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Mechanism and Experimental Study of Femtosecond-Laser Super-Resolution Processing Based on Beam Shaping Technology
摘要： The three-dimensional microsolid can be fabricated by scanning point-by-point inside the polymer material according to the predetermined trajectory in femtosecond-laser two-photon direct writing mode. In the process of machining, the shape and intensity distribution of focus spot are changed by some processing parameters, which a?ect the processing accuracy and surface quality. Based on Fresnel di?raction theory and the intensity distribution function of focal spot, the focal spot shape is simulated and the main factors a?ecting the light intensity distribution are analyzed theoretically and simulated numerically. We propose a shaping method to improve the asymmetric shape of the facula by adding a prefocusing lens. According to the mechanism of femtosecond-laser super-resolution processing, we propose a beam shaping method using four-ring complex transmittance phase plate to achieve super-resolution processing. The phase plate was optimized on the global optimization algorithm and genetic algorithm. The validation experiment was carried out by scanning the photochromic material ?lm with pulsed laser and reading the ?uorescence signal of the photochromic point with single photon confocal. The experimental results show that the facula distribution is approximately symmetrical, and the size of facula is decreased obviously. The compression ratio is basically consistent with the theoretical calculation results. Therefore, super-resolution processing can be achieved by adding pre-focusing lens and phase plate to shaping the laser beam. The results of theoretical and experimental studies provide su?cient basis for improving the machining accuracy and surface quality of microdevices.
关键词： beam shaping,femtosecond laser,super resolution,microfabrication
更新于2025-09-23 15:21:01
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Femtosecond Lasera??Etched MXene Microsupercapacitors with Doublea??Side Configuration via Arbitrary Ona?? and Througha??Substrate Connections
摘要： The capacitance of microsupercapacitors (MSCs) can double if both sides of substrates are used to construct MSCs. Nevertheless, achieving electric connections of MSCs through substrates is a challenge due to the difficulty in precisely positioning each MSC couple that has two of the same MSCs units on two sides. In this work, taking advantage of the synchronous etching on both sides of transparent polyethylene terephthalate substrates by femtosecond laser pulses, a double-sided configuration is attained with high precision in the alignment of back-to-back MSC couples and versatile double-side MSCs are realized via arbitrary on- and through-substrate connections of MXene MSC units. The MXene double-side MSC fabricated by the series connection of 12 spiral pattern MXene MSC units with interdigital electrodes of 10 μm width interspace can output a large working voltage of 7.2 V. Additionally, femtosecond laser etching brings the transformation of MXene into titania near-etched edges with a lateral distance less than 1 μm. Such a small laser-affected area has little influence on the capacitive performance, which is one of advantages for femtosecond laser over conventional lasers. This research is valuable for one-step manufacturing of highly integrated MSCs in the field of miniaturized energy storage systems.
关键词： double-sided,microsupercapacitors,femtosecond laser etching,MXene MSCs,MSCs,high integration
更新于2025-09-23 15:21:01
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Unseeded velocimetry in nitrogen for high-pressure, cryogenic wind tunnels: part III. Resonant femtosecond-laser tagging
摘要： Selective two-photon absorptive resonance femtosecond laser electronic excitation tagging (STARFLEET) velocimetry is characterized for the first time at high-pressure, low-temperature conditions. Studies were carried out in the NASA Langley Research Center’s 0.3 meter transonic, cryogenic wind tunnel, with flow conditions spanning the entire operational envelope of the facility; total pressures ranging from 100 kPa to 517 kPa, total temperatures from 80 K to 327 K, and Mach numbers from 0.2 to 0.85. STARFLEET signal intensity and lifetime measurements are examined for their thermodynamic dependencies since both intensity and lifetime have implications for measurement precision. Signal intensity is found to be inversely proportional to density, while lifetime scales nearly linearly with density until approaching the liquid-vapor saturation point of nitrogen. The velocity measurement accuracy and precision are assessed over the full domain of conditions, and standard error was determined to be 1.6%, while precision ranged from roughly 1.5% to 10% of the freestream velocity. The precision was also observed to have a temperature dependence, likely a result of the longer lifetimes experienced at higher densities.
