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active metasurface in reflection manner for generation of reconfigurable OAM vortex beams

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Journal of Information and Intelligence

Journal of Information and Intelligence 2023年第3期1卷 197-206页

作者： Yunfei Liu Yueyi Yuan Qun Wu Kuang Zhang The School of Electronic and Information Engineering Harbin Institute of TechnologyHarbin 150001China

In this paper,we proposed an active metasurface in reflection manner that can generate reconfigurable OAM vortex beams with high purity in the X-band.The metasurface has a high reflectance of 0.94 and achieves a phase coverage of 320between 9.8 GHz and 11 GHz.Then,by encoding the phase distribution of the meta-atoms,various OAM vortex beams including 1,2,3,and 4 orders are generated,where the purity of all modes can be above 70%.Moreover,the metasurface can also deflect the OAM beam with a certain angle while maintaining high purity,which can be applied to reduce the influence of the alignment deviation between transmitting and receiving antennas during the communication processes.As a validation,the metasurface composed of 30×30 meta-atoms is fabricated and measured.Both simulation and measurement results demonstrate the capability of the proposed metasurface to generate reconfigurable OAM beams with high purity,indicating the application potentials of proposed meta-devices in future OAM communications.

关键词： Orbital angular momentum(OAM) active metasurface Reconfigurable High purity X-band

active spintronic-metasurface terahertz emitters with tunable chirality

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Advanced Photonics 2021年第5期3卷 52-61页

作者： Changqin Liu Shunjia Wang Sheng Zhang Qingnan Cai Peng Wang Chuanshan Tian Lei Zhou Yizheng Wu Zhensheng Tao Fudan University Department of Physics and State Key Laboratory of Surface PhysicsShanghaiChina Shanghai Research Center for Quantum Sciences ShanghaiChina

The ability to generate and manipulate broadband chiral terahertz waves is essential for applications in material imaging,terahertz sensing,and diagnosis.It can also open up new possibilities for nonlinear terahertz spectroscopy and coherent control of chiral molecules and magnetic materials.The existing methods,however,often suffer from low efficiency,narrow bandwidth,or poor flexibility.Here,we propose a novel type of laser-driven terahertz emitters,consisting of metasurface-patterned magnetic multilayer heterostructures,that can overcome the shortcomings of the conventional approaches.Such hybrid terahertz emitters combine the advantages of spintronic emitters for being ultrabroadband,efficient,and highly flexible,as well as those of metasurfaces for the powerful control capabilities over the polarization state of emitted terahertz waves on an ultracompact platform.Taking a stripe-patterned metasurface as an example,we demonstrate the efficient generation and manipulation of broadband chiral terahertz waves.The ellipticity can reach>0.75 over a broad terahertz bandwidth(1 to 5 THz),representing a high-quality and efficient source for few-cycle circularly polarized terahertz pulses with stable carrier waveforms.Flexible control of ellipticity and helicity is also demonstrated with our systematic experiments and numerical simulations.We show that the terahertz polarization state is dictated by the interplay between laser-induced spintronic-origin currents and the screening charges/currents in the metasurfaces,which exhibits tailored anisotropic properties due to the predesigned geometric confinement effects.Our work opens a new pathway to metasurface-tailored spintronic emitters for efficient vector-control of electromagnetic waves in the terahertz regime.

关键词： chiral terahertz generation active metasurface time-domain terahertz spectroscopy

Tunable metasurfaces towards versatilemetalenses and metaholograms:a review

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Advanced Photonics 2022年第2期4卷 7-22页

作者： Jaekyung Kim Junhwa Seong Younghwan Yang Seong-Won Moon Trevon Badloe Junsuk Rho Pohang University of Science and Technology Department of Mechanical EngineeringPohangRepublic of Korea Pohang University of Science and Technology Department of Chemical EngineeringPohangRepublic of Korea POSCO–POSTECH–RIST Center for Flat Optics and Metaphotonics PohangRepublic of Korea

metasurfaces have attracted great attention due to their ability to manipulate the phase,amplitude,and polarization of light in a compact form.Tunable metasurfaces have been investigated recently through the integration with mechanically moving components and electrically tunable elements.Two interesting applications,in particular,are to vary the focal point of metalenses and to switch between holographic images.We present the recent progress on tunable metasurfaces focused on metalenses and metaholograms,including the basic working principles,advantages,and disadvantages of each working mechanism.We classify the tunable stimuli based on the light source and electrical bias,as well as others such as thermal and mechanical modulation.We conclude by summarizing the recent progress of metalenses and metaholograms,and providing our perspectives for the further development of tunable metasurfaces.

