Transmission of Electromagnetic Waves through a Subwavelength Slit using a Reconfigurable Phase-Gradient Metasurface

Electromagnetic waves carrying an orbital angular momentum (OAM) are of great interest. However, most OAM antennas present disadvantages such as a complicated structure, low efficiency, and large divergence angle, which prevents their practical applications. So far, there are few papers and research focuses on the problem of the divergence angle. Herein, a metasurface antenna is proposed to obtain the OAM beams with a small divergence angle. The circular arrangement and phase gradient were used to simplify the structure of the metasurface and obtain the small divergence angle, respectively. The proposed metasurface antenna presents a high transmission coefficient and effectively decreases the divergence angle of the OAM beam. All the theoretical analyses and derivation calculations were validated by both simulations and experiments. This compact structure paves the way to generate OAM beams with a small divergence angle.

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A Thermal Tuning Meta-Duplex-Lens (MDL): Design and Characterization

Nanomaterials ◽

10.3390/nano10061135 ◽

2020 ◽

Vol 10 (6) ◽

pp. 1135 ◽

Cited By ~ 1

Author(s):

Ning Xu ◽

Yaoyao Liang ◽

Yuan Hao ◽

Min Mao ◽

Jianping Guo ◽

...

Keyword(s):

Phase Change ◽

Phase Change Material ◽

Electromagnetic Waves ◽

Incident Light ◽

Polarization State ◽

Transmission Efficiency ◽

Metallic State ◽

Phase Gradient ◽

Storage Devices ◽

Change Material

Multifunctional metasurfaces play an important role in the development of integrated optical paths. However, some of the realizations of current multifunctional metasurface devices depend on polarization selectivity, and others change the polarization state of the outgoing light. Here, based on vanadium dioxide (VO2) phase change material, a strategy to design a meta-duplex-lens (MDL) is proposed and numerical simulation calculations demonstrate that at low temperature (about 300 K), VO2 behaves as a dielectric so that the MDL can act as a transmission lens (transmission efficiency of 87.6%). Conversely, when VO2 enters the metallic state (about 355 K), the MDL has the ability to reflect and polymerize electromagnetic waves and works as a reflection lens (reflection efficiency of 85.1%). The dielectric waveguide and gap-surface plasmon (GSP) theories are used in transmission and reflection directions, respectively. In order to satisfy the coverage of the phase gradient in the range of 2π in both cases, we set the antenna as a nanopillar with a high aspect ratio. It is notable that, via symmetrical antennas acting in concert with VO2 phase change material, the polarization states of both the incident light and the outgoing light are not changed. This reversible tuning will play a significant role in the fields of imaging, optical storage devices, communication, sensors, etc.

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Optimization and Inverse-design Techniques for Metalens Synthesis

Applied Computational Electromagnetics Society ◽

10.47037/2020.aces.j.351136 ◽

2021 ◽

Vol 35 (11) ◽

pp. 1334-1335

Author(s):

Sawyer Campbell ◽

Eric Whiting ◽

Ronald Jenkins ◽

Pingjuan Werner ◽

Douglas Werner

Keyword(s):

Electromagnetic Waves ◽

High Performance ◽

Inverse Design ◽

Optical Systems ◽

Challenging Problem ◽

Phase Gradient ◽

Unit Cells ◽

Cell Components ◽

Meta Atom ◽

Design Techniques

Phase-gradient metasurfaces enable designers to tailor the behavior of electromagnetic waves at surfaces by exploiting the generalized form of Snell’s law. This ability has led to the investigation of metalenses which have the potential to significantly reduce the size, weight, and power (SWaP) of conventional optical systems. While traditional lenses are made from individual glasses, metalenses are comprised of patterned meta-atom unit Cells which are arranged in such a way so as to give the metalens its desired behavior. Therefore, any metalens’s performance is ultimately determined by that of its underlying unit cell components. However, designing meta-atoms that simultaneously achieve high performance over wide frequency bandwidths and fields-of-view is an extremely challenging problem that is best addressed with powerful optimization and inverse-design techniques.

