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- 2018
- GaN HEMTs
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- distribution of the complex current at the antenna
- broadband antenna
- standing wave voltage factor
- antenna gain factor
- Electronic Science and Technology
- Oles Honchar Dnipro National University
- University of Tehran
- Gdansk University of Technology
- V. N. Karazin Kharkiv National University
- Reykjavik University
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Broadband Functional Metasurfaces: Achieving Nonlinear Phase Generation toward Achromatic Surface Cloaking and Lensing
摘要： Broadband Functional Metasurfaces: Achieving Nonlinear Phase Generation toward Achromatic Surface Cloaking and Lensing. Generalized law of refraction and reflection has enabled a tremendous amount of degrees of freedom for full vectorial electromagnetic manipulation with metasurfaces. However, owing to the fundamental limitations of bandwidth and efficiency, the implementation of such principle is still far from perfect as truly achromatic efficient wavefront manipulation has not been realized. Here, a design principle based on the generalized Gires–Tournois interference model and catenary electromagnetics theory is proposed that can achieve desired broadband dispersion engineering regardless of the incident polarizations. As a proof of concept, a surface cloak is fabricated and demonstrated with a large fractional bandwidth of more than 40%. An achromatic lens antenna is also designed with focal shift deviation ratio less than 2% across X band to Ku band. Both of the devices show great advances versus traditional approaches by at least one order of magnitude. Besides, this conceptually new design is also applicable to other scenarios, such as beam splitters, vortex beam generators, or metasurface holograms. Considering their compact profiles and simple topologies, it is believed that such functional metasurfaces are promising in practical applications such as beam control, camouflage, and space communications.
关键词： Gires–Tournois interference,achromatic antennas,surface cloaks,functional metasurfaces,broadband dispersion engineering
更新于2025-09-23 15:22:29
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Silicon-compatible fabrication of inverse woodpile photonic crystals with a complete band gap
摘要： Three-dimensional (3D) photonic crystals can provide access to very interesting and unique properties for ultimate control and manipulation of photons, not possible otherwise. However, widespread implementation of such photonic crystals remains elusive because the fabrication technology available today has either silicon (Si) incompatibility, poor scalability, a large number of undesired defects, challenging or impossible placement of intentional defects, or has advanced non-standard process steps available only in a few laboratories. In this work, a new methodology of fabricating 3D photonic crystals free of unintentional defects is developed. This methodology is 'truly' Si-compatible and uses techniques available in any standard fabrication facility. A broadband omnidirectional reflector on Si is demonstrated using the same method. Introduction of intentional defect sites for fabrication of 3D waveguides and optical cavities is also discussed.
关键词： Photonic Crystal,Woodpile,Broadband reflector,Band gap,Empty-space-in-Silicon
更新于2025-09-23 15:22:29
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High-performance Raman quantum memory with optimal control in room temperature atoms
摘要： Quantum memories are essential for quantum information processing. Techniques have been developed for quantum memory based on atomic ensembles. The atomic memories through optical resonance usually suffer from the narrow-band limitation. The far off-resonant Raman process is a promising candidate for atomic memories due to broad bandwidths and high speeds. However, to date, the low memory efficiency remains an unsolved bottleneck. Here, we demonstrate a high-performance atomic Raman memory in 87Rb vapour with the development of an optimal control technique. A memory efficiency of above 82.0% for 6 ns~20 ns optical pulses is achieved. In particular, an unconditional fidelity of up to 98.0%, significantly exceeding the no-cloning limit, is obtained with the tomography reconstruction for a single-photon level coherent input. Our work marks an important advance of atomic memory towards practical applications in quantum information processing.
