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Dispersion flattened extremely high-birefringent kagome lattice elliptic core photonic crystal fiber in THz regime
摘要： A highly birefringent elliptic porous-core photonic crystal fiber with kagome lattice cladding has been presented for terahertz (THz) wave transmission. The slotted airholes inside the elliptic core effectively disrupt the symmetry of the porous-core which offers extremely high modal birefringence whereas the kagome cladding structure results in significantly low effective material loss (EML). The birefringence of the proposed structure is 9.73 × 10?2 for y-polarized mode at an operating frequency of 1 THz. The suggested structure also provides very flat dispersion over a bandwidth of 300 GHz. It is highly expected that this elliptic core waveguide would be remarkably useful in numerous polarization maintaining THz applications.
关键词： Photonic crystal fibers,Microstructured fibers,Fibres, polarization-maintaining,Optical communications,Fiber design and fabrication
更新于2025-09-23 15:23:52
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Maskless Arrayed Nanofiber Mats by Bipolar Pyroelectrospinning
摘要： The numerous advantages of micro and nanostructures produced by electrospinning (ES) have stimulated enormous interest in this technology with potential application in several fields. However, ES has still some limitations in controlling the geometrical arrangement of the fibre mats so that expensive and time-consuming technologies are usually employed for producing ordered geometries. Here we present a technique that we call 'bipolar pyro-electrospinning' (b-PES) for generating ordered-arrays of fibre mats in a direct manner by using the bipolar pyroelectric field produced by a periodically poled lithium niobate crystal (PPLN). The b-PES is free from expensive electrodes, nozzles and masks because it makes use simply of the structured pyroelectric field produced by the PPLN crystal used as collector. The results show clearly the reliability of the technique in producing a wide variety of arrayed fibre mats that could find application in bioengineering or many others field. Preliminary results of live cells patterning under controlled geometrical constraints is also reported and discussed in order to show potential exploitation as scaffold in tissue engineering.
关键词： PDLLA,pyro-electrospinning,arrayed mats,pyroelectric effect,polymer fibres
更新于2025-09-23 15:22:29
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Optical matching of a multimode gradient fibre and single-mode stepped-index fibre in a photopolymerizable composition
摘要： The opportunity to optically match waveguides characterized by an essentially different field structure in a photopolymerizable medium is investigated. The example of a multimode gradient fibre (core diameter 50 μm) and a single-mode stepped-index fibre SMF-28 (core diameter 8.2 μm) shows that the efficiency of radiation transmission from the wide fibre into the narrow one can reach 60% at a distance between their end faces of about 900 μm.
关键词： nonlinear optics,photopolymer,optical matching of fibres,fibre optics,laser radiation
更新于2025-09-23 15:22:29
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Corneal Confocal Microscopy detects a Reduction in Corneal Endothelial Cells and Nerve Fibres in Patients with Acute Ischemic Stroke
摘要： Endothelial dysfunction and damage underlie cerebrovascular disease and ischemic stroke. We undertook corneal confocal microscopy (CCM) to quantify corneal endothelial cell and nerve morphology in 146 patients with an acute ischemic stroke and 18 age-matched healthy control participants. Corneal endothelial cell density was lower (P < 0.001) and endothelial cell area (P < 0.001) and perimeter (P < 0.001) were higher, whilst corneal nerve fibre density (P < 0.001), corneal nerve branch density (P < 0.001) and corneal nerve fibre length (P = 0.001) were lower in patients with acute ischemic stroke compared to controls. Corneal endothelial cell density, cell area and cell perimeter correlated with corneal nerve fiber density (P = 0.033, P = 0.014, P = 0.011) and length (P = 0.017, P = 0.013, P = 0.008), respectively. Multiple linear regression analysis showed a significant independent association between corneal endothelial cell density, area and perimeter with acute ischemic stroke and triglycerides. CCM is a rapid non-invasive ophthalmic imaging technique, which could be used to identify patients at risk of acute ischemic stroke.
关键词： Corneal Confocal Microscopy,corneal endothelial cells,acute ischemic stroke,corneal nerve fibres
更新于2025-09-23 15:21:21
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Characterization of monolithic GAGG:Ce coupled to both PMT and SiPM array for gamma imaging in Nuclear Medicine
摘要： GaGG:Ce scintillation crystal is very useful for nuclear imaging purposes, thanks to its several advantages (high density, short decay time, high light yield and good energy resolution, no self-activity, no hygroscopic). However, only the recent improvements in the growth processes make it available with large size, in order to use it in monolithic configuration. The main drawbacks of pixelated crystals, as non-uniform response, high production costs and optical light loss, could be therefore overcome. In this work the characterization of this promising crystal coupled both to a single channel PMT (spectrometric purpose) and to a new technology SiPM (50% PDE and 74% geometrical fill factor) has been performed. The detection efficiency results good both for SPECT (87% at 122 keV) and for PET (18% at 356 keV) applications. However, the unexpected result arises from the energy resolution: at 356 keV 8.9% and 8.0% for single channel PMT and SiPM configuration, respectively. In other terms, the used SiPM allows to achieve higher energy resolution than single channel PMT. Moreover, a high imaging performance has been observed, with a millimeter intrinsic spatial resolution.
