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Miniaturized Frequency Selective Rasorber with a Wide Transmission Band Using Circular Spiral Resonator
摘要： This paper presents a miniaturized frequency selective rasorber (FSR) that has a wide transmission band with low insertion loss (IL) and a wide absorption band below the transmission band. The FSR is composed of a resistive sheet and a bandpass FSS. The unit cell of the resistive sheet is a resistor-loaded hexagonal metallic loop (HML), each side of which is inserted with a circular spiral resonator (CSR) in the center. The CSR is equivalent to a parallel LC circuit that has a high inductance and low parasitic capacitance. At high frequency of 10 GHz, the CSR resonates to be an infinite impedance, around which a 0.5-dB-transmission band of 8.68-11.34 GHz is produced. The bandpass FSS is a triple-layer FSS in which two layers of identical hexagonal patches are coupled through a layer of hexagonal aperture; it has a fast roll-off 0.5-dB-transmission band of 8.2-11.33 GHz, which almost coincide with that of the resistive sheet. The 1-dB-transmission band of the FSR by placing the resistive sheet on the bandpass FSS is 8.3-11.07 GHz. At low frequency, the FSR performs as an absorber, and the 10-dB-absorption band is 2.4-7.1 GHz. Besides, due to its tiny physical sizes of only 1.2 mm×1.6 mm, the CSR can be viewed as a lumped element circuit with a high inductance, in which the parallel resonance is almost independent to incident angle. The transmission performance of the FSR has a good independence of and polarizations and incident angles. A prototype of the proposed FSR is fabricated and measured to validate the design.
关键词： Frequency-selective rasorber,transmission,absorption,circular spiral resonator
更新于2025-09-10 09:29:36
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Monolithic axial and radial metal-semiconductor nanowire heterostructures
摘要： The electrical and optical properties of low dimensional nanostructures depend critically on size and geometry and may differ distinctly from those of their bulk counterparts. In particular, ultra-thin semiconducting layers as well as nanowires have already proven the feasibility to realize and study quantum size effects enabling novel ultra-scaled devices. Further, plasmonic metal nanostructures attracted recently a lot of attention because of appealing near-field mediated enhancement effects. Thus, combining metal and semiconducting constituents in quasi 1D heterostructures will pave the way for ultra-scaled systems and high-performance devices with exceptional electrical, optical and plasmonic functionality. This paper reports on the sophisticated fabrication and structural properties of axial and radial, Al-Ge and Al-Si nanowire heterostructures, synthesized by a thermally induced exchange reaction of single-crystalline Ge-Si core-shell nanowires and Al pads. This enables a self-aligned metallic contact formation to Ge segments beyond lithographic limitations as well as ultra-thin semiconducting layers wrapped around monocrystalline Al core nanowires. High-resolution transmission electron microscopy, energy dispersive X-ray spectroscopy and μ-Raman measurements proved the composition and perfect crystallinity of these metal-semiconductor nanowire heterostructures. This exemplary selective replacement of Ge by Al represents a general approach for the elaboration of radial and axial metal-semiconductor heterostructures in various Ge-semiconductor heterostructures.
关键词： metal-semiconductor heterostructure,germanium,aluminum,transmission electron microscopy,nanowire
更新于2025-09-10 09:29:36
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Transparent tetragonal-cubic zirconia composite ceramics densified by spark plasma sintering and hot isostatic pressing
摘要： Targeting higher toughness transparent ceramics, tetragonal (3 mol % yttria) and cubic (8 mol % yttria) ZrO2 starting powder mixtures were densified by spark plasma sintering (SPS) in vacuum at 1100°C and post hot isostatic pressing (HIP) in argon at 1100°C. The influence of the ultra-fine microstructure and phase composition on the fracture resistance and light transmission in the visible and infra-red range was assessed. Of special interest was the influence of a thermal annealing step in air on the transparency of the SPS and SPS-HIP ceramics.
关键词： Total Forward Transmission,Hot Isostatic pressing,Spark Plasma Sintering,Ferro-elastic domain switching,Transparent zirconia
更新于2025-09-10 09:29:36
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Supervised Machine Learning Techniques for Quality of Transmission Assessment in Optical Networks
摘要： We propose and compare a number of machine learning models to classify unestablished lightpaths into high or low quality of transmission (QoT) categories in impairment-aware wavelength-routed optical networks. The performance of these models is evaluated in long haul communication networks and compared to previous proposals. Results show that, especially random forests and bagging trees approaches, significantly reduce the required computing time to classify the QoT of a given lightpath, while accuracy remains around 99.9%.
关键词： lightpath,impairment-aware optical networks,machine learning,quality of transmission
更新于2025-09-10 09:29:36
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SiGe-Driven Hybrid-Integrated Silicon Photonic Link Using Optical-Domain Equalization
摘要： We report 50 and 60-Gb/s hybrid-integrated optical links in the O-band with CMOS photonic components driven by feed-forward silicon-germanium equalization. The link includes a segmented-electrode Mach Zehnder modulator and a Ge photodetector that provide high bandwidths and the potential for tight integration with control and monitoring electronics. The combination of these features enable the demonstration of a 60-Gb/s AC-coupled link and a 50-Gb/s DC-coupled link with BERs below 10-12 without the use of forward-error correction codes. This result provides a promising path toward extending speeds in latency sensitive optical links.
关键词： high-speed transmission,photonic integrated circuits,optical interconnects,Feed-forward equalization
更新于2025-09-10 09:29:36
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2018 Atmospheric Transmission Models-Modeling in Remote Sensing Meeting [Conference Reports]
摘要： The 2018 Atmospheric Transmission Models (ATM)–Modeling in Remote Sensing (MIRS) Meeting was held in Newton, Massachusetts, 4–6 June. This was a continuation of the long-running ATM meeting expanded by collaboration with the recently initiated IEEE Geoscience and Remote Sensing Society (GRSS) MIRS Technical Committee (TC). This report provides background on the meeting and the MIRS TC as well as summaries of the meeting presentations.
