- 标题
- 摘要
- 关键词
- 实验方案
- 产品
过滤筛选
- 2018
- 2015
- periodic paperclip-shaped structure
- antenna array
- mutual coupling reduction
- Bessel Function
- Coupling Coefficient
- Fusion temperature and Elongation speed
- Electronic Science and Technology
- Physics
- UIN Suska Riau
- Xi'an University of the Science and Technology
- University of Riau
-
Heavy Atom Effect of Selenium for Metal-Free Phosphorescent Light-Emitting Diodes
摘要： Room-temperature phosphorescence from metal-free purely organic molecules has recently gained much interest. We devised metal-free organic phosphors by incorporating selenium (Se) to promote spin?orbit coupling by its nonmetal heavy atom effect. The Se-based organic phosphors showed bright phosphorescent emission in organic light-emitting diodes (OLEDs) and photo-excited phosphorescence in an amorphous film state. Large orbital angular momentum change (ΔL) during the electron transition process and heavy atom effect of Se render a PL quantum yield of 0.33 ± 0.01 and a high external quantum efficiency (EQE) of 10.7 ± 0.14% in phosphorescent LEDs. This work demonstrates the rational molecular design of metal-free organic phosphorescent emitters with Se as an alternative novel class of materials to the conventional organometallic phosphors for OLEDs.
关键词： organic light-emitting diodes,spin?orbit coupling,selenium,metal-free organic phosphors,phosphorescent LEDs,room-temperature phosphorescence
更新于2025-09-23 15:19:57
-
Tailoring the plasmonic Fano resonance in metallic photonic crystals
摘要： Periodically arranged metallic nanowires on top of a waveguide layer show a strong coupling between the particle plasmon of the wires and the waveguide mode. By introducing a dielectric spacer layer between the metallic structures and the waveguide layer, this coupling can be reduced. Here, the thickness of this spacer layer is varied and the coupling strength is determined for each spacer layer thickness by fitting an effective energy matrix to the energy positions of the resonance peaks. It is found that the coupling strength can be very well described by the electric field amplitude of the waveguide mode at the location of the nanowires. We carried out experiments and found very good agreement with theory and our simple model. Using this method, we achieved experimentally an extremely small mode splitting as small as 25 meV leading to very sharp spectral features. Our pathway and design for tailoring the coupling strength of plasmonic Fano resonances will enable the design of highly sensitive plasmonic sensor devices and open the door for narrow plasmonic spectral features for nonlinear optics and slow light propagation.
关键词： photonic crystals,coupling strength,Fano resonance,plasmonic,waveguide
更新于2025-09-23 15:19:57
-
Charge coupling in multi-stage laser wakefield acceleration
摘要： The multi-stage technique in the laser driven acceleration of electrons has become a critical part for full-optical jitter-free accelerators. Several independent laser drivers and shorter plasma targets allow the stable and reproducible acceleration of electron bunches (or beam) at the GeV energies with narrower energy spreads. Moreover, the charge coupling, necessary for ef?cient acceleration in the consecutive acceler-ation stages, depends collectively on the parameters of the injected electron beam, the booster stage, and the nonlinear transverse dynamics of the electron beam in the laser pulse wake. An unmatched electron beam injected in the booster stage and its nonlinear transverse evolution may result in perturbations and even a reduction of the ?eld strength in the acceleration phase of the wake?eld. Thus, the analysis and characterization of charge coupling in multi-stage laser wake?eld acceleration (LWFA) are important. Here, we investigate acceleration of an externally injected electron beam in the laser wake?eld, emulating two-stage LWFA, using fully relativistic multi-dimensional particle-in-cell simulations. We also study the underlying critical parameters that affect the ef?cient coupling and acceleration of the injected electron beam in the booster stage.
关键词： charge coupling,multi-stage,electron beam,plasma wave,laser wakefield acceleration
更新于2025-09-23 15:19:57
-
Simulation of structural design with high coupling efficiency in external cavity semiconductor laser
摘要： For external cavity semiconductor lasers (ECSLs), high coupling efficiency is critical to reducing the linewidth. In this paper, the coupling efficiency between the laser diode and the waveguide grating has been improved, with proposals for its improvement presented, including adding spot-size conversion (SSC) and using a silicon-on-insulator (SOI) waveguide. The results indicate an increase of coupling efficiency from 41.5% to 93.1%, which exhibits an improvement of approximately 51.6% over conventional schemes. The relationship between coupling efficiency and SOI waveguide structures is mainly concerned in this article. These findings provide a new way for the future research of the narrow linewidth of ECSL.
