transparent materials. This technique can be applied not only in welding different transparent materials such as glass and polymers, but also in welding opaque materials such as metals, depending on the selection of an appropriate laser wavelength. The parameters that affect the technique such as Keldysh parameter, pulse energy, pulse repetition rate, pulse duration and nonlinear absorptivity were studied. To explain the welding process, an example of an experimental setup and its requirements was described. Besides that, the challenges for the welding process and their voids were also discussed.
关键词： Laser welding,Femtosecond laser,Nonlinear absorption,Transparent materials
更新于2025-09-12 10:27:22
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Femtosecond laser-induced breakdown spectroscopy of a preheated Cu target
摘要： We present a study detailing femtosecond laser-induced breakdown spectroscopy (LIBS) of Cu with the sample preheated to di?erent temperatures (22–120 °C). The detected spectral intensity of the plasma emission increased with the target temperature. Additionally, laser-induced plasma temperature was calculated by Boltzmann plot method. The plasma temperature rose along with the target temperature, indicating an enhanced interaction between the laser and the target in the case of a higher target temperature. We also simulated the thermal behavior of Cu irradiated by the femtosecond laser via a two-temperature model. As the sample temperature increased from 22 °C to 120 °C, the increase in the lattice temperature under femtosecond laser irradiation was approximately 200–300 K, and the ablated depth increased. The simulated results suggested that increasing the sample temperature led to an increase in the ablated mass. Based on this work, it can be seen that the method of preheating the ablation target can help enhance the spectral intensity and the detection sensitivity of femtosecond LIBS.
关键词： LIBS,Sample temperature,Femtosecond laser,Laser-induced breakdown spectroscopy
更新于2025-09-12 10:27:22
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Reversible 3D laser printing of perovskite quantum dots inside a transparent medium
摘要： The three-dimensional (3D) patterning of semiconductors is potentially important for exploring new functionalities and applications in optoelectronics. Here, we show that it is possible to write on demand 3D patterns of perovskite quantum dots (QDs) inside a transparent glass material using a femtosecond laser. By utilizing the inherent ionic nature and low formation energy of perovskite, highly luminescent CsPbBr3 QDs can be reversibly fabricated in situ and decomposed through femtosecond laser irradiation and thermal annealing. This pattern of writing and erasing can be repeated for many cycles, and the luminescent QDs are well protected by the inorganic glass matrix, resulting in stable perovskite QDs with potential applications such as high-capacity optical data storage, information encryption and 3D artwork.
关键词： perovskite quantum dots,optical data storage,femtosecond laser,transparent medium,information encryption,3D laser printing,3D artwork
更新于2025-09-12 10:27:22
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Intraocular lens tilt and decentration after?Nd:YAG laser posterior capsulotomy: Femtosecond laser capsulorhexis versus manual capsulorhexis
摘要： To compare intraocular lens (IOL) tilt and decentration after Nd:YAG laser posterior capsulotomy in eyes that had femtosecond laser–assisted capsulotomy versus manual capsulorhexis. Setting: Ekol Eye Hospital, Izmir, Turkey. Design: Retrospective case series. Methods: Intraocular lens decentration and angle of tilt were measured using a Scheimpflug camera before and 1 month after Nd:YAG capsulotomy. Results: Eighteen eyes had a femtosecond laser–assisted capsulotomy and 25 eyes a manual capsulorhexis. The mean age was 58.2 years G 10.2 (SD) (range 44 to 69 years) and 60.6 G 8.3 years (range 45 to 70 years), respectively. Before capsulotomy, tilt and decentration at both meridians did not differ significantly between the 2 groups (P > .05). After capsulotomy, the angle of tilt was significantly decreased in both groups (femtosecond: vertical 1.5 degrees and horizontal 1.2 degrees; manual: vertical 1.1 degrees and horizontal) and decentration was significantly increased (femtosecond: vertical 0.085 mm and horizontal 0.096 mm; manual: vertical 0.2 mm and horizontal 0.2 mm) at both meridians (P < .05). After capsulotomy, all tilt and decentration parameters were significantly different between the 2 groups (P < .05) except decentration on the horizontal meridian (P Z .669). Conclusions: Nd:YAG posterior capsulotomy performed after femtosecond laser–assisted capsulotomy resulted in better mechanical stability of the IOL. This suggests that a femtosecond laser–created capsulotomy better maintains a proper IOL position. Although the differences were statistically significant, the tilt and decentration values were small and might not be clinically significant.
关键词： tilt,Nd:YAG laser,manual capsulorhexis,intraocular lens,femtosecond laser,decentration,posterior capsulotomy
更新于2025-09-12 10:27:22
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Design and Fabrication of Dual-Scale Broadband Antireflective Structures on Metal Surfaces by Using Nanosecond and Femtosecond Lasers
摘要： Antire?ective surfaces, with their great potential applications, have attracted tremendous attention and have been the subject of extensive research in recent years. However, due to the signi?cant optical impedance mismatch between a metal surface and free space, it is still a challenging issue to realize ultralow re?ectance on a metal surface. To address this issue, we propose a two-step strategy for constructing antire?ective structures on a Ti-6Al-4V (TC4) surface using nanosecond and femtosecond pulsed lasers in combination. By controlling the parameters of the nanosecond laser, microgrooves are ?rst scratched on the TC4 surface to reduce the interface re?ection. Then, the femtosecond laser is focused onto the sample surface with orthogonal scanning to induce deep air holes and nanoscale structures, which e?ectively enhances the broadband absorption. The antire?ection mechanism of the dual-scale structures is discussed regarding morphological characterization and hemispherical re?ectance measurements. Finally, the modi?ed sample surface covered with micro-nano hybrid structures is characterized by an average re?ectance of 3.1% over the wavelengths ranging from 250 nm to 2250 nm.
关键词： nanosecond laser,broadband spectrum,femtosecond laser,micro-nano hybrid structures,antire?ective surfaces
更新于2025-09-12 10:27:22
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Maskless Patterning of Metal Outflow in Alternating Metal/Ceramic Multiple Nanolayers by Femtosecond Laser Irradiation
摘要： In this work, solid-state metal transport from internal metal nanolayers onto the surface of metal/ceramic nano-multi-layers (NMLs) has been directed in a controlled way by femtosecond (fs) laser irradiation and subsequent low temperature thermal annealing. Laser irradiation induced modifications of the NML microstructures and stress states can be limited within the first few top nanolayers due to the focused laser energy input at the metal/ceramic interface by exploiting the local plasmonic effect. Accompanied laser peening can further refine the crystallites and introduce compressive stress at the laser-irradiated region, which reduces the activation energies for vacancy formation and migration of metal atoms in the nano-confinement. Patterned Cu surface nanostructures (outflow) appear selectively along the laser path after air annealing at temperatures down to 360 ℃. For the solid-state diffusion of Cu in confinement, in-plane metal transport along the Cu-AlN interfaces is much faster than the outward short-circuit diffusion of Cu across the AlN barrier layers. Localized metal outflow is accompanied by the collapse and sintering of the remaining AlN barrier layers, under influence of the acting capillary forces, which may further accelerate the metal transport. This laser induced maskless patterning of metal outflow is not only applicable in Cu/AlN NMLs, but also in Ag/AlN NMLs, assisted by subsequent low temperature annealing.
关键词： solid-state metal transport,laser peening,metal/ceramic nanolayers,femtosecond laser,plasmonic effect
更新于2025-09-12 10:27:22