关键词： femtosecond laser,resonant excitation,molecular tagging velocimetry
更新于2025-09-23 15:21:01
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The role of the femtosecond laser induced nano/micro structures on the optical features of the steel surface; experimental polarimetry study
摘要： We are witnessing that ultrashort laser material processing (ULMP) is getting an established technique to modify many characteristics of a surface. Being applicable for various materials with any geometry or physical characteristics, besides being rapid and having simple experimental set-ups makes ULMP appropriate for small and large scale controlled modifications. Using this method to adjust the optical features of a surface has been also suggested in last years. So that mimicking the functional surfaces existing in nature which have distinctive surface morphologies and thus have special optical features, efforts are going on to create similar samples using ULMP. Here in this study, the potential of ULMP technique in changing the optical properties of metallic substrates is explored. Selecting 316L stainless steel as a substrate, five samples which are irradiated in different circumstances are fabricated. The role of the laser induced nano/micro structures on the optical features of these samples are studied systematically. Visible light backscattering in the range of 0°-65° was studied at first. Extracting the Mueller matrix elements for all samples at two different incident angles of 45° and 60°, the polarimetry parameters including retardancy, depolarization and diattenuation are calculated at the next step. Due to the multi-scale nature of the morphologies, more than the illuminating light angle, dependence of the samples optical response to its orientation is also discussed in detail Results clearly reflect that the optical response of laser induced periodic surface structure (LIPSS) coated layers have an anisotropic behavior regarding the incident angle and the polarization of the illuminating light. Furthermore, the surface orientation itself can play very serious role on the final response of the sample. It comes out that the characteristics of a surface such as its morphology, roughness or the correlation of the LIPSS structures has important effect in these regards.
关键词： backscattering,structure,femtosecond laser,surface,optical features,polarimetry
更新于2025-09-23 15:21:01
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Comparison of quantitative analyses using SIMS, atom probe tomography, and femtosecond laser ablation inductively coupled plasma mass spectrometry with Si <sub/>1a??X</sub> Ge <sub/>X</sub> and Fe <sub/>1a??X</sub> Ni <sub/>X</sub> binary alloys
摘要： Due to their electrical and physical properties, Si1?XGeX materials are widely used in microelectronic devices. In particular, the Ge component found within Si1?XGeX compounds is important for enhancing carrier mobility and altering the lattice constant of metal-oxide-semiconductor field-effect transistors. In this study, magnetic sector secondary ion mass spectrometry (magnetic sector SIMS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used to determine the accurate concentrations of major compositions present within binary alloy samples. However, quantitative SIMS analysis is limited by the matrix effect, which influences the sputter yield of an element in a compound and alters the secondary ionization yields. Quantitative deviations that were due to the matrix effect were reduced by using Cs cluster ions (MCs+ and MCs2+) instead of elemental ions; the SIMS results using the elements were, therefore, compared with those using MCs+ and MCs2+ cluster ions. In the case of Fe1?XNiX alloys that have a less matrix effect compared to Si1?XGeX alloys, both the Cs primary ion beam (Cs+) and an oxygen primary ion beam (O2+) were used to measure the Fe1?XNiX compositions. The quantitative results from the two different primary ion beams were then compared to understand the ionization process. Deviations in the quantitative values gained with the O2+ beam were lower than those obtained using the Cs+ primary ions, meaning that using oxygen as the primary ion improves the accuracy in quantifying Fe1?XNiX compounds. Other reliable tools for analysis such as atom probe tomography and femtosecond laser ablation inductively coupled plasma mass spectrometry were also used in the quantitative analysis, with results that were consistent with the most accurate results obtained using magnetic sector SIMS and ToF-SIMS.