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Broadband and high-efficiency accelerating beam generation by dielectric catenary metasurfaces

Nanophotonics ◽

10.1515/nanoph-2020-0057 ◽

2020 ◽

Vol 9 (9) ◽

pp. 2829-2837 ◽

Cited By ~ 2

Author(s):

Fei Zhang ◽

Qingyu Zeng ◽

Mingbo Pu ◽

Yanqin Wang ◽

Yinghui Guo ◽

...

Keyword(s):

Electromagnetic Waves ◽

High Efficiency ◽

Spectral Band ◽

Subwavelength Structures ◽

Self Healing ◽

Infrared Band ◽

Phase Gradient ◽

Beam Generation ◽

Large Phase ◽

Low Efficiency

AbstractSelf-accelerating beams show considerable captivating phenomena and applications owing to their transverse acceleration, diffraction-free and self-healing properties in free space. Metasurfaces consisting of dielectric or metallic subwavelength structures attract enormous attention to acquire self-accelerating beams, owing to their extraordinary capabilities in the arbitrary control of electromagnetic waves. However, because the self-accelerating beam generator possesses a large phase gradient, traditional discrete metasurfaces suffer from insufficient phase sampling, leading to a low efficiency and narrow spectral band. To overcome this limitation, a versatile platform of catenary-inspired dielectric metasurfaces is proposed to endow arbitrary continuous wavefronts. A high diffraction efficiency approaching 100% is obtained in a wide spectral range from 9 to 13 μm. As a proof-of-concept demonstration, the broadband, high-efficiency and high-quality self-accelerating beam generation is experimentally verified in the infrared band. Furthermore, the chiral response of the proposed metasurfaces enables the spin-controlled beam acceleration. Considering these superior performances, this design methodology may find wide applications in particle manipulation, high-resolution imaging, optical vortex generation, and so forth.

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1D and 2D phase gradient perforated dielectric reflective surfaces atmmWave

International Journal of Microwave and Wireless Technologies ◽

10.1017/s1759078717001337 ◽

2017 ◽

Vol 10 (4) ◽

pp. 446-452 ◽

Cited By ~ 1

Author(s):

Mustafa K. Taher Al-Nuaimi ◽

Wei Hong ◽

Xiqi Gao

Keyword(s):

Electromagnetic Waves ◽

Normal Incidence ◽

Electrical Conductor ◽

Wave Regime ◽

Phase Gradient ◽

Reflected Waves ◽

Dielectric Surfaces ◽

Full Wave ◽

Perfect Electrical Conductor ◽

Reflective Surfaces

This paper presents the design of all dielectric non-absorptive phase gradient reflective surfaces that can be used to manipulate the reflected electromagnetic waves at millimeter-wave regime. Compared with a bare perfect electrical conductor reflector which obeys the classical Snell's law of reflection, the presented design can effectively alter both the shape and level of the backscattered energy and thus radar cross section (RCS) reduction is achieved in the specular direction. One- and two-dimensional phase gradient reflective dielectric surfaces of phase change about 72° across their apertures are designed and their ability to manipulate the reflected waves under normal incidence are investigated both by means of full-wave simulations and experimentally tested for validation. More than 6 dB of specular RCS reduction is achieved from about 66.5–78.2 GHz.

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Single-layer phase gradient mmWave metasurface for incident angle independent focusing

Scientific Reports ◽

10.1038/s41598-021-92083-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Wonwoo Lee ◽

Semin Jo ◽

Kanghyeok Lee ◽

Hong Soo Park ◽

Junhyuk Yang ◽

...

