scholarly journals Full 360∘ Terahertz Dynamic Phase Modulation Based on Doubly Resonant Graphene-Metal Hybrid Metasurfaces

2021 ◽  
Author(s):  
Binxu Wang ◽  
Xiaoqing Luo ◽  
Yalin Lu ◽  
Guangyuan Li
Keyword(s):  
Fermi Energy ◽  
Phase Modulation ◽  
Beam Steering ◽  
Polarization Conversion ◽  
Terahertz Waves ◽  
Dynamic Phase ◽  
Phase Profile ◽  
Profile Design ◽  
Simulation Results ◽  
High Reflectance

Dynamic phase modulation is vital for tunable focusing, beaming, polarization conversion and holography. However, it remains challenging to achieve full 360∘ dynamic phase modulation while maintaining high reflectance or transmittance based on metamaterials or metasurfaces in the terahertz regime. Here we propose a doubly resonant graphene-metal hybrid metasurface to address this challenge. Simulation results show that by varying the graphene Fermi energy, the proposed metasurface with two shifting resonances is capable to provide dynamic phase modulation covering a range of 361∘ while maintaining relatively high reflectance above 20% at 1.05 THz. Based on the phase profile design, dynamically tunable beam steering and focusing are numerically demonstrated. We expect this work will advance the engineering of graphene metasurfaces for the dynamic manipulation of terahertz waves.

scholarly journals Full 360° Terahertz Dynamic Phase Modulation Based on Doubly Resonant Graphene–Metal Hybrid Metasurfaces

Nanomaterials ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 3157
Author(s):  
Binxu Wang ◽  
Xiaoqing Luo ◽  
Yalin Lu ◽  
Guangyuan Li
Keyword(s):  
Fermi Energy ◽  
Phase Modulation ◽  
Beam Steering ◽  
Terahertz Waves ◽  
Dynamic Phase ◽  
Phase Profile ◽  
Profile Design ◽  
Simulation Results ◽  
High Reflectance ◽  
Dynamic Manipulation

Dynamic phase modulation is vital for tuneable focusing, beaming, polarisation conversion and holography. However, it remains challenging to achieve full 360° dynamic phase modulation while maintaining high reflectance or transmittance based on metamaterials or metasurfaces in the terahertz regime. Here, we propose a doubly resonant graphene–metal hybrid metasurface to address this challenge. Simulation results show that by varying the graphene Fermi energy, the proposed metasurface with two shifting resonances is capable of providing dynamic phase modulation covering a range of 361° while maintaining relatively high reflectance above 20% at 1.05 THz. Based on the phase profile design, dynamically tuneable beam steering and focusing were numerically demonstrated. We expect that this work will advance the engineering of graphene metasurfaces for the dynamic manipulation of terahertz waves.

scholarly journals Scattering Analysis and Efficiency Optimization of Dielectric Pancharatnam–Berry-Phase Metasurfaces

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 586
Author(s):  
Chen-Yi Yu ◽  
Qiu-Chun Zeng ◽  
Chih-Jen Yu ◽  
Chien-Yuan Han ◽  
Chih-Ming Wang
Keyword(s):  
Phase Modulation ◽  
Rotation Angle ◽  
Berry Phase ◽  
Fine Tuning ◽  
Design Rule ◽  
Polarization Conversion ◽  
Swarm Optimization ◽  
Efficiency Optimization ◽  
Phase Type ◽  
Gradient Phase

In this study, the phase modulation ability of a dielectric Pancharatnam–Berry (PB) phase metasurface, consisting of nanofins, is theoretically analyzed. It is generally considered that the optical thickness of the unit cell of a PB-phase metasurface is λ/2, i.e., a half-waveplate for polarization conversion. It is found that the λ/2 is not essential for achieving a full 2π modulation. Nevertheless, a λ/2 thickness is still needed for a high polarization conversion efficiency. Moreover, a gradient phase metasurface is designed. With the help of the particle swarm optimization (PSO) method, the wavefront errors of the gradient phase metasurface are reduced by fine-tuning the rotation angle of the nanofins. The diffraction efficiency of the gradient phase metasurface is thus improved from 73.4% to 87.3%. This design rule can be utilized to optimize the efficiency of phase-type meta-devices, such as meta-deflectors and metalenses.