关键词： Si1?XGeX,femtosecond laser ablation inductively coupled plasma mass spectrometry,atom probe tomography,SIMS,Fe1?XNiX,binary alloys
更新于2025-09-23 15:21:01
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Ultrafast Laser Processing of Nanostructured Patterns for the Control of Cell Adhesion and Migration on Titanium Alloy
摘要： Femtosecond laser texturing is a promising surface functionalization technology to improve the integration and durability of dental and orthopedic implants. Four different surface topographies were obtained on titanium-6aluminum-4vanadium plates by varying laser processing parameters and strategies: surfaces presenting nanostructures such as laser-induced periodic surface structures (LIPSS) and ‘spikes’, associated or not with more complex multiscale geometries combining micro-pits, nanostructures and stretches of polished areas. After sterilization by heat treatment, LIPSS and spikes were characterized to be highly hydrophobic, whereas the original polished surfaces remained hydrophilic. Human mesenchymal stem cells (hMSCs) grown on simple nanostructured surfaces were found to spread less with an increased motility (velocity, acceleration, tortuosity), while on the complex surfaces, hMSCs decreased their migration when approaching the micro-pits and preferentially positioned their nucleus inside them. Moreover, focal adhesions of hMSCs were notably located on polished zones rather than on neighboring nanostructured areas where the protein adsorption was lower. All these observations indicated that hMSCs were spatially controlled and mechanically strained by the laser-induced topographies. The nanoscale structures influence surface wettability and protein adsorption and thus influence focal adhesions formation and finally induce shape-based mechanical constraints on cells, known to promote osteogenic differentiation.
关键词： cell adhesion,multiscale-patterning,wettability,human mesenchymal stem cell,femtosecond laser,cell spreading,cell motility,protein adsorption
更新于2025-09-23 15:21:01
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Fabrication of oila??water separation copper filter by spatial light modulated femtosecond laser
摘要： Surface with oil-water separation performance has attracted more and more attention in the application of oil-containing wastewater purification. Much related work has been done by many researchers. However, there are still many difficulties in rapid manufacturing of filter membranes with special wettability. In this paper, an efficient, flexible method to fabricate microporous arrays by using femtosecond (fs) laser combined with spatial light modulator (SLM) is proposed. The laser treated copper sheet surface shows hydrophobic and superoleophilic properties due to the microstructure. Meanwhile, the array of micro-through-holes on the surface can allow oil to penetrate through holes and prevent water from penetrating. The manufacturing process is not only extremely efficient, 10×10 focus array are used in the ablation, but also it is without chemical method and the filter presents a long-term stable hydrophobic and superoleophilic performance.
关键词： Superoleophilic,Oil-water separation,Hydrophobic,Spatial light modulator,Femtosecond laser
更新于2025-09-23 15:21:01
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Microscopic Mechanisms of Femtosecond Laser Ablation of HMX from Reactive Molecular Dynamics Simulations
摘要： With ultrashort duration and ultrahigh energy, femtosecond laser (fs-laser) pulses are very promising for the precision machining of energetic materials. Compared with the mechanical machining methods of energetic materials, fs-laser machining technology has the advantages of high safety, high precision and absence of pollution. A deep understanding of the mechanisms between fs-lasers and energetic materials is the basis for the development of fs-laser machining technology. In this paper, the method of reactive molecular dynamics (ReaxFF-MD) was adopted to calculate the fs-laser ablation process of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX, a high explosive compound), and the ablation mechanisms of HMX under different fs-laser energies were studied. The results show that the fs-laser ablation mechanisms of HMX are related to the laser power density. When the laser power density is high enough (3.4×1014 W/cm2, 1.0 mJ/pulse), HMX undergoes ionization or decomposition reactions at the picosecond level (~7.65 ps) and produces a high temperature and pressure plasma. Many N, H and O single atoms and their ionic products occurs along with some small molecular fragments of NO2, H2O, CO2, N2, H2, NH, NH2, CO, OH, CNO2 and very few toxic products of NO and HNO2. In this case, the removal process of HMX occurs via a phase explosion mechanism. As the laser energy decreases, the ionization degree of ablation products decreases, in which the number of monoatomic and ionic products decreases, while the number of toxic small molecules (such as NO, HNO2, and HNO) increases. When the laser power density is relatively low (0.34×1014 W/cm2, 0.1 mJ/pulse), the removal process of HMX occurs via a photomechanical mechanism, and the compound escapes as intact initial HMX molecules. When the laser power density is close to the ablation threshold of the explosive, the HMX molecules only undergo a melting state to some extent without escaping from the surface of the crystal. Therefore, the fs-laser can be used in the precise machining of explosives and preparation of high-purity energetic nanomaterials by a reasonable selection of fs-laser energy.
