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Evolution of visual acuity, flap thickness, and optical density after laser in situ keratomileusis performed with a femtosecond laser
摘要： To describe the postoperative evolution of visual acuity, flap morphology, and stromal optical density femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). The study comprised 44 consecutive eyes that had FS-LASIK performed with the WaveLight FS200 and the Allegretto excimer laser to correct myopia. Visual outcomes, flap thickness, and stromal optical density were assessed 1 day, 1 week, 1 month, and 3 months postoperatively. A statistically significant improvement in the mean uncorrected distance visual acuity at 1 day (0.94 ± 0.2) and 1 week (0.93 ± 0.2) to 1 month (1.04 ± 0.2) and 3 months (1.11 ± 0.1) postoperatively (P < .05). At 3 months postoperatively, the femtosecond laser had good outcomes in efficacy (0.98 ± 0.1), safety (0.98 ± 0.1), and predictability (100% of eyes were within ± 0.5 D of emmetropia). The femtosecond-created flaps were slightly thicker than intended, the mean SD intraflap was 7.1 μm, the range between the thickest and thinnest points in each flap was 25.4 μm, and the mean flap thickness homogeneity was 7.6 μm at 3 months postoperatively. A progressive decrease in the optical density of the flap stroma and the residual stromal bed was detected during follow-up. The femtosecond laser study appears to be a safe, effective, and predictable platform to obtain LASIK flaps. The flaps were planar and homogeneous but slightly thicker than intended. The optical density of the flap stroma was slightly higher at early follow-up and decreased over time.
关键词： visual acuity,femtosecond laser,LASIK,flap thickness,optical density
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Theoretical Investigation of the Optimal Nonlinear Crystal Thickness for THz Generation from two-Color Laser Pulse Ionized Gas under Different Laser Pulse Parameters
摘要： The generation of terahertz (THz) radiation by two-color laser pulse induced gas plasma is an actively researched topic since its exploration. It is a tabletop, powerful spectroscopic tool in the far-infrared spectral regime. It is possible to generate THz radiation by remotely more than 100m from the laser system, the remote sensing of the THz radiation also possible. Furthermore, the THz spectroscopy is capable to identify chemicals in a nondestructive way. By the combination of the former mentioned features, the THz spectroscopy is a powerful tool to identify drugs, poisons and explosives with remotely in a nondestructive way. One of the drawbacks of the THz radiation generated from two-color laser pulse induced gas plasma is the low efficiency. In the last two decades many publications have been published about increasing the efficiency of this method. Spectrally shaped fundamental beam has been proved to be an effective way to control the generated THz field properties. Using a step phase plate is demonstrated to enhance the generated THz intensity with a factor of two. Combining the fundamental, the second harmonic and the third harmonic beams also increase the THz pulse generation efficiency. Increasing the fundamental laser pulse wavelength has proved to be improve the generation efficiency. In this publication, we examined the nonlinear crystal thickness effect on the THz generation from two-color laser pulse induced gas plasma. It was found the at a given fundamental pulse energy and pulse duration there is an optimal thickness for the nonlinear crystal, where the THz generation is the most effective as seen on Fig. 1. In case of a thinner crystal, than the optimal crystal thickness, the second harmonic generation effectivity decrease, which entails the THz generation effectivity also decrease. In case of thicker crystal, than the optimal crystal thickness, the material dispersion decreases both the fundamental and its second harmonic’s peak power, which entails the THz generation effectivity decrease. The optimal nonlinear crystal thickness was examined in the function of the fundamental laser pulse energy, pulse duration, central wavelength and the nonlinear crystal distance from the focal spot. It was found that all the former mentioned parameters have a great impact on the optimal nonlinear crystal thickness. In conclusion, choosing the proper crystal parameters considering the laser and the setup parameters are a crucial point of the THz generation from two-color laser pulse induced gas plasma.
