Article
Nanoscience & Nanotechnology
Xiaojian Fu, Lei Shi, Jun Yang, Yuan Fu, Chenxi Liu, Jun Wei Wu, Fei Yang, Lei Bao, Tie Jun Cui
Summary: This study develops a terahertz beam steering device using a liquid-crystal-integrated programmable metasurface. Numerical simulations and experiments demonstrate its phase control and beam steering capabilities.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Materials Science, Multidisciplinary
Xufeng Wang, Xunjun He, Jiuxing Jiang, Yongtao Yao, Guangjun Lu
Summary: In this paper, a reflective hybrid graphene-metal coding metasurface is proposed for programmable manipulation of terahertz beams. The meta-atoms are composed of different C-shaped metallic split-ring resonators integrated with graphene, enabling different coding states through rotation and doping of graphene. The coding metasurfaces can achieve various functionalities including beam deflection, diffusive scattering, and vortex beam by changing the coding patterns. Dynamic reconfiguration is also possible by tuning the Fermi energy of graphene. The proposed coding metasurfaces have great potential in applications such as terahertz sensing, display, telecommunication, and imaging.
DIAMOND AND RELATED MATERIALS
(2022)
Article
Engineering, Electrical & Electronic
Jiashuai Xu, Wenwen Liu, Zhengyong Song
Summary: This paper presents a graphene-based coding metasurface for dynamic beam steering of terahertz waves, demonstrating its versatility in dynamically controlling electromagnetic waves. Experimental results verify the dynamic tunability of the proposed metasurface for various functionalities, showcasing its potential in terahertz wave applications.
IEEE PHOTONICS JOURNAL
(2021)
Article
Materials Science, Multidisciplinary
Chen Xi Liu, Fei Yang, Xiao Jian Fu, Jun Wei Wu, Lei Zhang, Jun Yang, Tie Jun Cui
Summary: Digital coding metasurfaces based on liquid crystals enable programmable terahertz beam manipulations, achieving various functionalities and experimental validation of dual beam steering. This study shows promising potential in imaging, sensing, and wireless communications.
ADVANCED OPTICAL MATERIALS
(2021)
Article
Materials Science, Multidisciplinary
Dongjie Wang, Xunjun He, Bowen Yang, Jiuxing Jiang, Yongtao Yao, Guangjun Lv
Summary: Graphene-functionalized metasurfaces have the potential to actively control linearly polarized waves in the terahertz region, enabling anomalous reflection and amplitude tuning. They can be applied in THz telecommunications, high-resolution THz displays, and advanced THz imaging devices.
DIAMOND AND RELATED MATERIALS
(2022)
Article
Physics, Multidisciplinary
Hazrat But, M. Imtiaz Khan, Rafi Ud Din, Muhammad Zubair, Irfan Mahmood, Pervaiz Ahmad, Guo-Qin Give
Summary: The controlled magneto-optical Faraday rotation (MO-FR) through graphene-based metasurfaces placed on electromagnetically induced transparency (EIT) substrate at terahertz (THz) frequencies is theoretically investigated. By changing the electric field that manipulates the group index of the substrate, MO-FR and transmission of the probe light can be studied. The zero-crossing of MO-FR shifts to higher THz frequencies with increasing the magnetic field, and the polarization plane of MO-FR changes with 180 degrees while increasing the probe field detuning through the EIT substrate.
Article
Optics
Haifeng Xu, Jierong Cheng, Yunyun Ji, Fei Fan, Shengjiang Chang
Summary: Describes a metasurface that uses local phase modulation in subwavelength unit cells for wavefront shaping. Multiple beams are assigned to different diffraction orders located coaxially along the same direction, with their wavefronts tailored by optimizing the diffraction coefficients in two orders and two polarization states of a supercell. By evenly splitting the energy into two orders and adjusting the zeroth-order diffraction phase, a Bessel beam and a vortex beam are simultaneously generated in the near field and far field along a coaxial direction.
Article
Optics
Rui Zhang, Bing You, Shengchuan Wang, Kui Han, Xiaopeng Shen, Weihua Wang
Summary: The proposed broadband and switchable terahertz polarization converters based on graphene metasurfaces exhibit high efficiency in polarization conversion through parameter optimization, making significant progress in THz technology and device applications.
Article
Chemistry, Analytical
Bin Zheng, Xin Rao, Yuyu Shan, Chuandong Yu, Jingke Zhang, Na Li
Summary: This paper proposes a method for reconfigurable antennas using graphene-based coding metasurfaces and designs and simulates various coding sequences for different applications.
Article
Optics
ZengLin Li, Wei Wang, Shaoxuan Deng, Jia Qu, Yuxiang Li, Bo Lv, Wenjia Li, Xi Gao, Zheng Zhu, Chunying Guan, Jinhui Shi
Summary: A VO2-integrated coding metasurface is proposed to achieve thermally controlled scattering-pattern shift through convolution operation. By changing the length of the VO2 cut-wires, the required phase profiles and high amplitudes can be easily obtained.
