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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Hybrid Physical Optics-Ray Tracing Method for the RCS Calculation of Electrically Large Objects Covered with Radar Absorbing Materials
摘要： A hybrid method based on Ray Tracing and Physical Optics for the estimation of the radar cross section of large metallic targets covered with radar absorbing materials is presented. The reflection coefficient of the multilayer structure composed by the metallic layer covered with radar absorbing materials is analytically evaluated through a transmission line model. The accuracy of the Radar Cross Section estimation is validated by full-wave simulations based on the Method of Moments. A corner reflector coated with Radar Absorbing Material (RAM) is used as a test-case of the proposed method. The obtained results exhibit a good agreement if compared against full-wave simulations.
关键词： Physical Optics (PO),Impedance Boundary Condition (IBC),Ray Tracing (RT),Radar Absorbing Material (RAM),Frequency Selective Surface (FSS)
更新于2025-09-04 15:30:14
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Partial Differential Phase Shift Keying – Theory and Motivation
摘要： Recently it was demonstrate that partial Differential Phase Shift Keying (i.e., when the delay inside the Delay Interferometer is shorter than the symbol period) can partially compensate the signal deformation caused by spectrally narrowing the optical channel (by interleavers, add-drop elements, Wavelength Division Multiplexing filters, etc.). In this paper the source of this effect is investigated with numerical simulations and, to the best of our knowledge for the first time, analytically. We found that our analytical analysis matched the simulation results with high accuracy. Furthermore, a phenomenological relation, which relates the optimum Free Spectral Range to the channel bandwidth, was derived.
关键词： Differential Phase Shift Keying,Free Spectral Range,Delay Interferometer,fiber optics
更新于2025-09-04 15:30:14
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Confocal Adaptive Optics Imaging of Peripapillary Nerve Fiber Bundles: Implications for Glaucomatous Damage Seen on Circumpapillary OCT Scans
摘要： To improve our understanding of glaucomatous damage as seen on circumpapillary disc scans obtained with frequency-domain optical coherence tomography (fdOCT), fdOCT scans were compared to images of the peripapillary retinal nerve fiber (RNF) bundles obtained with an adaptive optics-scanning light ophthalmoscope (AO-SLO). The AO-SLO images and fdOCT scans were obtained on 6 eyes of 6 patients with deep arcuate defects (5 points (cid:2)(cid:3)15 db) on 10-2 visual fields. The AO-SLO images were montaged and aligned with the fdOCT images to compare the RNF bundles seen with AO-SLO to the RNF layer thickness measured with fdOCT. All 6 eyes had an abnormally thin (1% confidence limit) RNF layer (RNFL) on regions of RNF bundles on AO-SLO in fdOCT and abnormal corresponding regions. However, regions of abnormal, but equal, RNFL thickness on fdOCT scans varied in appearance on AO-SLO images. These regions could be largely devoid of RNF bundles (5 eyes), have abnormal-appearing bundles of lower contrast (6 eyes), or have isolated areas with a few relatively normal-appearing bundles (2 eyes). There also were local variations in reflectivity of the fdOCT RNFL that corresponded to the variations in AO-SLO RNF bundle appearance. Relatively similar 10-2 defects with similar fdOCT RNFL thickness profiles can have very different degrees of RNF bundle damage as seen on fdOCT and AO-SLO. While the results point to limitations of fdOCT RNFL thickness as typically analyzed, they also illustrate the potential for improving fdOCT by attending to variations in local intensity.
关键词： optical coherence tomography,retinal nerve fiber layer,glaucoma,adaptive optics,optic disc
更新于2025-09-04 15:30:14
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Voltaire e Algarotti: divulgadores da óptica de Newton na Europa do século XVIII
摘要： In the beginning of 18th century, Newton published his main work about light and colors, the Opticks. Impregnated by an inductive perspective, the book became the major reference for the studies about light and colors, being widely popularized by Newton’s followers. In this article, we analyze how two important works contributed to this process of popularization and also what image of science they intended to propagate: Voltaire’s Elements of Newton’s philosophie and Algarotti’s Sir Isaac Newton’s philosophy explain’d for the use of the ladies. We will be notice that both authors distorted the content of the Opticks, in order to propagate an idealized image of Newtonian ideas and natural philosophy itself.
关键词： Optics,Voltaire,Newton,Algarotti,Popularization of science,18th century
更新于2025-09-04 15:30:14
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Fourier Optics of Fractal Structures
摘要： The scaling characteristics of Fourier spectra of fractal structures are determined. Their stability and influence on cognitive processes associated in particular with the aesthetic aspects of perceiving objects with self-similarity criteria are estimated. Evidence of their heuristic importance for Fourier analysis results is presented using an example in which the properties of aperiodic multilayer structures and chaotic processes are considered.
关键词： scaling characteristics,fractal structures,aperiodic multilayer structures,Fourier optics,cognitive processes,chaotic processes
更新于2025-09-04 15:30:14
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Zinc(II) as a Versatile Template for Efficient Dipolar and Octupolar Second-Order Nonlinear Optical Molecular Materials §
摘要： This short review outlines the main results obtained in the field of molecular materials based on zinc coordination compounds for second-order nonlinear optics. It presents an overview of the main classes of second-order nonlinear optical (NLO) active complexes bearing monodentate, bidentate, tridentate, or tetradentate π-delocalized ligands such as substituted stilbazoles, bipyridines, phenanthrolines, terpyridines, and Schiff bases. Macrocyclic ligands such as porphyrins and phthalocyanines are not covered. This paper shows how coordination to the Zn(II) center of π-delocalized nitrogen donor ligands produces a significant enhancement of their quadratic hyperpolarizability. Dipolar complexes are mainly presented, but octupolar zinc complexes are also presented. The coverage is mainly focused on NLO properties that are measured at the molecular level, working in solution, by means of the electric field-induced second harmonic generation (EFISH) or the hyper-Rayleigh scattering (HRS) techniques.