关键词： optimal thickness,two-color laser pulse,gas plasma,nonlinear crystal thickness,THz generation
更新于2025-09-12 10:27:22
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Custom Optical Coherence Tomography Parameters for Distinguishing Papilledema from Pseudopapilledema
摘要： SIGNIFICANCE: Causes of papilledema can be life-threatening; however, distinguishing papilledema from pseudopapilledema is often challenging. The conventional optical coherence tomography (OCT) scan for assessing the optic nerve often fails to detect mild papilledema. Our study suggests that parameters derived from volumetric OCT scans can provide additional useful information for detecting papilledema. PURPOSE: Optical coherence tomography analysis of the optic nerve commonly measures retinal nerve fiber layer thickness (RNFLT) along a 1.73-mm-radius scan path. This conventional scan, however, often fails to detect mild papilledema. The purpose of this study was to evaluate additional OCT-derived measures of the optic nerve head (ONH) and peripapillary retina for differentiating papilledema (all grades and mild) from pseudopapilledema. METHODS: Cirrus OCT ONH volume scans were acquired from 21 papilledema (15 mild papilledema), 27 pseudopapilledema, and 42 control subjects. Raw scan data were exported, and total retinal thickness within Bruch’s membrane opening (BMO) plus RNFLT and total retinal thickness at the following eccentricities were calculated using custom algorithms: BMO to 250, 250 to 500, 500 to 1000, and 1000 to 1500 μm. Minimum rim width was calculated, and BMO height was measured from a 4-mm Bruch’s membrane reference plane centered on the BMO. RESULTS: Retinal nerve fiber layer thickness from BMO to 250 μm, minimum rim width, and BMO height had significantly greater areas under the receiver operating characteristic curve than did conventional RNFLT for differentiating mild papilledema from pseudopapilledema (P < .0001) and greater sensitivities at 95% specificity. Using cutoff values at 95% specificity, custom parameters detected 10 mild papilledema patients, and conventional RNFLT detected only 1. Bruch’s membrane opening heights above the reference plane were observed in papilledema only, although many papilledema cases had a neutral or negative BMO height. CONCLUSIONS: Using OCT volumetric data, additional parameters describing peripapillary tissue thickness, neuroretinal rim thickness, and ONH position can be calculated and provide valuable measures for differentiating mild papilledema from pseudopapilledema.
关键词： optical coherence tomography,papilledema,optic nerve head,pseudopapilledema,retinal nerve fiber layer thickness
更新于2025-09-12 10:27:22
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Sandwich-structure transferable free-form OLEDs for wearable and disposable skin wound photomedicine
摘要： Free-form optoelectronic devices can provide hyper-connectivity over space and time. However, most conformable optoelectronic devices can only be fabricated on flat polymeric materials using low-temperature processes, limiting their application and forms. This paper presents free-form optoelectronic devices that are not dependent on the shape or material. For medical applications, the transferable OLED (10 μm) is formed in a sandwich structure with an ultra-thin transferable barrier (4.8 μm). The results showed that the fabricated sandwich-structure transferable OLED (STOLED) exhibit the same high-efficiency performance on cylindrical-shaped materials and on materials such as textile and paper. Because the neutral axis is freely adjustable using the sandwich structure, the textile-based OLED achieved both folding reliability and washing reliability, as well as a long operating life (>150 h). When keratinocytes were irradiated with red STOLED light, cell proliferation and cell migration increased by 26 and 32%, respectively. In the skin equivalent model, the epidermis thickness was increased by 39%; additionally, in organ culture, not only was the skin area increased by 14%, but also, re-epithelialization was highly induced. Based on the results, the STOLED is expected to be applicable in various wearable and disposable photomedical devices.
关键词： Keratinocytes,Wearable photomedicine,Skin wound healing,Cell migration,Epidermis thickness,Re-epithelialization,Free-form optoelectronic devices,Sandwich-structure transferable OLED,Cell proliferation
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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Combined parametric optimization of P3HT: PC70BM films for efficient bulk-heterojunction solar cells
摘要： In this report, the effects of photoactive blend compositions, film thicknesses, and annealing conditions on the P3HT:PC70BM solar cells performance and reproducibility was investigated. The performance of prepared devices was described by examining their absorption spectra, current-voltage characteristics and external quantum efficiency (EQE). The thickness of active layer was achieved as 190 nm, 125 nm, and 90 nm, by maintaining the spin speed. Current density (Jsc) slightly increases from 6.39 to 7.15 mA/cm2 with increase in thickness from 90 to 125 nm; however, with further increase in film thickness (190 nm), the Jsc was reduced to 4.39 mA/cm2. To optimize the device performance, four different compositions of PC70BM (1:0.6, 1:0.8, 1:1, and 1:12) were investigated at the most favorable film thickness ~ 125 nm. The effect of different PC70BM compositions on photovoltaic performance was demonstrated by X-ray diffraction (XRD) and Raman measurements that illuminated modification in structural properties. Additionally, annealing condition led to achieve the good phase separation for efficient charge separation and transport within P3HT: PCBM film which further leads to increased efficiency (PCE ~ 3.31%). These effects deliver valued facts for the choices of PC70BM amount in P3HT:PC70BM system, and this efficient device optimization might be useful in other efficient photovoltaic systems for better performance through excellent reproducibility.