关键词： SOI waveguide,coupling efficiency,spot-size conversion
更新于2025-09-23 15:19:57
-
[IEEE 2019 21st International Middle East Power Systems Conference (MEPCON) - Cairo, Egypt (2019.12.17-2019.12.19)] 2019 21st International Middle East Power Systems Conference (MEPCON) - Experimental Realization for P&O Maximum Power Point Tracking Applied for Single-Stage Three-Phase Grid-Connected Photovoltaic System
摘要： This paper presents a point of care testing device for neurovascular coupling (NVC) from simultaneous recording of electroencephalogram (EEG) and near infrared spectroscopy (NIRS) during anodal transcranial direct current stimulation (tDCS). Here, anodal tDCS modulated cortical neural activity leading to hemodynamic response can be used to identify the impaired cerebral microvessels functionality. The impairments in the cerebral microvessels functionality may lead to impairments in the cerebrovascular reactivity (CVR), where severely reduced CVR predicts the chances of transient ischemic attack and ipsilateral stroke. The neural and hemodynamic responses to anodal tDCS were studied through joint imaging with EEG and NIRS, where NIRS provided optical measurement of changes in tissue oxy-(HbO2) and deoxy-(Hb) hemoglobin concentration and EEG captured alterations in the underlying neuronal current generators. Then, a cross-correlation method for the assessment of NVC underlying the site of anodal tDCS is presented. The feasibility studies on healthy subjects and stroke survivors showed detectable changes in the EEG and the NIRS responses to a 0.526 A/m2 of anodal tDCS. The NIRS system was bench tested on 15 healthy subjects that showed a statistically signi?cant (p < 0.01) difference in the signal-to-noise ratio (SNR) between the ON- and OFF-states of anodal tDCS where the mean SNR of the NIRS device was found to be 42.33 ± 1.33 dB in the ON-state and 40.67±1.23 dB in the OFF-state. Moreover, the clinical study conducted on 14 stroke survivors revealed that the lesioned hemisphere with impaired circulation showed signi?cantly (p < 0.01) less change in HbO2 than the nonlesioned side in response to anodal tDCS. The EEG study on healthy subjects showed a statistically signi?cant (p < 0.05) decrease around individual alpha frequency in the alpha band (8–13 Hz) following anodal tDCS. Moreover, the joint EEG-NIRS imaging on 4 stroke survivors showed an immediate increase in the theta band (4–8 Hz) EEG activity after the start of anodal tDCS at the nonlesioned hemisphere. Furthermore, cross-correlation function revealed a signi?cant (95% con?dence interval) negative cross correlation only at the nonlesioned hemisphere during anodal tDCS, where the log-transformed mean-power of EEG within 0.5–11.25 Hz lagged HbO2 response in one of the stroke survivors with white matter lesions. Therefore, it was concluded that the anodal tDCS can perturb the local neural and the vascular activity (via NVC) which can be used for assessing regional NVC functionality where con?rmatory clinical studies are required.
关键词： Hilbert-Huang transform,Electroencephalogram,neurovascular coupling,small vessel diseases,stroke,near infrared spectroscopy,transcranial direct current stimulation
更新于2025-09-23 15:19:57
-
[IEEE 2018 11th UK-Europe-China Workshop on Millimeter Waves and Terahertz Technologies (UCMMT) - HangZhou, China (2018.9.5-2018.9.7)] 2018 11th UK-Europe-China Workshop on Millimeter Waves and Terahertz Technologies (UCMMT) - Input coupling systems for terahertz gyro-TWAs
摘要： Input coupling systems for THz gyrotron traveling wave amplifiers (gyro-TWAs) are presented in this paper. These form one of the most critical parts of the gyro-TWA as it feeds the low power seed signal into the interaction circuit and incorrect design can lead to cessation of the amplification. The T-junction, multihole and multiarm coupler types were simulated in CST Microwave Studio and their optimized reflection and transmission characteristics, operating at a central frequency of 0.37 THz are presented. A scaled multiarm coupler, designed to then operate at 94 GHz, was manufactured and its microwave properties measured on a vector network analyser.
