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- 摘要
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- 实验方案
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[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) - Linear-to-Circular Polarization Conversion For Beam-Scanning Antenna Based On Self-Complementary Metasurface
摘要： Modular multilevel converters (MMC) are presently the converter topology of choice for voltage-source converter high-voltage direct-current (VSC-HVDC) transmission schemes due to their very high efficiency. These converters are complex, yet fast and detailed electromagnetic transients simulation models are necessary for the research and development of these transmission schemes. Excellent work has been done in this area, though little objective comparison of the models proposed has yet been undertaken. This paper compares for the first time, the three leading techniques for producing detailed MMC VSC-HVDC models in terms of their accuracy and simulation speed for several typical simulation cases. In addition, an improved model is proposed which further improves the computational efficiency of one method. This paper concludes by presenting evidence-based recommendations for which detailed models are most suitable for which particular studies.
关键词： HVDC transmission,electromagnetic-transient (EMT) simulation,voltage-source converter (VSC),modular multilevel converter (MMC),Accelerated model
更新于2025-09-23 15:19:57
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Comparison of effects of ZnO and TiO2 compact layer on performance of perovskite solar cells
摘要： In this work, organic?inorganic perovskite solar cells using compact layers of TiO2 and ZnO have been constructed. The ZnO compact layer was synthesized through the chemical hydrolysis process. The TiO2 compact layer was formed by spin-coating C16H28O6Ti in n-butanol. AFM and light absorption studies showed that the surface roughness and optical property of TiO2 and ZnO are nearly identical. However, according to the energy level diagram, the conduction band edge of ZnO is lower than that of TiO2, which is beneficial for electron transfer from the light absorption material to the FTO substrate and thus reducing electron-hole recombination. As a result, employing ZnO in the cell improved both the photocurrent and photovoltaic performance in comparison to TiO2. The best conversion efficiency obtained from the device using ZnO as the compact layer is 17.1%, which is attributed to facilitated photo-generated electron transport in the perovskite solar cell.
关键词： Electronic Transmission,Energy Level.,Compact Layer
更新于2025-09-23 15:19:57
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Mechanisms of Fano-resonant biosensing: Mechanical loading of plasmonic oscillators
摘要： Distinctively narrow and asymmetric line shape Fano resonances arise due to resonant interactions of sub-radiant and super-radiant modes in plasmonic nanostructures and metamaterials. A number of recent experimental studies have shown unique opportunities provided by highly dispersive Fano resonances in biosensing applications. However, there is limited understanding of Fano resonant optical response to biomolecular accumulation. Here, we introduce a phenomenological model that can precisely describe the intricate nature of the Fano resonances in plasmonic nanohole arrays and provide unambiguous physical insights into biosensing experiments. Using rigorous electromagnetic simulations and experimental measurements as benchmarking tools, we show that the non-trivial contribution of molecular accumulation to Fano resonant plasmonic response can be incorporated as a mechanical loading effect in a coupled-oscillator model. Quite remarkably, our phenomenological approach captures the complex spectral response of the Fano resonance profile and asymmetric linewidth broadening upon molecular accumulation. Furthermore, in strong agreement with our experimental measurements, we show that our parameterized model has predictive power in fine tuning the Fano resonant extraordinary light transmission lineshape using structural design parameters without resorting to electromagnetic simulations. Our phenomenological model provides a general analytical method that can be adapted to understand biomolecular detection measurements in different plasmonic and metamaterial systems.