关键词： atmospheric retrievals,Modeling in Remote Sensing,radiative transfer,MODTRAN,molecular spectroscopy,Atmospheric Transmission Models
更新于2025-09-10 09:29:36
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SCATTERING AND TRANSMISSION OF WAVES IN MULTIPLE RANDOM ROUGH SURFACES: ENERGY CONSERVATION STUDIES WITH THE SECOND ORDER SMALL PERTURBATION METHOD
摘要： Energy conservation is an important consideration in wave scattering and transmission from random rough surfaces and is particularly important in passive microwave remote sensing. In this paper, we study energy conservation in scattering from layered random rough surfaces using the second order small perturbation method (SPM2). SPM2 includes both first order incoherent scattering and a second order correction to the coherent fields. They are combined to compute the total reflected and transmitted powers, as a sum of integrations over wavenumber kx, in which each integration includes the surface power spectra of a rough interface weighted by an emission kernel function (assuming the roughness of each interface is uncorrelated). We calculate the corresponding kernel functions which are the power spectral densities for one-dimensional (1D) surfaces in 2D scattering problems and examine numerical results for the cases of 2 rough interfaces and 51 rough interfaces. Because it is known that the SPM when evaluated to second order conserves energy, and it can be applied to second order for arbitrary surface power spectra, energy conservation can be shown to be satisfied for each value of kx in the kernel functions. The numerical examples show that energy conservation is obeyed for any dielectric contrast, any layer configuration and interface, and arbitrary roughness spectra. The values of reflected or transmitted powers predicted, however, are accurate only to second order in small surface roughness.
关键词： roughness spectra,wave scattering,random rough surfaces,SPM2,transmission,passive microwave remote sensing,layered random rough surfaces,small perturbation method,power spectral densities,Energy conservation,dielectric contrast
更新于2025-09-10 09:29:36
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Heat-Treatment Induced Magnetic Anisotropy of GaMnSb Films
摘要： Conditions and mechanisms of controlled variation of the magnetic anisotropy of GaMnSb films containing magnetic MnSb nanoinclusions by means of heat treatment have been determined. For this purpose, the temperature and magnetic-field dependences of the magnetic moments of samples before and after thermal annealing were measured using a SQUID magnetometer. It is established that the heat treatment of GaMnSb films leads to a significant increase in the values of characteristics determined by the magnetic anisotropy, including the growth of blocking temperature (from 95 to 390 K) and the magnetic anisotropy field (from 330 to 630 Oe). Results of transmission electron microscopy investigation indicate that a change in the magnetic anisotropy of GaMnSb films as a result of their thermal annealing can be related to a transition of the crystalline structure of magnetic MnSb nanoinclusions from hexagonal (space group P62/mmc) to cubic (space group F-43m).
关键词： magnetic anisotropy,GaMnSb films,SQUID magnetometer,transmission electron microscopy,MnSb nanoinclusions,heat treatment
更新于2025-09-10 09:29:36
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Digital Domain Power Division Multiplexed Dual Polarization Coherent Optical OFDM Transmission
摘要： Capacity is the eternal pursuit for communication systems due to the overwhelming demand of bandwidth hungry applications. As the backbone infrastructure of modern communication networks, the optical fiber transmission system undergoes a significant capacity growth over decades by exploiting available physical dimensions (time, frequency, quadrature, polarization and space) of the optical carrier for multiplexing. For each dimension, stringent orthogonality must be guaranteed for perfect separation of independent multiplexed signals. To catch up with the ever-increasing capacity requirement, it is therefore interesting and important to develop new multiplexing methodologies relaxing the orthogonal constraint thus achieving better spectral efficiency and more flexibility of frequency reuse. Inspired by the idea of non-orthogonal multiple access (NOMA) scheme, here we propose a digital domain power division multiplexed (PDM) transmission technology which is fully compatible with current dual polarization (DP) coherent optical communication system. The coherent optical orthogonal frequency division multiplexing (CO-OFDM) modulation has been employed owing to its great superiority on high spectral efficiency, flexible coding, ease of channel estimation and robustness against fiber dispersion. And a PDM-DP-CO-OFDM system has been theoretically and experimentally demonstrated with 100 Gb/s wavelength division multiplexing (WDM) transmission over 1440 km standard single mode fibers (SSMFs).
关键词： spectral efficiency,digital domain power division multiplexing,non-orthogonal multiple access,coherent optical OFDM,optical fiber transmission
更新于2025-09-10 09:29:36
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Direct imaging of Indium-rich triangular nanoprisms self-organized formed at the edges of InGaN/GaN core-shell nanorods
摘要： Higher indium incorporation in self-organized triangular nanoprisms at the edges of InGaN/GaN core-shell nanorods is directly evidenced by spectral cathodoluminescence microscopy in a scanning transmission electron microscope. The nanoprisms are terminated by three 46 nm wide a-plane nanofacets with sharp interfaces forming a well-defined equilateral triangular base in the basal plane. Redshifted InGaN luminescence and brighter Z-contrast are resolved for these structures compared to the InGaN layers on the nanorod sidewalls, which is attributed to at least 4 % higher indium content. Detailed analysis of the inner optical and structural properties reveals luminescence contributions from 417 nm up to 500 nm peak wavelength proving the increasing indium concentration inside the nanoprism towards the nanorod surface.
关键词： cathodoluminescence microscopy,InGaN/GaN core-shell nanorods,nanoprisms,scanning transmission electron microscope,indium incorporation
更新于2025-09-10 09:29:36