Article
Optics
Panpeng Ge, Ying Zhang, Lihua Xiao, Binggang Xiao
Summary: We propose a broadband tunable coding metasurfaces structure that utilizes a cruciate metal patch and circular graphene on a multilayer substrate. By changing the Fermi level of the graphene, we achieve significant reflection phase variation for designing multi-bit coding metasurfaces. Combining the advantages of graphene and copper, we realize real-time adjustment of reflected waves in four broadband frequency bands and control the number of far-field reflected waves. Additionally, we create 2-bit and 3-bit coding modes to obtain a single beam of reflected waves and employ convolution calculation for real-time adjustment of the reflection direction.
Article
Chemistry, Physical
Guanxuan Guo, Xueqian Zhang, Li Niu, Tong Wu, Xieyu Chen, Quan Xu, Jiaguang Han, Weili Zhang
Summary: We propose a programmable graphene metasurface based on the quantum effect analogue, electromagnetically induced transparency, which enables continuous amplitude and phase tuning of cross-polarized transmission in the terahertz (THz) regime. This programmable scheme allows flexible control over the diffraction angles and focal lengths of the transmitted THz beams, providing new inspirations for THz programmable metasurface devices.
Article
Materials Science, Multidisciplinary
Zhenkai Li, Chunyang Jiang, Kun Wang, Meng Liu, Chuanhao Li, Changdong Tian, Huiyun Zhang, Yuping Zhang
Summary: Multifunctional coding metasurfaces are a current research focus in highly integrated terahertz modulators. This study proposed a tunable chiral metasurface based on a Dirac semimetal (DSM) and demonstrated its multifunctional application in the terahertz region through coding. The chiral metasurface exhibited strong chirality and circular dichroism (CD) of up to 0.72 at 2.31 THz. By combining with the Pancharatnam-Berry (PB) phase, the metasurface enabled wideband switchable terahertz vortex beam generation, arbitrary angular deflection tuning, and multi-beam splitting. Switchable near-field imaging applications were also developed. The results have promising applications in terahertz high-data-capacity communication systems, multi-target information transmission, and controlled near-field imaging.
RESULTS IN PHYSICS
(2023)
Article
Optics
Hui Li, Chenglong Zheng, Hang Xu, Jie Li, Chunyu Song, Fan Yang, Jitao Li, Wei Shi, Yating Zhang, Jianquan Yao
Summary: In this study, an all-graphene geometric metasurface operating in the terahertz band is proposed and investigated. It can generate focused scalar vortex beams with polarization-independent properties by introducing a superposition of two helical phases. By embedding polarization modulation, multiple focused vortices with inhomogeneous polarization properties can be generated. The proposed design scheme has a greater degree of freedom and can find potential applications in meta-optics, high-tolerance edge imaging, and high-capacity optical communications.
OPTICS AND LASER TECHNOLOGY
(2023)
Review
Materials Science, Multidisciplinary
Yuyu LI, Mathan Ramaswamy Krisshnamurthi, Weijun Luo, Anna K. Swan, Xi Ling, Roberto Paiella
Summary: Graphene metasurfaces with active tunability are a promising candidate for terahertz wavelength optics. This review summarizes recent research on the development of tunable graphene metasurfaces for wavefront shaping and light emission at terahertz frequencies. Different design strategies and solutions for constituent meta-units are presented. The development of these devices is discussed, including the challenges and proposed solutions. The resulting metasurface technology is expected to have a significant impact on a wide range of THz device applications.
OPTICAL MATERIALS EXPRESS
(2022)
Article
Physics, Applied
Susan Fallah, Kasra Rouhi, Ali Abdolali
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2020)
Article
Optics
Roya Kargar, Kasra Rouhi, Ali Abdolali
OPTICS COMMUNICATIONS
(2020)
Article
Engineering, Electrical & Electronic
Hamid Rajabalipanah, Ali Abdolali, Kasra Rouhi
IEEE JOURNAL ON EMERGING AND SELECTED TOPICS IN CIRCUITS AND SYSTEMS
(2020)
Article
Nanoscience & Nanotechnology
Hamid Rajabalipanah, Kasra Rouhi, Ali Abdolali, Shahid Iqbal, Lei Zhang, Shuo Liu
Correction
Multidisciplinary Sciences
Ali Momeni, Kasra Rouhi, Hamid Rajabalipanah, Ali Abdolali
SCIENTIFIC REPORTS
(2021)
Article
Physics, Applied
Kasra Rouhi, Robert Marosi, Tarek Mealy, Ahmed F. Abdelshafy, Alexander Figotin, Filippo Capolino
Summary: The study focuses on the interaction between a linear electron beam and a guided electromagnetic wave in the context of exceptional points of degeneracy (EPD) supported by the system. A new model is proposed to describe this interaction in a linear beam traveling wave tube (TWT). The characteristics of EPDs and the sensitivity of the TWT-system to changes in electron velocity near an EPD are investigated using the augmented model.