关键词： room temperature atoms,broadband,optimal control,Raman quantum memory,high efficiency,high fidelity
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - Chengdu (2018.3.26-2018.3.28)] 2018 IEEE International Conference on Computational Electromagnetics (ICCEM) - A Broadband Tri-Polarization Reconfigurable Magneto-Electric Dipole Antenna
摘要： A broadband tri-polarization reconfigurable magneto-electric dipole antenna is presented in this paper. This proposed antenna structure mainly consists of a conventional ME antenna fed by a Γ-probe, four parasitic patches, a rectangular ground plane and four PIN diodes including their corresponding bias circuit. The size of the rectangular ground plane is of 250×180 mm2 and its profile is of 50 mm. Each of the four PIN diodes is controlled by its corresponding bias circuit independently. The proposed antenna is capable of providing three different polarization states including one linear polarized operation mode and two orthogonal circular polarized modes. The simulated overlapped bandwidth (S11≤-10 dB) is about 59% (1.36 GHz~2.5 GHz) for the one linear polarized mode and 78.7% (1.07 GHz~2.46 GHz) for the two orthogonal CP modes. In additional, the simulated overlapped 3-dB AR bandwidth is about 37.2% from 1.2 GHz to 1.75GHz. Detailed design considerations of the proposed antenna are described in the following sections.
关键词： reconfigurable antenna,broadband antenna,magneto-electric antenna,tri-polarization
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE 15th International Conference on Group IV Photonics (GFP) - Cancun (2018.8.29-2018.8.31)] 2018 IEEE 15th International Conference on Group IV Photonics (GFP) - Optimization of a Polarization Beam Splitter for Broadband Operation using a Genetic Algorithm
摘要： We present a design method for a polarization beam splitter for broadband operation based on a genetic algorithm (GA). The devices are segmented into short sections, where the geometric parameters for each device are determined using a GA.
关键词： genetic algorithm,silicon photonics,directional coupler,broadband,optimization,beam splitter
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - An Optimized Ultrathin and Broadband Metamaterial Absorber Using Slotted Square Loop with Multi Layers
摘要： An optimized ultrathin and broadband absorber is proposed in this paper. It is composed of a periodic array of slotted square loop-dielectric multilayered structure. The bottom layer consists of one dielectric with edge-overlapped slotted square metal loop on it. The simulated results indicate that the absorption at normal incidence is above 90% in almost the whole frequency range of 6.25-18GHz. Moreover, the designed absorber is ultrathin with a thickness of only 0.13-0.38 free-space wavelength at the lowest and highest frequencies, respectively.
关键词： broadband absorber,slotted square loop,Metamaterial,anti-reflection,multi-layer
更新于2025-09-23 15:22:29
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Ultra-broadband, sensitive and fast photodetection with needle-like EuBiSe3 single crystal
摘要： Ultra-broadband photodetection has been a hot topic with the rapid development of materials science and the application requirements for communication, imaging and sensing. Photodetectors based on bandgap-independent bolometry are promising candidates for detection of light from the ultraviolet to the terahertz range. Here we report a photothermoelectric detector made of an alloy of EuBiSe3 single crystal. The device shows room-temperature self-powered photoresponse from ultraviolet (375 nm) to terahertz (163 μm) with nearly uniform sensitivity against wavelength and fast response speed. Thanks to the large thermoelectric power (Seebeck coefficient) of EuBiSe3, the photovoltage responsivity derived from the incident (not absorbed) power reaches as high as 1.69 V/W at 405 nm without any bias voltage, and exceeds 0.59 V/W even at terahertz frequencies, with noise-equivalent power below 1 nW/√Hz, which is 1–2 orders of magnitude lower than reported photothermoelectric detectors. The response time is around 200 ms, nearly two orders of magnitude faster than silicon-based heterojunction ultra-broadband photodetectors and on the same order as the millimetric-scale graphene- and carbon nanotube-based bolometric photodetectors. In addition, the as-grown EuBiSe3 crystal possesses a unique needle-like shape, intrinsically facilitating integration of the detector. Our work demonstrates that improved thermoelectric materials hold great promise for room-temperature high-performance broadband photodetection.
