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Femtosecond Laser-Assisted Penetrating Keratoplasty for Treating Infective Keratitis
摘要： To report the results of penetrating keratoplasty (PKP) assisted by femtosecond laser in the treatment of persistent infective keratitis. Seven eyes of 7 patients with diagnosed infective keratitis were recruited. They showed no improvement on maximal medical therapy for a week. The causative organisms were Pseudomonas aeruginosa in 3 cases and Fusarium in 4 cases. All cases underwent femtosecond laser-assisted PKP with a mushroom-shaped cut. Post-operative antimicrobial medications were continued for 8–12 weeks. Sutures were removed after 6 months. Therapeutic success was de?ned as eradication of primary infection. Functional success was considered when visual function improves to 20/200 or better. All 7 eyes underwent femtosecond laser-assisted PKP. There were no intraoperative complications, and all patients had uneventful recipient cornea separation. Anatomic, therapeutic, and functional success was achieved in all patients. During the 6-month follow-up period, no recurrence of infection was reported. The average preoperative corrected distance visual acuity (CDVA) was 2.07 log of the minimal angle of resolution (LogMAR) 6 0.21, whereas at 6 months postoperatively, the average CDVA was 0.17 LogMAR 6 0.13, with a P value of 0.00025. Femtosecond laser-assisted PKP was found to be an effective method for treating infective keratitis (particularly that caused by Pseudomonas aeruginosa and Fusarium) that did not respond to medical treatment. Early surgical intervention before the disease becomes advanced is recommended.
关键词： therapeutic penetrating keratoplasty TPK,penetrating keratoplasty,resistant keratitis,femto-keratoplasty,femtosecond laser,antifungal therapy,Pseudomonas aeruginosa,infective keratitis,Fusarium
更新于2025-09-12 10:27:22
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Femtosecond Laser Ablation Synthesis of Nanoparticles and Nano-Hybrides in Ethanol Medium
摘要： The nanoparticle production has a significant importance because of its unique optical properties in molecular biology and medicine. Plasmonic metallic nanoparticles are widely used in cancer monitoring studies as contrast agents on the account of their surface plasmon resonance (SPR) effect. Beside, silicon (Si) semiconductor nanoparticles can provide several beneficial properties that they are used commonly intensifying the detecting signals. Nanoalloys/Nanohybides/Nanocomposites are more functional materials than a single material structure and having many restrictions. At that point, the application of Pulsed Laser Ablation (PLA) technique has many advantages if applied in the liquid. Since no any chemical technique is applied, this procedure promises a clean synthesis process; it is a simple and economical technique in the production process. It provides some possibilities to generate particles in the desired size, shape and density, and these properties of nanoparticles produced can be controlled by controlling the laser parameters. In this work, we have focused on the production of nanoparticles to rid off chemical processes using femtosecond laser ablation technique, and this technique presents a process to reach the fast and reliable results for production of nanoshells, nanocomposites and all nanoforms of particles. We have produced Si@Au nanohybrids in ethanol medium using femtosecond laser ablation depending on laser pulse energy. Absorption spectra were recorded day by day to determine the optical characteristics of produced nanoparticles within these time durations, Transmission Electron Microscopy (TEM) images were obtained for monitoring and determining the size/structure of nanoparticles, energy dispersive spectroscopy (EDS) for material compositions were produced, these results obtained are presented in the scope of this paper.
关键词： silicon,ablation,femtosecond laser,gold,Nanoparticle
更新于2025-09-12 10:27:22
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Wettability analysis of water on metal/semiconductor phases selectively structured with femtosecond laser-induced periodic surface structures
摘要： Femtosecond (fs) laser-induced periodic surface structures (LIPSS) were selectively generated on the surface of an Ag-Si alloy consisting of a metallic and a semiconducting phase. For this purpose, the alloy was irradiated with linearly polarized fs-laser pulses (τ = 300 fs, λ = 1025 nm, frep = 100 kHz) using a laser peak fluence F = 0.30 J/cm2. Due to the different light absorption behavior of the semiconductor (Si) and the metal (Ag) phase that results in different ablation thresholds of the respective phase, pronounced LIPSS with a period of Λ ≈ 950 nm and a modulation depth of h ≈ 220 nm were generated solely on the Si phase. The alloy surface was characterized by scanning electron microscopy, optical microscopy, white light interference microscopy and atomic force microscopy before and after laser irradiation. Chemical analysis was carried out by energy dispersive X-ray spectroscopy, revealing surface oxidation of the Si phase and no laser-induced chemical modification of the Ag phase. The surface wettability of the alloy was evaluated with distilled water and compared to the single constituents of the composites. After fs-laser irradiation, the surface is characterized by a reduced hydrophilic water contact angle. Furthermore, the alloy selectively structured with LIPSS revealed a droplet shape change due to the distinctly different contact angles on the Si (θ = 5°) and the Ag (θ = 74°) phase. This phenomenon was evaluated and discussed by local contact angle analyses using a confocal laser scanning microscope and a Rhodamine B dye. In addition, it was shown that the shape change due to different contact angles of the components allowed a targeted droplet movement on a macroscopic material boundary (Ag/Si) of the alloy. Selectively structured metal/semiconductor surfaces might be of particular interest for microfluidic devices with a directional droplet movement and for fundamental research of wettability.