APPLIED PHYSICS LETTERS
(2021)
Article
Chemistry, Physical
Ali Momeni, Kasra Rouhi, Romain Fleury
Summary: This paper presents reconfigurable graphene-based multilayers for spatiotemporal analog signal and image processing, demonstrating a switchable analog computing paradigm and simultaneous parallel spatiotemporal analog computing. The spatial-and temporal-frequency responses are engineered for integrated functionalities by selecting a proper external voltage for graphene monolayers, showing promising developments in analog computing.
Article
Engineering, Electrical & Electronic
Kasra Rouhi, Seyed Ehsan Hosseininejad, Sergi Abadal, Mohsen Khalily, Rahim Tafazolli
Summary: Digital metasurfaces engineered with graphene have addressed limitations in controlling electromagnetic devices in the THz band, allowing direct modulation of amplitude and phase with digital information. This enables a multi-channel high-speed communication system and the construction of a three-dimensional wireless agile interconnection, providing a new architecture for modern communications.
JOURNAL OF LIGHTWAVE TECHNOLOGY
(2021)
Article
Optics
Kasra Rouhi, Ali Abdolali, Susan Fallah
Summary: The research proposes a wide-band and low-scattering metasurface array in the THz spectrum, utilizing graphene square patches with different DC bias voltages to combine diffusion and absorption functionalities. The optimization strategy of chemical potential allows for real-time manipulation of reflected beams, leading to reduced energy of reflected waves in a wide spectrum range.
Article
Physics, Fluids & Plasmas
Tarek Mealy, Robert Marosi, Kasra Rouhi, Filippo Capolino
Summary: We propose an analytical method to calculate the wavenumbers and electric fields of space-charge-wave eigenmodes in a two-stream electron beam. The beam consists of a solid inner cylindrical stream and a coaxial outer annular stream, enclosed within a cylindrical metallic tunnel. Our method extends Ramo's analytical model to account for the interaction between the two streams and the beam-tunnel wall. It is suitable for modeling the complex wavenumbers associated with the two-stream instability and plasma frequency reduction effects in vacuum electronic amplifiers and other devices.
IEEE TRANSACTIONS ON PLASMA SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
Alireza Nikzamir, Kasra Rouhi, Alexander Figotin, Filippo Capolino
Summary: This paper studies exceptional points of degeneracy (EPD) in various circuit configurations and analyzes their high sensitivity to changes in resistance, capacitance, and inductance. The resonance frequency is also found to be highly sensitive to perturbations. The stability and instability conditions for these configurations are investigated, and the effect of nonlinear gain in PT-symmetry circuits is explored.
EPJ APPLIED METAMATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Kasra Rouhi, Alireza Nikzamir, Alexander Figotin, Filippo Capolino
Summary: Exceptional points of degeneracy (EPD) can greatly enhance the sensitivity of circuits. We demonstrate various configurations of coupled LC resonators via a gyrator that support second and third-order EPDs. Perturbations in a second-order EPD gyrator-based circuit lead to two real-valued frequencies shifted from the EPD frequency, following a square root law, in contrast to complex-valued perturbed resonances in Parity-Time (PT) symmetric circuits. We show different methods to achieve stable EPD, unstable EPD with imaginary frequency, and EPD with real frequency using an asymmetric gyrator. The Puiseux fractional power series expansion reveals the occurrence of EPDs and the circuit's sensitivity to perturbations. These findings open up possibilities for new high-sensitive devices that can detect physical, chemical, or biological changes.
EPJ APPLIED METAMATERIALS
(2022)
Article
Optics
Kasra Rouhi, Alireza Nikzamir, Alexander Figotin, Filippo Capolino
Summary: In this study, we demonstrate the existence of an exceptional point of degeneracy (EPD) with purely real eigenfrequency in a circuit consisting of two unstable LC resonators coupled via a gyrator. Each resonator exhibits a purely imaginary resonance frequency when not coupled to the other resonator via the gyrator. By imposing external perturbation on the system, we analytically show that the resonance frequency response of the circuit follows a square-root dependence on perturbation, which has potential sensor applications.
Proceedings Paper
Engineering, Electrical & Electronic
A. Nikzamir, K. Rouhi, A. Figotin, F. Capolino
Summary: The proposed high-sensitive circuit scheme is based on EPD, which combines two LC resonators with a gyrator. The conditions for obtaining EPDs in the circuit and the typical bifurcation diagram demonstrating the extreme sensitivity of the circuit operating at an EPD are presented. The high sensitivity induced by an EPD can be utilized for the development of a new generation of high-sensitive sensors.
2021 FIFTEENTH INTERNATIONAL CONGRESS ON ARTIFICIAL MATERIALS FOR NOVEL WAVE PHENOMENA (METAMATERIALS)
(2021)
Article
Engineering, Electrical & Electronic
Kasra Rouhi, Hamidreza Kazemi, Alexander Figotin, Filippo Capolino
IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS
(2020)