关键词： EuBiSe3,photothermoelectric,ultra-broadband,sensitive,photodetector,self-powered
更新于2025-09-23 15:22:29
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Robust high-fidelity coherent control of two-state systems by detuning pulses
摘要： Coherent control of two-state systems is traditionally achieved by resonant pulses of specific Rabi frequency and duration, by adiabatic techniques using level crossings or delayed pulses, or by sequences of pulses with precise relative phases (composite pulses). Here we develop a method for high-fidelity coherent control which uses a sequence of detuning pulses. By using the detuning pulse areas as control parameters, and driving on an analogy with composite pulses, we report a great variety of detuning pulse sequences for broadband and narrow-band transition probability profiles.
关键词： composite pulses,narrow-band,coherent control,broadband,detuning pulses,two-state systems
更新于2025-09-23 15:22:29
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Engineering hierarchical porous oxygen-deficient TiO2 fibers decorated with BiOCl nanosheets for efficient photocatalysis
摘要： The hierarchical porous oxygen-deficient TiO2 (TiO2-δ) fibers decorated with BiOCl nanosheets, for the first time, were synthesized through a sol-gel method combined with centrifugal spinning, and subsequent heat treatment under steam. Therein, the byproduct water-soluble NaCl crystal was recycled and used as the self-manufactured and self-sacrificial template. The dissolving out of NaCl for the in situ preparation of BiOCl on the surface of TiO2-δ generates rich mesoporous fiber structure. The flower-like BiOCl nanosheets provide large surface area for the adsorption of reactants, and more light scattering/reflection channels for enhancing light absorption. A series of characterizations confirmed that the introduction of oxygen vacancies in TiO2 broadens the light response to visible range, and the promotion of charge separation due to the formation of p-n junction between BiOCl and TiO2-δ. As a result, the BiOCl/TiO2-δ fiber exhibits enhanced broadband photocatalytic performance in the degradation of reactive brilliant red and colorless phenol. The apparent reaction rate constant achieved by the optimized BiOCl/TiO2-δ composite (0.0636 min-1) far surpasses that of TiO2-δ fibers (0.0026 min-1) by a factor of 24 under visible light irradiation. The reactive species involved in photocatalysis were detected by scavenger experiments and electron spin resonance spectra. The possible charge transfer processes and mechanism were explored and discussed in detail. This work provides novel insight into the design and synthesis of broadband and effective heterostructure photocatalysts for practical wastewater treatment.
关键词： BiOCl,oxygen-deficient TiO2,p-n junction,broadband photocatalysis
更新于2025-09-23 15:21:21
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Ultrathin Flexible Carbon Fiber Reinforced Hierarchical Metastructure for Broadband Microwave Absorption with Nano Lossy Composite and Multi-scale Optimization
摘要： The implementation of thin structure for broadband microwave absorption is challenging due to requirement of impedance match across several frequency bands and poor mechanical properties. Herein, we demonstrate a carbon fiber (CF) reinforced flexible thin hierarchical metastructure (HM) composed of lossy materials including carbonyl iron (CI), multiwall carbon nanotube (MWCNT) and silicone rubber (SR) with thickness of 5mm and optimal concentration selected from twelve formulae. Optimization for the periodical unit size is applied and impacts of structural sizes on absorption performance is also investigated. An effective process combining the vacuum bag method and the hand lay-up technique is used to fabricate the HM. Experimental reflectivity of the absorber achieves broadband absorption below -10dB in 2-4GHz and 8-40GHz. Full band in 2-40GHz is covered below -8dB. Yielding stress of the HM is increased to 24MPa with attachment of CF while the fracture strain of the composite reaches 550%. The soft HM is suitable to adhere to curved surface of objects needed to be protected from microwave radiation detection and electromagnetic interference. Enhanced mechanical properties make it possible for further practical applications under harsh service environment such as ocean and machines with constant vibration.
关键词： broadband microwave absorption,hierarchical metastructure,dielectric-magnetic lossy material,flexible,mechanical properties
更新于2025-09-23 15:21:21