关键词： P3HT:PC70BM,Composition,Film thickness,Solar cells,Photoactive layer
更新于2025-09-12 10:27:22
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Influence of adaptive slice thickness and retained heat effect on laser metal deposited thin-walled freeform structures
摘要： Light-weight, thin-walled freeform structures of aerospace materials can be realized through Additive Manufacturing process like powder- and wire-based Laser Metal Deposition (LMD) technique. Repeatability, in the context of deposited clad geometry and achieved microstructure hinders the wide-spread industrialization of high deposition rate LMD process, which is influenced by numerous intrinsic and extrinsic process parameters. In this paper, the influences of adaptive slice thickness and retained heat effect on build geometry and microstructure have been investigated. Experiments carried out with a powder-fed LMD system to build Ti-6Al-4V freeform structures have been examined for geometrical accuracy and microstructure analysis.
关键词： Layer-to-layer control,High deposition rate,Adaptive slice thickness,Retained heat effect,Laser Metal Deposition
更新于2025-09-12 10:27:22
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Fabrication of efficient CsPbBr3 perovskite solar cells by single-source thermal evaporation
摘要： It is promising to improve the stability of organic–inorganic hybrid halide perovskite solar cells by using all-inorganic perovskite materials. Herein, a facile one-crucible single-source vacuum thermal evaporation (VTE) approach is developed, which is used to evaporate two different melting points materials CsBr (630 °C) and PbBr2 (370.6 °C) to deposit high-quality inorganic CsPbBr3 perovskite films. Molar ratio of PbBr2 to CsBr in their mixture in the crucible is a key factor influencing the stoichiometry, structure, photoelectrical and photovoltaic properties of the CsPbBr3 films. The other important factor is the thickness of the CsPbBr3 films. High-quality CsPbBr3 films with good uniformity and compact and large grains are prepared. Planar CsPbBr3 perovskite solar cells are fabricated giving a high power conversion efficiency of 8.65%. The fabricated CsPbBr3 solar cells exhibit a good stability in air without encapsulation. This study opens up the possibility to deposit multi-element compound thin films by facile single-source VTE of different melting points materials.
关键词： Solar cells,Single-source evaporation,Thickness,Molar ratio,CsPbBr3 films
更新于2025-09-12 10:27:22
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Interfacial crosslinked controlled thickness graphene oxide thin-films through dip-assisted layer-by-layer assembly means
摘要： The augmentation of research in graphene based thin films has been of great interest to various current industrial stakeholders. This is mainly due to the wide scope of films applications, ranging from nanoelectronics to separation membranes. Therefore, establishing a relation between graphene based thin film key characteristics and the fabrication operating conditions is of high significance. This study entails the successful fabrication of controlled-thickness crosslinked graphene oxide (GO) thin films on inexpensive silicon-based glass slide substrates. The method of film fabrication used is the dip-assisted layer-by-layer assembly, which has an added advantage of step-control of thin film thickness, good film uniformity and continuity. The thickness was primarily tuned through the use different sized crosslinkers; a covalent based sub-nanometer sized p-phenylenediamine and an electrostatic based polyethyleneimine on an interchangeable assembly with GO. Pre film fabrication, Fourier Transform Infra-Red and X-Ray Photoelectron Spectroscopy characterizations were carried out to determine the nature of interactions between GO and the crosslinkers. Post film fabrication, scanning electron microscopy, water contact angle measurements and profilometry analysis were undertaken for film continuity, hydrophilicity and thickness measurements respectively. A strong linear trend between film thickness of the differently crosslinked films and the number of bi-layers was established.
关键词： Graphene oxide,Thin film,Crosslinking,Thickness,Layer-by-layer
更新于2025-09-12 10:27:22
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Thickness validation of modeling tools for laser cutting applications
摘要： Laser cutting of metal sheets is a well-established industrial process, however, major process changes are constantly being introduced by newer technologies, e.g. new laser technologies, higher power sources, polarization and beam shaping control units, and gas flow optimizations. The multi-physical nature of the laser cutting process makes detailed simulations complex and demanding in terms of computational and implementation efforts. The gap between accurate modeling and industrial requirements makes an experimental approach often more economically realistic. Nevertheless, efficient assessment models that utilize a trade-off between model complexity and accuracy of the response to be assessed are attractive. Such models can be used for further technological development by efficiently supporting engineers in designing and selecting optical systems. This paper revisits model assumptions of an in-house developed laser cutting model as it is validated for larger thicknesses. This model assesses polarization and beam shaping effects on the cutting performance of thin sheets. In this work, dedicated cutting experiments to assess the maximum cutting speed of stainless steel 304L of 2, 6, and 10 mm thickness for a wide range of focal point positions are conducted and compared to the model prediction. The results show that R2 of this comparison decreases from 0.99 for 2 mm thickness, to 0.58 for 10 mm. It can be concluded that the trend prediction accuracy degrades for thicker plates. Analysis of the experiments and simulation data for 10 mm plates reveals two possible phenomena that become more important with thickness: multiple reflections and instability of the melt flow dynamics.
关键词： Thickness,Modelling,Prediction,Maximum cutting speed,Laser cutting
更新于2025-09-12 10:27:22