关键词： Biosensing,Extraordinary light transmission,Plasmonics,Plasmonic nanoholes,Fano resonances,Label-free detection
更新于2025-09-23 15:19:57
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A study on the heat distribution and oxidative modification of aged dammar films upon Er:YAG laser irradiation
摘要： This work shows the impact of one Er:YAG laser pulse to both the surface and bulk of aged dammar varnishes. Tests were performed in fluences ranging from 0.56 to 2.4J/cm2 and pulse durations of 100 and 300μs. Temperature changes upon irradiation were examined by (a) live recordings with an infrared thermal camera, and (b) determining the optical properties of the varnish, which allowed for estimates of the linear absorption coefficient and the temperature rise associated with the laser irradiation. Transmission and Fourier Transform Infrared (FTIR) spectroscopy studies captured increased energy transmissions through varnish films, as well as registering a reduction of hydroxides and carbon–hydrogen bonding as a function of fluence, respectively. FTIR and Differential Scanning Calorimetry (DSC) experimentally determined the absorption coefficient and the specific heat capacity of dammar films, and an overview of laser spots was carried out with Scanning Electron Microscopy (SEM). Evidence on the varnish response to Er:YAG laser irradiation is provided.
关键词： Er:YAG lasers,transmission,thermal effects,dammar varnish,analysis,modelling
更新于2025-09-23 15:19:57
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Scattering singularities of optical waveguides under complex modulation
摘要： We employ complex index modulation to manipulate light scattering in a waveguide and achieve different kinds of singularities in the system. The singularities refer to poles or zeros in the scattering and transfer matrices. By using spatially complex index modulation, we realize unidirectional zero-re?ection singularities, which can be manipulated by adjusting the modulation phase difference between the real and imaginary parts. Laser-coherent perfect absorber singularities with both diverging re?ectance and transmittance are also achieved by cascading two waveguides with different modulation phases. Meanwhile, bidirectional zero-re?ection singularities with re?ectionless light transporting on both sides of the waveguides are also demonstrated. In addition, we utilize temporally complex modulation to obtain transfer matrix singularities and achieve nonreciprocal light transmission. The study may ?nd great applications in light ampli?cation, attenuation, and absorption, as well as constructing nonreciprocal optical devices.
关键词： scattering singularities,complex modulation,optical waveguides,nonreciprocal light transmission
更新于2025-09-23 15:19:57
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Compact and low-power all-optical surface plasmon switches with isolated pump and data waveguides and a rectangular cavity containing nano-silver strips
摘要： In this paper, a plasmonic all-optical switch based on a novel topology is presented. The structure is composed of a rectangular cavity coupled with two cross waveguides. Several silver strips with a tapered pattern are inserted in the rectangular cavity to create a sharp edge in the transmission spectrum of the data signal. The cavity and waveguides are filled with a non-linear insulator with high Kerr-type nonlinearity. The vertical and horizontal waveguides are used for passing the data and pump signals, respectively. When in addition to the data signal, the pump signal is also applied, the refractive index of the Kerr material changes, which triggers the switching mechanism. Allocating two different paths for the data and pump signals results in a desirable isolation between these signals. The proposed switch is numerically simulated using finite difference time domain (FDTD) method. In order to verify the FDTD simulation results, the basic switch structure is also analyzed using the transmission line method. Compact size (considering two different input ports), low pumping intensity, simplicity, symmetrical structure, suitable isolation and high contrast ratios are the marked characteristics of the proposed all-optical switch. As a result, such a structure has the potential to be used in complex integrated optical circuits.
关键词： Surface plasmon polaritons,Transmission line method,Metal-insulator-metal waveguide,All-optical switch,Kerr effect,Metal strips
更新于2025-09-23 15:19:57
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Single-Layer Dual-Band Polarization-Selective Metafilm with Independently Controlled and Closely Spaced Shielding Bands
摘要： Spatially distributed transmissions in coordinated multipoint (CoMP) systems can lead to mean channel power imbalance (CPI) at the receiver. Similar imbalance also occurs in distributed antenna and co-located multi-antenna systems due to inaccurate antenna calibration. This paper studies performance impact of power imbalance on some practical CoMP methods with limited feedback. We derive approximate analytical expressions of asymptotic capacity, optimal amplitude weights, as well as signal-to-noise ratio gain for a few methods under analysis. Numerical results validate the analysis and show impacts of erroneous feedback under CPI. Results demonstrate that CPI has significant negative impact on the CoMP performance. Furthermore, our results reveal that amplitude information at transmitter is crucial and detrimental effect of CPI can be effectively compensated by using long-term amplitude information at transmitter. Moreover, additional short-term amplitude feedback shows insignificant gain when a large number of diversity antennas in base stations or CoMP suffer from feedback errors. In fact, a sparsely quantized phase and long-term power information feedback can lead to performance very close to the use of full channel state information at the transmitter.