关键词： Zinc(II) complexes,EFISH,second-order nonlinear optics,HRS
更新于2025-09-04 15:30:14
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Layered Hybrid Perovskites for Highly Efficient Three-Photon Absorbers: Theory and Experimental Observation
摘要： Multiphoton absorption may find many technological applications, such as enhancing the conversion efficiency of solar cells by the utilization of sub-band-energy photons, below-bandgap photodetection through the simultaneous absorption of several infrared photons for photocurrent generation, or light frequency upconversion for high-resolution, 3D imaging. To enhance multiphoton absorption in semiconducting materials, one of the strategies is to explore low-dimensional excitons. Here, a quantum perturbation theory on a giant enhancement in three-photon absorption (3PA) arising from 2D excitons in multilayered crystals of organic–inorganic hybrid perovskites is presented. The maximal 3PA coefficient is predicted to be in the range of 2–7 cm3 GW?2 at 1100 nm, the largest values reported so far for any 2D and bulk semiconductors at room temperature. Excellent agreement between theory and the experimental findings unambiguously demonstrates a pivotal role in the enhancement of 3PA played by 2D excitons. The theory predicts that the resonant 3PA coefficient should be enhanced further by at least two orders of magnitude with very low temperature. The findings are essential for understanding giant 3PA arising from 2D excitons in layered hybrid perovskites and may open new pathways for highly efficient conversion from infrared light energy to either electrical energy or higher-frequency light emission/lasing.
关键词： nonlinear optics,three-photon absorbers,2D excitons,hybrid perovskites
更新于2025-09-04 15:30:14
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DESIGN OF A PYRAMIDAL HORN ANTENNA WITH LOW E-PLANE SIDELOBES USING TRANSFORMATION OPTICS
摘要： Transformation optics is a convenient way to control the pattern of electromagnetic ?elds. In this paper, using a novel transformation, we propose the design procedure of a horn antenna having low backlobe and sidelobe levels in its E-plane. By applying conformal transformation, the rectangular horn proposed in this paper can be realized with isotropic materials. This proposed antenna can be easily implemented by both ordinary dielectric materials and isotropic graded refractive index (GRIN) materials. In the ?rst proposed design, in addition to the isotropy, homogeneity is furthermore introduced into the horn, and only four kinds of isotropic materials are required throughout. In the second design, it is demonstrated that the designed structure can also be implemented by graded photonic crystals (GPCs) operating in metamaterial regime. They have low loss as well as broad frequency band and are easy to implement. Simulation results are presented to validate the design approach.
关键词： low sidelobes,horn antenna,graded refractive index,graded photonic crystals,Transformation optics,isotropic materials,conformal transformation
更新于2025-09-04 15:30:14
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Illusion Optics: Disguising with Ordinary Dielectric Materials
摘要： Illusion devices are usually designed using transformation optics. Here, a new method is proposed to achieve optical illusions without external devices by elaborately manipulating the scattering potential of an object. In contrast to the conventional transformation optics method, which completely replaces one object by the image of another object using complementary\restoring media and a superlens, the method described here is more of a cosmetic operation for an object, which modifies the scattering pattern of the object to mimic another object by exchanging their scattering potentials in two symmetrical areas in the wave vector domain. Only positive isotropic non-magnetic materials are introduced in the present method, which is impossible using the conventional method because superlenses require negative-index materials. Both numerical simulations and experimental demonstrations are used to verify the performance of the illusion devices of this method.
关键词： scattering potential,wave vector domains,illusion optics,isotropic dielectric materials
更新于2025-09-04 15:30:14
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First Hyperpolarizability of 1,3-Thiazolium-5-Thiolates Mesoionic Compounds
摘要： The first hyperpolarizabilities of the mesoionic compounds (MICs) 2-(4-chlorophenyl)-3-methyl-4-phenyl-1,3-thiazole-5-thiolate (MIC-1), 2-(4-chlorophenyl)-3-methyl-4-(4-methylphenyl)-1,3-thiazole-5-thiolate (MIC-2), and (2-(4-chlorophenyl)-3-methyl-4-(4-methoxyphenyl)-1,3-thiazole-5-thiolate) (MIC-3), dissolved in dimethyl sulfoxide (DMSO), are reported here for the first time to our knowledge. Hyper-Rayleigh scattering experiments were performed with an excitation source operating at ?? =1180 nm (?? = 8475 cm?1). The measured hyperpolarizability, ??(2??), was used to calculate the static hyperpolarizability, ??(0), by applying the classical two-level model. The values obtained for ??(0) were 10.1 × 10?30 esu (MIC-1), 8.7 × 10?30 esu (MIC-2) and 10.4 × 10?30 esu (MIC-3) which are smaller than previous theoretical predictions that did not consider features related to the liquid phase.
关键词： nonlinear optics,Hyper-Rayleigh scattering,mesoionic compounds,hyperpolarizability,DMSO
更新于2025-09-04 15:30:14