关键词： SPECT,PET PET/CT,Gamma camera,Intra-operative probes,Scintillators and scintillating fibres and light guides,coronary CT angiography (CTA),Scintigraphy and whole-body imaging
更新于2025-09-23 15:21:01
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Fabrication of Gratings in Mid-Infrared Compatible Fibres via Femtosecond Laser Direct Inscription
摘要： We report on research into the fabrication of different types of gratings into optical fibres that are transparent at mid-infrared wavelengths. In particular, we focus on direct femtosecond laser inscription of fibre-Bragg gratings with parallel as well as with tilted grating planes into zirconium and indium fluoride fibres. It is shown that post-annealing of the gratings can lead to an increase or decrease in reflectivity depending on the fabrication method and that even a relatively low concentration of rare-earth ions that are present in active fibres can have a big influence on the inscription process. Further, the feasibility investigating the physical mechanisms that underpin the induced refractive index modulation by utilising argon-beam cross-sectional polishing of the inscribed fibres followed by spatially resolved Raman microscopy and electron probe microanalysis, is discussed.
关键词： tilted fibre Bragg gratings,femtosecond-laser inscription,mid-infrared fibres,fluoride fibres,fibre Bragg gratings
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) - Optimisation of Dispersion Flatness in Nanostructured Core Fibres
摘要： Nanostructured optical fibres allow to obtain an arbitrary profile of refraction index in the core. These fibres are composed of several thousands of rods with diameter smaller than incident wavelength. Their optical performance is described with the Maxwell-Garnett effective medium theory. A modification of nanorods distribution or doping level in nanorods allow controlling of chromatic dispersion, polarization and modal properties of the nanostructured fibres. We study an influence of additional microrings in the core on fibre dispersion characteristics. We consider a fibre composed of pure silica nanorods and silica nanorods highly doped with Ge (concentration of GeO2 equals 20% mol). Modification of core internal structure affects electric field distribution in the fundamental mode, and consequently results in changes of its dispersion characteristics. We show that flat, all-normal dispersion characteristics (≈ 2.5 ps/nm/km) in wavelength range from 1.3 up to 2.15 μm can be achieved in the optimized structure. Moreover, within these limits, 1.5 μm to 1.9 μm range was revealed to be ultra-flat (≈ 0.2 ps/nm/km). In contrast to already reported in the literature similar fibres, proposed design is based on fused silica glasses, exhibits spectrally broader and more flat dispersion profile, it is an all-solid construction and it has the effective mode area equal 13μm2 for λ=1.55μm wavelength. Thanks to such characteristics, the fiber allows free from higher order distortions light propagation of highly confined broadband optical pulses, what might find applications in ultrafast optics, or dispersion management systems.
关键词： ultrafast optics,Maxwell-Garnett effective medium theory,chromatic dispersion,nanostructured optical fibres,all-normal dispersion
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) - Lasing and Gain Properties of Multicomponent Optical Fibers with Heavily Er-Doped Phosphate Core and Silica Cladding
摘要： The most common Er-doped fibres being used today are silica-based. However solubility limit of erbium ions in silica glass restrict shortening of the gain medium in fibre light sources and that way, it limits improving single-frequency fibre lasers, amplifiers and pulsed fibre lasers characteristics. Shortening of a fibre gain medium might be successfully realised by using high-concentration Er-doped phosphate glasses. It was shown that such type of glass allows getting rare-earth ions concentration an order of magnitude higher in comparison with silica glasses without ions clusterization [1]. But significant drawbacks of phosphate fibres are their low corrosion resistance and high losses of its fusion splices with standard silica fibres [2]. The main purpose of our work was an investigation of fibre light sources based on novel multicomponent fibre with 3wt.% Er-doped phosphate core and silica cladding, which take advantages of both phosphate and silica glasses.
关键词： phosphate core,Er-doped fibres,silica cladding,multicomponent fibre,fibre light sources
更新于2025-09-16 10:30:52
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Comparaison in vitro des flux de bulles avec le Laser Thulium Fibré Superpulsé selon le diamètre de fibre laser (150 μm vs 272 μm) et le milieu d’activation (sérum physiologique, produit de contraste iodé, eau pour préparation injectable, urine)
摘要： Le Laser Thulium Fibré (TFL) représente une alternative au laser Holmium:YAG pour la lithotritie endocorporelle, permettant d’utiliser des fibres laser (FL) de diamètres inférieurs à 200 μm. L’objectif était de comparer in vitro les dimensions et durée des flux de bulles (FB) entre FL de diamètre 272 μm (272CDF) et 150 μm (150CDF) avec le TFL selon le milieu d’activation.
关键词： lithotritie endocorporelle,Laser Thulium Fibré,flux de bulles,fibres laser
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) - On the Possibility of Structural Characterisation of Hollow Core Fibres using Whispering Gallery Modes Excited by Laser and Broadband Light
摘要： Significant progress has been made in recent years in driving down the loss of hollow core fibres (HCFs), such as photonic bandgap fibres (PBGF), antiresonant nodeless fibres (ANF), and nested antiresonant nodeless fibres (NANF) towards that of their conventional solid single mode counterparts. In order to achieve the ultimate performance of HCFs, an accurate control of the dimensions and symmetry of the internal constituent elements is key in both the assembled preforms and drawn canes and fibres. Non-destructive optical methods to monitor and assess the internal features of HCFs over the entire fabrication process are therefore of great interest. Previously, morphology dependent resonances [1] and whispering gallery modes (WGMs) [2], excited by side illumination of the fibre, have been used to enable the precise measurement of cladding diameter variations with an accuracy greater than that of competing interferometric approaches. Motivated by this earlier work we have started studies into the opportunities provided by side illumination of HCF canes and fibres being drawn, and report some of our initial observations, which we hope will ultimately provide useful information on the internal features of HCFs.
关键词： whispering gallery modes,nested antiresonant nodeless fibres,hollow core fibres,photonic bandgap fibres,antiresonant nodeless fibres
更新于2025-09-12 10:27:22