关键词： transmit beamforming,Coordinated multipoint transmission,distributed antenna system,channel power imbalance
更新于2025-09-23 15:19:57
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Visualizing Speech-Generated Oral Fluid Droplets with Laser Light Scattering
摘要： Aerosols and droplets generated during speech have been implicated in the person-to-person transmission of viruses, and there is current interest in understanding the mechanisms responsible for the spread of Covid-19 by these means. The act of speaking generates oral fluid droplets that vary widely in size, and these droplets can harbor infectious virus particles. Whereas large droplets fall quickly to the ground, small droplets can dehydrate and linger as “droplet nuclei” in the air, where they behave like an aerosol and thereby expand the spatial extent of emitted infectious particles. We report the results of a laser light-scattering experiment in which speech-generated droplets and their trajectories were visualized.
关键词： Covid-19,speech,virus transmission,laser light-scattering,droplets,aerosols
更新于2025-09-23 15:19:57
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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - 2 ??m Thulium-doped Fiber Laser Based on Synchronously Pumped Mode-locking
摘要： Mobile fronthaul is an important network segment that bridges wireless baseband units and remote radio units to support cloud radio access network. We review recent progresses on the use of frequency-division multiplexing to achieve highly bandwidth-efficient mobile fronthaul with low latency. We present digital signal processing (DSP) techniques for channel aggregation and deaggregation, frequency-domain windowing, adjacent channel leakage ratio reduction, and synchronous transmission of both the I/Q waveforms of wireless signals and the control words (CWs) used for control and management purposes. In a proof-of-concept experiment, we demonstrate the transmission of 48 20-MHz LTE signals with a common public radio interface (CPRI) equivalent data rate of 59 Gb/s, achieving a low round-trip DSP latency of <2 μs and a low mean error-vector magnitude (EVM) of ～2.5% after fiber transmission. In a follow-up experiment, we further demonstrate the transmission of 32 20-MHz LTE signals together with CPRI-compliant CWs, corresponding to a CPRI-equivalent data rate of 39.32 Gb/s, in single optical wavelength channel that requires an RF bandwidth of only ～1.6 GHz. After transmission over 5-km standard single-mode fiber, the CWs are recovered without error, while the LTE signals are recovered with an EVM of lower than 3%. Applying this technique to future 5G wireless networks with massive multiple-input multiple-output is also discussed. This efficient mobile fronthaul technique may find promising applications in future integrated fiber/wireless access networks to provide ultrabroadband access services.
关键词： fifth-generation (5G),common public radio interface (CPRI),Cloud radio access network (C-RAN),optical fiber transmission,mobile fronthaul,frequency-division multiplexing (FDM)
更新于2025-09-23 15:19:57
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Structural Transformations of a Carbon Nanomaterial under High-Energy Laser Irradiation
摘要： Pulsed-laser irradiation of a globular turbostratic carbon material under diverse conditions was carried. A TEM examination revealed formation of nanostructured particles (nanocapsules) under exposure to 1064 nm pulsed radiation at the power density of 108 W/cm2, whose increase to 1011 W/cm2 led to formation of structures with a higher degree of ordering. Pulsed irradiation of the initial globules at 532 nm wavelength allowed reducing the interplanar spacings of the graphene layers in the resultant nanocapsules from 0.410 to 0.346 nm. The dependence of the maximum heating temperature of the nanoparticles on the power density in the laser spot was analyzed. The in? uence of the heating temperature of the carbon nanomaterial on its structure and morphology was assessed.
关键词： carbon nanomaterials,nanocapsules,power density,transmission electron microscopy,laser irradiation
更新于2025-09-23 15:19:57