A Linear Acoustic Phased Array for Nonreciprocal Transmission and Reception

2020 ◽  
Author(s):  
R. Adlakha ◽  
M. Moghaddaszadeh ◽  
M. A. Attarzadeh ◽  
A. Aref ◽  
M. Nouh
Keyword(s):  
Phase Modulation ◽  
Frequency Conversion ◽  
Phased Array ◽  
Space Time ◽  
Mathematical Framework ◽  
Sound Waves ◽  
Asymmetric Transmission ◽  
Time Modulation ◽  
Dynamic Phase ◽  
Phase Angles

Abstract Acoustic phased arrays are capable of steering and focusing a beam of sound via selective coordination of the spatial distribution of phase angles between multiple sound emitters. Here, we propose a controllable acoustic phased array with space-time modulation that breaks time-reversal symmetry, and enables phononic transition in both momentum and energy spaces. By leveraging the dynamic phase modulation, the proposed linear phased array is no longer bound by the reciprocity principle, and supports asymmetric transmission and reception patterns that can be tuned independently. Through theoretical and numerical investigations, we develop and verify a mathematical framework to characterize the nonreciprocal phenomena, and analyze the frequency conversion between the wave fields. The space-time acoustic phased array facilitates unprecedented control over sound waves in a variety of applications including underwater telecommunication.

Transmissive 2-bit anisotropic coding metasurface

2022 ◽  
Author(s):  
Pengtao Lai ◽  
Zenglin Li ◽  
Wei Wang ◽  
Jia Qu ◽  
Liang Wei Wu ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Electromagnetic Wave ◽  
Circular Polarization ◽  
Orbital Angular Momentum ◽  
Electromagnetic Waves ◽  
Beam Splitter ◽  
Far Field ◽  
Polarization Conversion ◽  
Field Patterns ◽  
Phase Profile

Abstract Coding metasurfaces have attracted tremendous interests due to unique capabilities of manipulating electromagnetic wave. However, archiving transmissive coding metasurface is still challenging. Here we propose a transmissive anisotropic coding metasurface that enables the independent control of two orthogonal polarizations. The polarization beam splitter and the OAM generator have been studied as typical applications of anisotropic 2-bit coding metasurface. The simulated far field patterns illustrate that the x and y polarized electromagnetic waves are deflected into two different directions, respectively. The anisotropic coding metasurface has been experimentally verified to realize an orbital angular momentum (OAM) beam with l = 2 of right-handed polarized wave, resulting from both contributions from linear-to-circular polarization conversion and the phase profile modulation. This work is beneficial to enrich the polarization manipulation field and develop transmissive coding metasurfaces.

scholarly journals Transparent Metasurface for Generating Microwave Vortex Beams with Cross-Polarization Conversion

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2448 ◽  
Author(s):  
Hongyu Shi ◽  
Luyi Wang ◽  
Mengran Zhao ◽  
Juan Chen ◽  
Anxue Zhang ◽  
...  
Keyword(s):  
Transmission Loss ◽  
Phase Distribution ◽  
Polarization Conversion ◽  
Vortex Beam ◽  
Cross Polarization ◽  
Measurement Results ◽  
Vortex Beams ◽  
Simulation Results ◽  
Polarization Level ◽  
Transmission Phase

In this paper, metasurfaces with both cross-polarization conversion and vortex beam-generating are proposed. The proposed finite metasurface designs are able to change the polarization of incident electromagnetic (EM) waves to its cross-polarization. In addition, they also can modulate the incidences into beams carrying orbital angular momentum (OAM) with different orders ( l = + 1 , l = + 2 , l = − 1 and l = − 2 ) by applying corresponding transmission phase distribution schemes on the metasurface aperture. The generated vortex beams are at 5.14 GHz. The transmission loss is lower than 0.5 dB while the co-polarization level is −10 dB compared to the cross-polarization level. The measurement results confirmed the simulation results and verified the properties of the proposed designs.

scholarly journals Terahertz Beam Steering Concept Based on a MEMS-Reconfigurable Reflection Grating

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 2874
Author(s):  
Xuan Liu ◽  
Lisa Samfaß ◽  
Kevin Kolpatzeck ◽  
Lars Häring ◽  
Jan C. Balzer ◽  
...  
Keyword(s):  
Diffraction Grating ◽  
High Speed ◽  
Beam Steering ◽  
Vertical Displacement ◽  
Grating Period ◽  
Terahertz Waves ◽  
Large Area ◽  
Electrostatic Actuators ◽  
Reflection Gratings ◽  
Reflection Grating