关键词： tunable metasurface active metasurface reconfigurable metasurface multifunctional metahologram varifocal metalens

Dual-polarized and real-time reconfigurable metasurface absorber with infrared-coded remote-control system

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Nano Research 2022年第8期15卷 7498-7505页

作者： Jiangyong Liu Yuping Duan Tuo Zhang Lingxi Huang Huifang Pang Key Laboratory of Solidification Control and Digital Preparation Technology(Liaoning Province) School of Materials Science and EngineeringDalian University of TechnologyDalian 116085China

The reconfigurable metasurfaces which can regulate the microwave absorption performance at the sub wavelength scale provide a possibility to construct intelligent stealth system.However,the existing reconfigurable-metasurface-based absorbers seriously limit the medium and long-distance regulation in practical application due to the complex circuit path and regulation mode.Here,an infrared-coded dual-polarized metasurface absorber(IDMA)with remote-control mode was proposed,which realized the realtime dynamic regulation of the intensity and frequency range of absorption peaks by combining the infrared-coding remotecontrol technology with the active metasurface absorber.The proposed remote-control system can switch the 8-bit binary coding sequences stored in the microcontroller unit(MCU)by an infrared transceiver,so as to regulate the state of active devices under X-and Y-polarizations,respectively.The experimental results showed that the reflection/absorption responses can be regulated by switching different binary codes,and the reflection loss(RL)can be tuned below−7.5 dB(absorptivity over 82%)in wide range of 6.20–18 GHz.Furthermore,the corresponding equivalent circuit model was established and the distributions of surface current and electric field were analyzed to elucidate the dynamic reconfigurable mechanism of the metasurface absorber.The proposed IDMA,which combines intelligent electronic technology with active metasurface absorber,creatively realizes the remote control of active metasurface absorber and opens up a new way for the stealth technology of smart absorber in the future.

关键词： microwave absorption active metasurface reflection/absorption infrared-coded remote-control real-time dynamic control

active metasurfaces for manipulatable terahertz technology

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Chinese Physics B 2020年第9期29卷 92-104页

作者：吴静远徐晓峰韦联福 Photonics Laboratory and Institute of Functional Materials College of ScienceDonghua UniversityShanghai 201620China Information Quantum Technology Laboratory School of Information Science and TechnologySouthwest Jiaotong UniversityChengdu 610031China

metasurface is a kind of two-dimensional metamaterial with specially designed sub-wavelength unit cells.It consists of single-layer or few-layer stacks of planar structures and possesses certain superior abilities to manipulate the propagating electromagnetic waves,including the terahertz(THz)ones.Compared with the usual passive THz metasurfaces whose optical properties are difficult to be controlled after fabrication,the active materials are highly desirable to enable dynamic and tunable control of THz waves.In this review,we briefly summarize the progress of active THz metasurfaces,from their physical mechanisms on carrier concentration modulations,phase transitions,magneto-optical effects,etc.,for various possible THz applications mainly with low-dimensional materials,vanadium dioxide films,and superconductors.

关键词： metamaterial active metasurface terahertz wave modulations

High-efficiency reflection phase tunable metasurface at near-infrared frequencies

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Chinese Physics B 2021年第5期30卷 650-654页

作者：李策朱维杜硕李俊杰顾长志 Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China School of Physical Sciences CAS Key Laboratory of Vacuum PhysicsUniversity of Chinese Academy of SciencesBeijing 100049China Key Laboratory of Space Applied Physics and Chemistry Ministry of Education and Department of Applied PhysicsSchool of ScienceNorthwestern Polytechnical UniversityXi'an 710129China Songshan Lake Materials Laboratory Dongguan 523808China Collaborative Innovation Center of Quantum Matter Beijing 100871China

The realization of active modulation of reflection phase based on metasurfaces is of great significance for flexible control of electromagnetic wavefront,which makes metasurfaces have practical application values in polarization conversion,beam steering,metalens,etc.In this paper,a reflection phase tunable gap-surface plasmon(GSP)metasurface based on phase change materials Ge_(2)Sb_(2)Te_(5)(GST)is designed and experimentally demonstrated.By virtue of the characteristics of large permittivities difference before and after GST phase transition and the existence of stable intermediate states,the continuous modulation of near-infrared reflection phase larger than 200°has been realized.At the same time,through the reasonable design of the structure sizes,the reflection has been maintained at about 0.4 and basically does not change with the GST phase transition,which improved the working efficiency of the metasurface significantly.In addition,the coupled-mode theory(CMT)is introduced to make a full analysis of the modulation mechanism of the reflection phase,which proves that the phase transition of GST can induce the transition of metasurface working state from overcoupling mode to critical coupling mode.The improvement of the metasurface working efficiency has practical values for wavefront modulation.

关键词： active metasurface phase change materials phase modulation