Keyword(s):

Electromagnetic Waves ◽

High Performance ◽

Phase Distribution ◽

Focal Point ◽

Incident Angle ◽

Rapid Development ◽

Single Layer ◽

Phase Gradient ◽

Wave Focusing ◽

Practical Applications

AbstractMetasurfaces allow the rapid development of compact and flat electromagnetic devices owing to their capability in manipulating the wavefront of electromagnetic waves. Particularly, with respect to the metasurface lenses, wide operational bandwidth and wide incident angle behavior are critically required for practical applications. Herein, a single-layer phase gradient metasurface lens is presented to achieve millimeter-wave focusing at a focal point of 13 mm regardless of the incident angle. The proposed metasurface lens is fabricated by constructing subwavelength-thick (< λ/10) phase elements composed of two metallic layers separated by a single dielectric substrate that exhibits low-Q resonance properties and a wide phase modulation range with satisfactory transmissivity. By controlling the spatial phase distribution, the proposed metasurface lens successfully realises effective wavefront manipulation properties and high-performance electromagnetic-wave-focusing characteristics over a wide operating frequency range from 35 to 40 GHz with incident angle independency up to 30°.

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Seti Space Missions

International Astronomical Union Colloquium ◽

10.1017/s0252921100015372 ◽

1997 ◽

Vol 161 ◽

pp. 761-776 ◽

Cited By ~ 1

Author(s):

Claudio Maccone

Keyword(s):

Electromagnetic Waves ◽

Space Missions ◽

Gravitational Lens ◽

The Sun ◽

Space Antenna ◽

Focal Distance ◽

Large Space ◽

The Earth ◽

Space Antennas ◽

New Space

AbstractSETI from space is currently envisaged in three ways: i) by large space antennas orbiting the Earth that could be used for both VLBI and SETI (VSOP and RadioAstron missions), ii) by a radiotelescope inside the Saha far side Moon crater and an Earth-link antenna on the Mare Smythii near side plain. Such SETIMOON mission would require no astronaut work since a Tether, deployed in Moon orbit until the two antennas landed softly, would also be the cable connecting them. Alternatively, a data relay satellite orbiting the Earth-Moon Lagrangian pointL2would avoid the Earthlink antenna, iii) by a large space antenna put at the foci of the Sun gravitational lens: 1) for electromagnetic waves, the minimal focal distance is 550 Astronomical Units (AU) or 14 times beyond Pluto. One could use the huge radio magnifications of sources aligned to the Sun and spacecraft; 2) for gravitational waves and neutrinos, the focus lies between 22.45 and 29.59 AU (Uranus and Neptune orbits), with a flight time of less than 30 years. Two new space missions, of SETI interest if ET’s use neutrinos for communications, are proposed.

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Microwaves: Application in Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100158248 ◽

1990 ◽

Vol 48 (3) ◽

pp. 140-141

Author(s):

Anthony S-Y Leong ◽

David W Gove

Keyword(s):

Electron Microscopy ◽

Light Microscopy ◽

Chemical Reactions ◽

Electromagnetic Waves ◽

Tissue Fixation ◽

Primary Method ◽

Dipolar Molecules ◽

Wide Range ◽

Time Required ◽

Cryostat Sections

Microwaves (MW) are electromagnetic waves which are commonly generated at a frequency of 2.45 GHz. When dipolar molecules such as water, the polar side chains of proteins and other molecules with an uneven distribution of electrical charge are exposed to such non-ionizing radiation, they oscillate through 180° at a rate of 2,450 million cycles/s. This rapid kinetic movement results in accelerated chemical reactions and produces instantaneous heat. MWs have recently been applied to a wide range of procedures for light microscopy. MWs generated by domestic ovens have been used as a primary method of tissue fixation, it has been applied to the various stages of tissue processing as well as to a wide variety of staining procedures. This use of MWs has not only resulted in drastic reductions in the time required for tissue fixation, processing and staining, but have also produced better cytologic images in cryostat sections, and more importantly, have resulted in better preservation of cellular antigens.

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