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oe1(光电查) - 科学论文

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出版时间
  • 2020
研究主题
  • fast processes in solids
  • femtosecond interferometry
  • femtosecond laser radiation
应用领域
  • Optoelectronic Information Science and Engineering
机构单位
  • Prokhorov General Physics Institute, Russian Academy of Sciences; National Research Nuclear University MEPhI
441 条数据
?? 中文（中国） ▾

  • Insights into Ultrashort Laser-Driven Au:TiO <sub/>2</sub> Nanocomposite Formation

    摘要： Modern methods of laser-based nanocomposite fabrication and treatment rely on a deep understanding of the interplay between a set of mechanisms involved, such as nanoparticle growth and decay, material phase transformation, degradation and damage. In this work, scanning multi-pulse femtosecond laser irradiation is used for Au : T iO2 nanocomposite formation. Depending on laser scan speed two di?erent regimes are observed revealing di?erent gold nanoparticle growth rates. The regime of the remarkably fast laser-induced growth of Au nanoparticles is found to be accompanied by the cavity formation in titania ?lm around the particles. The transition between two formation regimes is found to be abrupt con?rming the catastrophic mechanism of Au nanoparticle growth. The obtained results are analyzed based on the developed numerical model including e?ects such as nanoparticle absorption, local ?eld enhancement, photo-induced free carrier generation, plasmon-assisted electron emission, and thermal heat transfer from nanoparticles towards titania matrix. Our modeling reveals the crucial role of collective thermoplasmonic e?ects caused namely by bimodal nanoparticle size distribution. The performed analysis also suggests that spall in solid state is responsible for ?nal matrix degradation if nanoparticles become large enough. The considered laser-based formation of optical nanocomposites is crucial not only for the better understanding of ultra-short laser interactions with glass-metallic nanocomposite materials, but also for numerous applications in photocatalysts, solar cells, and chemo-sensors.

    关键词： femtosecond laser,nanocomposite,thermoplasmonic effects,nanoparticle growth,Au:TiO2

    更新于2025-09-23 15:19:57

  • Femtosecond Laser-assisted Preparation of Conjunctival Autograft for Pterygium Surgery

    摘要： Femtosecond laser-assisted conjunctival autografts (CAG) preparation was recently proposed. This study reports the outcomes of the first clinical trial on the use of laser to prepare CAG in pterygium surgery, and to compare the outcomes with those of manual technique. Forty eyes undergoing primary pterygium excision with laser-assisted CAG transplantation were prospectively included (L group). Two historical matched cohorts whose cAGs were prepared manually were compared (n = 78 eyes by the same experienced surgeon, M group; n = 78 eyes by trainees; TM group). We found the laser-created CAGs had only 11 μm deviation from the targeted thickness. The best-corrected visual acuity improved, and the astigmatism significantly decreased after surgery, with comparable efficacy across 3 groups. The 1-year recurrence rate was 2.5%, 3.8% and 7.7% in the L, M and TM groups, respectively (P = 0.12). There was no significant difference between the L and M groups in the complication rate (5.0% and 1.3%, respectively), surgical time (19.4 ± 5.1 and 19.1 ± 6.2 minutes, respectively), and postoperative discomfort scores (0.1 ± 0.3 and 0.2 ± 0.3, respectively), but these outcomes were significantly less favorable in the TM group. The results of this first comparative clinical trial suggest that femtosecond laser-assisted CAG preparation can be considered as an alternative technique for CAGs preparation.

    关键词： femtosecond laser,conjunctival autograft,recurrence rate,clinical trial,pterygium surgery

    更新于2025-09-23 15:19:57

  • Interference microscopy study of the preplasma formed on an iron target surface exposed to high-power femtosecond laser pulses

    摘要： The characteristic scale of spread of the plasma formed on the surface of a bulk iron target irradiated by a femtosecond laser pulse with an intensity of 1016 W cm–2 is measured by time-resolved interference microscopy using femtosecond pulses emitted by a Cr : forsterite laser system with an intensity contrast of 107. The chosen technique is demonstrated to be efficient in such measurements. It is shown experimentally that, as a result of laser pulse impact, the displacement of a plasma layer with a density exceeding critical does not exceed 30 nm.