关键词： CST Microwave Studio,multihole coupler,THz gyro-TWAs,T-junction,multiarm coupler,input coupling systems
更新于2025-09-23 15:19:57
-
Plasmonic heating using an easily recyclable Pda??functionalized Fe <sub/>3</sub> O <sub/>4</sub> /Au corea??shell nanoparticle catalyst for the Suzuki and Sonogashira reaction
摘要： Palladium functionalized gold nanoparticles were used in the past as a catalyst system in light induced cross-coupling reactions, but with a main limitation of the recuperation. To overcome this problem, a palladium functionalized Fe3O4/Au core-shell nanoparticle was successfully synthesized with a peak wavelength of 680 nm from the plasmon resonance of the gold shell. By the presence of the magnetite core, the nanoparticle catalyst can easily be removed using magnetic precipitation. This is accompanied with the advantage of having less valuable gold present in the system. The gold shell makes it possible to induce local heating using plasmon resonance. By this combination, it is possible to recuperate the catalyst system using magnetic precipitation and increase the control and safety of the reaction due to the presence of the light-induced plasmonic heating. It was possible to perform light-induced Suzuki cross-coupling reactions using this catalyst system, but with a dependency of the substrate. It was found that an anionic substrate is repulsed from the negatively charged core-shell nanoparticle. The catalyst was examined on its recuperation abilities and could be reused up to 5 cycles. At the catalytic site a temperature was reached between 40 °C and 45 °C. Despite the promising results of the Suzuki reaction, it was not possible to perform light-induced Sonogashira reactions due to the insufficient heat generation at the catalytic site. Nevertheless, these results are promising in the development of an easily recyclable catalyst together with an alternative heating source, resulting in an increase of control and safety.
关键词： cross-coupling reaction,magnetically separable,plasmonic heating,immobilized catalyst
更新于2025-09-23 15:19:57
-
Plasmonic Fano Resonance in Homotactic Aluminum Nanorod Trimer: the Key Role of Coupling Gap
摘要： Recently, the Fano effect of aluminum nanostructures has attracted a lot of attentions in several detector and sensor applications, but the role of coupling gap in it remains unintuitive. In this paper, a homotactic aluminum rod trimer (HART) is designed to form the plasmonic Fano resonances and visualize the important role of coupling gap size. The plasmon hybridization model and far field images were used to qualitatively describe the formation mechanism of Fano resonance. The simulation results intuitively show that the Fano dip of HART with a smaller coupling gap size has a higher red-shift speed when increasing the refractive index of surrounding environment or the length of HART with a fixed axial ratio (LS/LL = 0.6). Our study provides the insights to the key role of coupling gap in the performance of Fano structures.
关键词： Fano resonance,Aluminum nanorods,Far field,Plasmon,Coupling gap
更新于2025-09-23 15:19:57
-
A criterion of the vertical spacing between fluorescent molecules in a waveguide structure
摘要： We demonstrate a method to discriminate the vertical spacing of ?uorescent molecules in a guided mode structure. A function that depends only on depth and wavelength is constructed to detect the axial position of a pair of ?uorescent molecules, which is especially suitable for the measurement of microstructure gaps and is not a?ected by the di?raction limit. Since directional ?uorescence radiation information can be collected from the back focal plane in a leakage radiation microscope, we can utilize the appropriate emission angles and corresponding waveguide modes. The relative position of the ?uorescent molecules is calculated by analyzing the intensity ratio between modes emission, so as to determine the vertical distance between the molecules.
关键词： Leakage radiation microscopy,Guided wave coupling emission,Molecular spacing,Surface plasmons
更新于2025-09-23 15:19:57
-
Experimental Realization of Two-Dimensional Buckled Lieb lattice
摘要： Two-dimensional (2D) materials with a Lieb lattice host exotic electronic band structures. Such a system does not exist in nature, and it is also difficult to obtain in the laboratory due to its structural instability. Here, we experimentally realized a 2D system composed of a tin overlayer on an aluminum substrate by molecular beam epitaxy. The specific arrangement of Sn atoms on the Al(100) surface, which benefits from favorable interface interactions, forms a stabilized buckled Lieb lattice. Theoretical calculations indicate a partially broken nodal line loop and a topologically nontrivial insulating state with a spin-orbital coupling effect in the band structure of this Lieb lattice. The electronic structure of this system is experimentally characterized by angle-resolved photoemission spectroscopy, in which the hybridized states between topmost Al atoms and Sn atoms are revealed. Our work provides an appealing method for constructing 2D quantum materials based on the Lieb lattice.
关键词： Lieb lattice,nodal line,geometry,topological insulating state,spin-orbital coupling,2D materials
更新于2025-09-23 15:19:57