关键词： energetic materials,ReaxFF-MD,femtosecond laser,HMX,ablation mechanisms
更新于2025-09-23 15:21:01
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Systematic review and meta-analysis of femtosecond lasera??enabled keratoplasty versus conventional penetrating keratoplasty
摘要： Purpose: The aim of this meta-analysis is to compare femtosecond laser–enabled keratoplasty with conventional penetrating keratoplasty regarding postoperative astigmatism, visual functions, graft rejection, graft failure, and complications. Methods: Eligible studies were retrieved from five mainstream electronic databases, including PubMed, Embase, Ovid MEDLINE, Cochrane Library, and ClinicalTrial.gov. Postoperative topographic astigmatism was set as the primary outcome, and best-corrected visual acuity, spherical equivalent, endothelial cell density, graft rejection, graft failure, and complications were chosen as the secondary outcomes. Standard mean difference and risk ratio were the size effects for continuous data and binomial data, respectively. The data were pooled through either the random-effects model or the fixed-effects model based on data heterogeneity. Moreover, subgroup analyses were conducted when the heterogeneity occurred distinctly (I2 > 50%). Results: A total of seven comparative studies were included. The pooled standard mean difference (?0.32, 95% confidence interval: ?0.74 to 0.10) showed that femtosecond laser–enabled keratoplasty was not superior over conventional penetrating keratoplasty to decrease postoperative topographic astigmatism (p = 0.14). However, best-corrected visual acuity after femtosecond laser–enabled keratoplasty was significantly better than that after conventional penetrating keratoplasty (p = 0.00, standard mean difference: ?0.23, 95% confidence interval: ?0.37 to ?0.10). Furthermore, endothelial cell density after femtosecond laser–enabled keratoplasty was preserved significantly better (p = 0.03, standard mean difference: 0.63, 95% confidence interval: 0.07–1.20). Moreover, spherical equivalent, graft rejection, graft failure, and complications represented no distinct differences between femtosecond laser–enabled keratoplasty and conventional penetrating keratoplasty (p > 0.05). Conclusion: Femtosecond laser–enabled keratoplasty may not be superior over conventional penetrating keratoplasty in decreasing postoperative topographic astigmatism, but might have advantages to achieve best-corrected visual acuity and endothelial cell density preservation. In addition, the two techniques seem to be comparable regarding spherical equivalent, graft rejection/failure, and complications.
关键词： Astigmatism,meta-analysis,femtosecond laser–enabled keratoplasty,conventional penetrating keratoplasty,cornea
更新于2025-09-23 15:21:01
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Laser-assisted in-situ keratomileusis (LASIK) with a mechanical microkeratome compared to LASIK with a femtosecond laser for LASIK in adults with myopia or myopic astigmatism
摘要： Laser-assisted in-situ keratomileusis (LASIK) is a surgical procedure that corrects refractive errors. This technique creates a flap of the outermost parts of the cornea (epithelium, bowman layer, and anterior stroma) to expose the middle part of the cornea (stromal bed) and reshape it with excimer laser using photoablation. The flaps can be created by a mechanical microkeratome or a femtosecond laser.
关键词： mechanical microkeratome,femtosecond laser,myopic astigmatism,LASIK,myopia
更新于2025-09-23 15:21:01