    关键词： interference microscopy,femtosecond pulse,electron acceleration mechanisms,hot electrons

    更新于2025-09-23 15:19:57

  • Microvascular changes in macula and optic nerve head after femtosecond laser-assisted LASIK: an optical coherence tomography angiography study

    摘要： To measure the microcirculation change of macula and optic nerve head before and after femtosecond laser assisted laser in situ keratomileusis. In total 45 eyes from 45 subjects, who underwent FS-LASIK during June 2017 to December 2017 in Guangdong Provincial People’s Hospital, were recruited in this study. Vessel density in macula and optic nerve head were measured by optical coherence tomography angiography before and after transient elevation in intraocular pressure caused by application of suction ring during surgery. Vessel density (VD) at superficial (SCP) plexus of macular region did not differ after surgery (F(3,132) = 1.41, P = 0.24), while the deep (DCP) plexus of macular region significantly decreased 1 day after surgery (P = 0.001) but returned to its baseline value 1 month postoperatively (P = 0.1). Vessel density of optic nerve head region had no significant changes after surgery (F(2.51,95.18) = 0.6, P = 0.59). A short-term temporary decrease of vessel density at deep layer of macular region was observed in eyes undergoing FS-LASIK. However, the retinal capillary density went back to preoperative level 1 month after surgery. Therefore, transient IOP spike during FS-LASIK did not cause long-term decline of retinal microcirculation.

    关键词： Optical coherence tomography angiography,Femtosecond laser-assisted LASIK,Microvascular changes,Macula,Optic nerve head

    更新于2025-09-23 15:19:57

  • Direct Ultraviolet Laser-Induced Reduction of Disulfide Bonds in Insulin and Vasopressin

    摘要： Ultraviolet (UV) light has been shown to induce reduction of disulfide bonds in solution. The photoreduction is proposed to be a result of electron donation from excited Tyr or Trp residues. In this work, a powerful UV femtosecond laser was used to generate photoreduced products, while the hypothesis of Tyr/Trp mediation was studied with spectroscopy and mass spectrometry. With limited irradiation times of 3 min or less at 280 nm, the laser-induced reduction in arginine vasopressin and human insulin led to significant yields of ～3% stable reduced product. The photogenerated thiols required acidic pH for stabilization, while neutral pH primarily caused scrambling and trisulfide formation. Interestingly, there was no direct evidence that Tyr/Trp mediation was a required criterion for the photoreduction of disulfide bonds. Intermolecular electron transfer remained a possibility for insulin but was ruled out for vasopressin. We propose that an additional mechanism should be increasingly considered in UV light-induced reduction of disulfide bonds in solution, in which a single UV photon is directly absorbed by the disulfide bond.

    关键词： mass spectrometry,photoreduction,disulfide bonds,Tyr/Trp mediation,femtosecond laser,Ultraviolet light

    更新于2025-09-23 15:19:57

  • Qualitative and Quantitative Distinction of <i>ortho</i> -, <i>meta</i> -, and <i>para</i> -Fluorotoluene by Means of Chirped Femtosecond Laser Ionization

    摘要： Femtosecond-laser ionization mass spectrometry (fs-LIMS) is demonstrated to be a powerful analytical method providing access to the qualitative distinction of structural isomers of ortho-, meta-, and para-fluorotoluene. The key point of the approach presented is a systematic variation of the spectral phase of the fs-laser pulses, which characteristically affects the fragmentation pattern observed in the mass spectra. Variation of the linear chirp parameter is also helpful for rationalizing the fragmentation mechanism. Ultimately two ternary mixtures of the three title isomers are quantitatively analyzed in situ with an accuracy of 5% for the molar fractions.