关键词： Contact angle,Wettability,Microfluidic devices,LIPSS,Ag-Si alloy,Femtosecond laser
更新于2025-09-12 10:27:22
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Femtosecond Laser-Produced Underwater “Superpolymphobic” Nanorippled Surfaces: Repelling Liquid Polymers in Water for Applications of Controlling Polymer Shape and Adhesion
摘要： A femtosecond (fs) laser-ablated surface that repels liquid polymer in water is reported in this paper. We define this phenomenon as the “superpolymphobicity”. Three-level microstructures (including microgrooves, micromountains/microholes between the microgrooves, and nanoripples on the whole surface) were directly created on the stainless steel surface via fs laser ablation. A liquid polydimethylsiloxane (PDMS) droplet on the textured surface had the contact angle of 156 ± 3° and contact angle hysteresis less than 4° in water, indicating excellent underwater superpolymphobicity of the fs laser-induced hierarchical microstructures. The contact between the resultant superhydrophilic hierarchical microstructures and the submerged liquid PDMS droplet is verified at the underwater Cassie state. The underwater superpolymphobicity enables to design the shape of cured PDMS and selectively avoid the adhesion at the PDMS/substrate interface, different from the previously reported superwettabilities. As the examples, microlens array and microfluidics system were prepared based on the laser-induced underwater superpolymphobic microstructures.
关键词： superhydrophilicity,polymer repellence,three-level microstructure,femtosecond laser,underwater superpolymphobicity
更新于2025-09-12 10:27:22
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High-Speed All-Optical Modulator Based on a Polymer Nanofiber Bragg Grating Printed by Femtosecond Laser
摘要： On-chip optical modulator for high-speed information processing system has been widely investigated by majority of researchers but the connection with the fiber system is a difficulty. The fiber-based optical modulator is a good solution to this problem. Fiber Bragg Grating has good potential to be used as an optical modulator because of its linear temperature response, narrow bandwidth, and compact structure. In this paper, a new fiber-integrated all-optical modulator has been realized based on a polymer nanofiber Bragg grating printed by femtosecond laser. This device exhibits a fast temporal response of 176 ns and a good linear modulation of -45.43 pm/mW. Moreover, its stability has also been studied. This work firstly employs Bragg resonance to realize a fiber-integrated all-optical modulator and paves the way toward realization of multifunctional lab-in-fiber devices.
关键词： polymer fiber,all-optical modulator,fiber Bragg grating,femtosecond laser micromachining,multi-photon polymerization
更新于2025-09-12 10:27:22
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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) - Fabrication of Tuned Lipss-Based Metallic Polarization Gratings
摘要： Surface nanostructuring has received increasing attention in recent years due to the wide range of applications in which it offers advantages. Particularly, Laser-Induced Periodic Surface Structures (LIPSS) have proven useful for surface functionalization [1]. LIPSS are periodic formations generated in most materials when irradiated with linearly polarized radiation. The orientation of these structures is directly linked to the polarization of the incident light, while other parameters of their morphology such as period and depth can be controlled with the number of pulses, fluence, wavelength and pulse duration of the incident light. Due to their periodic nature, LIPSS behave optically as nanogratings [2], which have been largely studied as polarization converters (or Polarization Gratings, PGs). PGs are structures that introduce a phase shift in the incident light, which produces a change in its polarization state [3]. Therefore, PGs have potential applications as reflective waveplates [4], showing advantages over transmission waveplates such as higher damage thresholds and a lower temporal dispersion of the pulse. So far, PGs have been fabricated with methods such as direct laser interference or lithography [5]. The main drawbacks of these methods include limited choice of periods for the generated structures or a complex and environmentally unfriendly fabrication process, which could be overcome by a fabrication method based on LIPSS. In order to fabricate LIPSS-based PGs, stainless steel samples were irradiated with a 800 nm femtosecond Ti:Sapphire laser. The laser was focused onto the surface of the sample through a cylindrical lens with a focal length of 10 cm. The sample was translated perpendicular to the laser beam with a mechanical stage at a constant speed, generating LIPSS in a large area of 5 mm x 5 mm in a few seconds. By varying the fluence of the beam and the speed of the stage, LIPSS with different parameters were fabricated. Topography of the samples were characterized with AFM and SEM (Fig. 1a) microscopes, and polarization conversion and reflectivity were examined with a polarimeter. Results show that a gradual change in LIPSS morphology is associated to a gradual change in the ellipticity of the laser beam (Fig. 1b). It is also observed that LIPSS geometry changes smoothly with processing parameters. Therefore, it is proven that LIPSS-based PGs can be fabricated experimentally, and that the properties of such PGs can be tuned changing the LIPSS geometry, as expected. These results are in good agreement with the performed FDTD simulations for different LIPSS morphologies.