With an increasing number of applications of terahertz systems in industrial fields and communications, terahertz beamforming and beam steering techniques are required for high-speed, large-area scanning. As a promising means for beam steering, micro-electro-mechanical system (MEMS)-based reflection gratings have been successfully implemented for terahertz beam control. So far, the diffraction grating efficiency is relatively low due to the limited vertical displacement range of the reflectors. In this paper, we propose a design for a reconfigurable MEMS-based reflection grating consisting of multiple subwavelength reflectors which are driven by 5-bit, high-throw electrostatic actuators. We vary the number of the reflectors per grating period and configure the throw of individual reflectors so that the reflection grating is shaped as a blazed grating to steer the terahertz beam with maximum diffraction grating efficiency. Furthermore, we provide a mathematical model for calculating the radiation pattern of the terahertz wave reflected by general reflection gratings consisting of subwavelength reflectors. The calculated and simulated radiation patterns of the designed grating show that we can steer the angle of the terahertz waves in a range of up to ± 56.4 ∘ with a maximum sidelobe level of −10 dB at frequencies from 0.3 THz to 1 THz.

An acoustic metasurface with simultaneous phase modulation and energy attenuation

2018 ◽  
Vol 32 (23) ◽  
pp. 1850276 ◽  
Author(s):  
Baozhu Cheng ◽  
Hong Hou ◽  
Nansha Gao
Keyword(s):  
Phase Modulation ◽  
Low Frequency ◽  
Layered Media ◽  
Media Theory ◽  
Wave Direction ◽  
Medium Theory ◽  
Underwater Acoustic ◽  
Potential Applications ◽  
Simulation Results ◽  
Effective Phase

We introduced a rigid structure into the acoustic metasurface design, the proposed labyrinth structure is based on the equivalent medium theory and different media are replaced by curly labyrinth. Layered media theory and equivalent medium theory are combined to design the arbitrary acoustic metasurface structure. An acoustic metasurface studied in this paper realized simultaneous phase modulation and energy attenuation in the air, the effective phase modulation range covered from 30[Formula: see text] to 90[Formula: see text] and the energy attenuation is over 40%. According to layered media theory which could modulate the acoustic wave direction, the metasurface with same function can also be applied to underwater case. Corresponding simulation results are calculated by FEA. Finally, by introducing the curly labyrinth theory, the underwater acoustic metasurface with simultaneous phase modulation and energy attenuation is designed and verified. This paper has potential applications in rigid underwater acoustic metasurface designs with low frequency, adjustable direction and sound energy attenuation.

Rate-Compatible Punctured Ring Convolutional Coded Continuous Phase Modulation

2012 ◽  
Vol 195-196 ◽  
pp. 217-220
Author(s):  
Lei Zhang ◽  
Man Ping Tong ◽  
Hong Bo Wang
Keyword(s):  
Bit Error Rate ◽  
Error Rate ◽  
Phase Modulation ◽  
Euclidean Distance ◽  
Convolutional Codes ◽  
Continuous Phase ◽  
Transmission Efficiency ◽  
Continuous Phase Modulation ◽  
Simulation Results ◽  
Squared Euclidean Distance

In this paper, continuous phase modulation (CPM) with rate-compatible punctured ring convolutional codes is investigated. Some typical schemes with maximum normalized minimum squared euclidean distance (NMSED) are searched and given. The performance of bit error rate for rate-compatible punctured ring convolutional coded CPM on AWGN channel is simulated, and simulation results show that this system can provide good performance of bit error rate and variable-rate capabilities. Furthermore, simulation results also prove that the transmission efficiency increases when code rate is decreasing.

scholarly journals Электронные и теплофизические свойства газовых гидратов: результаты моделирования из первых принципов

2021 ◽  
Vol 63 (2) ◽  
pp. 308
Author(s):  
М.Б. Юнусов ◽  
Р.М. Хуснутдинов ◽  
А.В. Мокшин
Keyword(s):  
Fermi Energy ◽  
Methane Hydrate ◽  
Energy Spectra ◽  
Ab Initio Molecular Dynamics ◽  
Fermi Energy Level ◽  
Density Of Electronic States ◽  
Level Width ◽  
Temperature Dependences ◽  
Simulation Results ◽  
Good Agreement

The results of an ab-initio molecular dynamics study of the electronic and thermophysical properties of methane hydrate with a cubic sI structure are presented. Good agreement of the simulation results for heat capacity at constant volume and density with experimental data is found. Based on the analysis of the density of electronic states, the temperature dependences of the electronic properties of methane hydrate, including the Fermi energy level, width and boundaries of the band gap are determined. For the empty framework of the hydrate (water clathrate framework), the electron energy spectra E(k) were calculated along the directions M-X, X-G, G-M, and G-R. It was found that the presence of CH4 molecules in an aqueous clathrate leads to an increase in the Fermi energy of the hydrate from 2.4 to 3.0 eV.

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