    关键词： structural isomers,Femtosecond-laser ionization mass spectrometry,fragmentation pattern,spectral phase,quantitative analysis,fluorotoluene

    更新于2025-09-23 15:19:57

  • The binding energy of biexcitons in alloy ZnxCd1a??xS quantum dots detected by femtosecond laser spectroscopy

    摘要： Biexcitons localized at ZnxCd1?xS quantum dots (x = 0.37 or 0.45) with a diameter of ~ 45?? synthesized by two different methods were studied by femtosecond laser spectroscopy. The spectral features of ultrafast transient absorption spectra at the short-time delay of 70?fs are associated with the three lowest energy transitions of quantum dots. The shapes of the transient absorption bands were modeled by fitting to linear absorption. The spectral positions of the absorption components of the excited state in the transient spectra take into account the energy of the biexciton coupling. By fitting the experimental transient absorption spectra of ZnxCd1?xS QDs, the binding energies of biexcitons were determined. The biexciton binding energies vary from 16.6 to 37?meV depending on the biexciton transition excited at the ZnxCd1?xS quantum dot.

    关键词： ZnxCd1?xS,Biexciton,Quantum dots,Femtosecond spectroscopy

    更新于2025-09-23 15:19:57

  • Femtosecond Red and Near-Infrared Lasers Due to Cascaded-Raman-Assisted Four-Wave Mixing in a Nonlinear Yb-Doped Fiber Amplifier

    摘要： We demonstrated a straightforward approach to generate red and near-infrared laser emissions by a Raman-assisted four wave mixing (FWM) process in a nonlinear Yb-doped fiber amplifier, delivering 342 fs pulses of 241 nJ at 864 nm, 834 fs pulses of 21 nJ at 751 nm, and 1.9 ps pulses of 3.8 μJ at 1030 nm. A pair of gratings was employed as the pre-compressor to promote the intensity of the fundamental wave in the main amplifier. Multiple wavelengths from 751 to 1273 nm resulted due to cascaded-Raman-assisted FWM. The pre-compression also underlay the achievement of 25.1, 701, and 2000 kW peak power for the red (751 nm), near-infrared (864 nm), and fundamental (1030 nm) components respectively, which restrained the gain narrowing effect during the amplification. It finally led to shorter pulse duration under increased power.

    关键词： femtosecond fiber laser,four-wave mixing,fiber amplifier

    更新于2025-09-23 15:19:57

  • Femtosecond Laser Additive Manufacturing of Multi-Material Layered Structures

    摘要： Laser additive manufacturing (LAM) of a multi-material multi-layer structure was investigated using femtosecond fiber lasers. A thin layer of yttria-stabilized zirconia (YSZ) and a Ni–YSZ layer were additively manufactured to form the electrolyte and anode support of a solid oxide fuel cell (SOFC). A lanthanum strontium manganite (LSM) layer was then added to form a basic three layer cell. This single step process eliminates the need for binders and post treatment. Parameters including laser power, scan speed, scan pattern, and hatching space were systematically evaluated to obtain optimal density and porosity. This is the first report to build a complete and functional fuel cell by using the LAM approach.

    关键词： femtosecond laser,laser,fuel cell,additive manufacturing,fiber laser,YSZ,SOFC

    更新于2025-09-23 15:19:57

  • Investigation of a Bragg Grating-Based Fabrya??Perot Structure Inscribed Using Femtosecond Laser Micromachining in an Adiabatic Fiber Taper

    摘要： This paper presents the fabrication of a fiber Bragg grating (FBG)-based Fabry–Perot (FP) structure (7 mm total length) in an adiabatic fiber taper, investigates its strain and temperature characteristics, and compares the sensing characteristics with a standard polyimide coated FBG sensor. Firstly, a simulation of the said structure is presented, followed by the fabrication of an adiabatic fiber taper having the outer diameter reduced to 70 μm (core diameter to 4.7 μm). Next, the sensing structure, composed of two identical uniform FBG spaced apart by a small gap, is directly inscribed point-by-point using infrared femtosecond laser (fs-laser) micromachining. Lastly, the strain and temperature behavior for a range up to 3400 με and 225 ?C, respectively, are investigated for the fabricated sensor and the FBG, and compared. The fabricated sensor attains a higher strain sensitivity (2.32 pm/με) than the FBG (0.73 pm/με), while both the sensors experience similar sensitivity to temperature (8.85 pm/?C). The potential applications of such sensors include continuous health monitoring where precise strain detection is required.

    关键词： Fabry–Perot,microfiber sensor structure,direct writing,sensor for structural health monitoring,point-by-point fabrication,femtosecond laser micromachining,harsh environment fiber sensor

    更新于2025-09-23 15:19:57