关键词： Surface nanostructuring,Polarization Gratings,LIPSS,Polarization conversion,Femtosecond laser
更新于2025-09-12 10:27:22
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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) - Broadband Mid-Infrared Directional and Multimode Interference Couplers in GLS Glass Fabricated using Femtosecond Laser Direct-Writing
摘要： The first broadband directional and multimode interference couplers for the mid-infrared centred around 4 μm wavelength are demonstrated. The devices are inscribed into commercial chalcogenide glass (Gallium-Lanthanum-Sulfide, GLS) provided by the University of Southampton using a tightly focused 800 nm, 5.1 MHz repetition rate femtosecond laser. Low loss waveguides are formed by placing 3 individual laser written tracks next to each other, resulting in propagation losses as low as 0.22 dB/cm. These waveguides are used to create asymmetric directional couplers, where the propagation constant in one arm is tailored to flatten the chromatic response of the device. By locally changing the feedrate at which the sample is translated through the focus, a change in propagation constant is obtained in the coupling region of the device. This yields a 3 dB coupler with a wavelength flattened response over a 500 nm wavelength band for ±5% variation in the coupling ratio compared to < 200 nm for a symmetric directional coupler. Multimode interference couplers were created by placing 26 laser inscribed tracks next to each other to form a 140 μm wide multimode interference region with lengths ranging from 5 to 10 mm. Asymmetry inside the multimode interference regions induced by the sequential writing process results in port dependent cross coupling ratios. Yet, close to 3 dB coupling was found for an 8.1 mm long device when injecting into the left input. The device features nearly perfect achromaticity across 3.75 to 4.25 μm.
关键词： GLS glass,mid-infrared,multimode interference couplers,femtosecond laser direct-writing,directional couplers
更新于2025-09-12 10:27:22
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Experimental and analytical evaluation of the acoustic radiation of femtosecond laser plasma filament sound sources in air
摘要： Plasma ?laments in air induced by femtosecond laser pulses lead to the generation of strong shock waves. This letter presents a systematic study, both experimental and theoretical, of the acoustic radiation by femtosecond laser-generated ?laments. A theoretical model is developed based on the experimental results and is used to evaluate the directivity of the ?lament’s acoustic radiation within and beyond the audible frequency range. It is shown that the acoustic directivity of plasma ?laments can be derived from the model of a weighted acoustic line source, consisting of elementary point sources with N-shaped excitation.
关键词： acoustic radiation,plasma filament,femtosecond laser,directivity,shock waves
更新于2025-09-12 10:27:22
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Scanning laser terahertz near-field reflection imaging system
摘要： We developed a scanning laser terahertz (THz) near-field reflection imaging system using a fiber-coupled femtosecond laser source for high spatial resolution measurements without any sub-wavelength probes. In this system, THz wave pulses generated at the laser focusing spot in a non-linear optical crystal interact with a sample set on the crystal. Using this system, we obtained the THz reflection images of metallic structures with a resolution of ～λTHz/34 (λTHz = 680 μm) and also observed paraffin-embedded human breast tissue of several 10 μm in size. These results promise that this system can be suitable for industrial applications which require micron-scale resolution.
关键词： near-field,terahertz,reflection imaging,femtosecond laser,high spatial resolution
更新于2025-09-12 10:27:22
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Spectral dependencies of terahertz emission from femtosecond laser excited surfaces of germanium crystals
摘要： Pulsed terahertz emission excitation spectra from germanium crystals are being presented. The most intense terahertz pulses from germanium crystals are emitted at quanta energies coinciding with technologically significant telecommunication wavelengths. The terahertz generation mechanisms are an interplay of the photocurrent surge in the surface electric field and the photo-Dember effect. Remarkably, the terahertz emission is also observed at quanta energies below the direct bandgap of this material even when photoexcited at a surface normal. This is the result of a broken symmetry of effective electron mass in the L valleys.
关键词： photo-Dember effect,terahertz emission,femtosecond laser,photocurrent surge,germanium crystals
更新于2025-09-12 10:27:22