다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The importance of the Fano resonance concept is recognized across multiple fields of physics. In this Review, Fano resonance is explored in the context of optics, with particular emphasis on dielectric nanostructures and metasurfaces. Rapid progress in photonics and nanotechnology brings many examples of resonant optical phenomena associated with the physics of Fano resonances, with applications in optical switching and sensing. For successful design of photonic devices, it is important to gain deep insight into different resonant phenomena and understand their connection. Here, we review a broad range of resonant electromagnetic effects by using two effective coupled oscillators, including the Fano resonance, electromagnetically induced transparency, Kerker and Borrmann effects, and parity–time symmetry breaking. We discuss how to introduce the Fano parameter for describing a transition between two seemingly different spectroscopic signatures associated with asymmetric Fano and symmetric Lorentzian shapes. We also review the recent results on Fano resonances in dielectric nanostructures and metasurfaces.

Fano resonances in photonics

13. 벼잎선충의 약제처리 방법별 방제 효과

Resonance conditions for a substrate-superstrate printed antenna geometry which allow for large antenna gain are presented. Asymptotic formulas for gain, beamwidth, and bandwidth are given, and the bandwidth limitation of the method is discussed. The method is extended to produce narrow patterns about the horizon, and directive patterns at two different angles.

Gain enhancement methods for printed circuit antennas

A metasurface (MS) used to convert the linearly polarized (LP) signal from a source antenna into a circularly polarized (CP) signal is proposed and studied. The MS consists of 16 unit cells arranged in a 4 × 4 layout. Each unit cell is a rectangular loop with a diagonal microstrip. By placing close to a source antenna, the MS converts the LP signal generated from the source antenna into a CP signal. Two source antennas (patch and slot antennas) are used for studies. The source antenna together with the MS is here called a MS antenna. A total of four low-profile MS antennas operating at the frequency of about 2.45 GHz are designed using computer simulation. For verification of simulation results, the MS antennas are fabricated and measured. Simulated and measured results show good agreements. Results show that the MS antennas have substantially better performances, in terms of gain, return-loss bandwidth (RLBW), axial-ratio bandwidth (ARBW) and radiation pattern, than the source antennas. Moreover, the ARBW of the MS antennas is mainly determined by the MS.

Linear-to-Circular Polarization Conversion Using Metasurface

A metamaterial-based low profile antenna is presented in the 8-12 GHz frequency range (X-band). The antenna is designed in a parallel-plate TEM waveguide configuration. A planar metamaterial-based Luneburg lens and a Vivaldi antenna that illuminates the latter lens are embedded inside the TEM waveguide. The focusing condition of the lens, requiring a gradient refractive index is achieved through the use of complementary non-resonant metamaterial structures. Numerical simulations are performed to determine the suitable unit cells geometry with respect to the wave launcher. A prototype has been fabricated using standard printed circuit board techniques and has been measured in an anechoic chamber. A good qualitative agreement is observed between simulations and experiments. The proposed planar antenna presents good focusing properties over the X-band frequency range.

X-band metamaterial-based Luneburg lens antenna

Spin-selective metamirrors consisting of planar meta-atoms are able to reflect tailored incident circularly polarized waves either in similar or opposite handedness while absorbing the other handedness of spin-wave. In this paper, we propose a novel design of a metamirror exhibiting both spin-selective absorption and phase modulation properties. A chiral metamirror with asymmetric split-ring resonators is proposed to achieve spin-selective reflection/absorption. Meanwhile, a geometric phase is introduced to provide a full 2π reflection-phase coverage. Theoretical results indicate a maximum absorption of 99.34% for left-handed circularly polarized (LHCP) wave, while keeping the reflection of right-handed circularly polarized (RHCP) higher than 91% without changing the handedness. By virtue of the above merits, we implement a metadevice that can convert incident RHCP waves into vortex waves with identical handedness from 8.3 to 10.3 GHz and absorb incident LHCP waves at its operation band. For experimental verification, a proof-of-concept metamirror is fabricated and experimentally characterized, which reveals the spin-dependent bifunctional performances of the proposed metamirror. Our strategy provides a promising route for the realization of spin-selective planar devices in wireless communications.

Chirality-intrigged Spin-selective Metasurface and Applications in Generating Orbital Angular Momentum

A broadband metamaterial-based low profile antenna is presented in the 8-12 GHz frequency band. The antenna is composed of a parallel-plate TEM waveguide embedding a planar gradient index Luneburg lens and a slot Vivaldi antenna that illuminates the latter lens. The focusing condition of the lens, requiring a gradient refractive index is achieved through the use of complementary non-resonant metamaterial structures. Numerical simulations are performed to determine the suitable unit cells geometry with respect to the wave launcher. A prototype fabricated using standard printed circuit board techniques has been measured in an anechoic chamber. A good qualitative agreement is observed between simulations and experiments. The proposed planar antenna presents good focusing properties.

Broadband low profile substrate-integrated antenna based on gradient index lens

An ultrathin metasurface is made reconfigurable through the use of unit cells incorporating voltage-controlled varactor diodes. The phase characteristics of each unit cell are individually controlled for reconfigurability mechanisms. Two main applications are proposed in the domain of microwave devices and antennas. The planar metasurface is illuminated by a primary source and is firstly used as reconfigurable reflector allowing beam steering performances and frequency agility. A second functionality is also demonstrated, where the metasurface is used as a reconfigurable polarizer. Measurements are performed on a fabricated prototype to validate the concept.

Reconfigurable Metasurface as Microwave Reflectors and Polarization Converters

A high-index dielectric radome seam is camouflaged with respect to a low-index dielectric radome panel by tuning the seam with carefully engineered metasurfaces. A transmission-line approach is used to model the metasurface-tuned seam and analytically retrieve the corresponding surface impedance, from which the unit-cell design is then tailored. Full-wave simulations and microwave antenna measurements performed on a proof-of-concept prototype validate the undesired scattering suppression effect in the case of normally and obliquely incident transverse electric and transverse magnetic wave illuminations. Robustness of the proposed solution to fabrication tolerances is also reported. The study presents metasurface-tuning as an easily implementable, frequency adjustable, and polarization insensitive solution to reduce the scattering of dielectric mechanical seams and improve the overall transparency performance of radome structures.

/pdf/metasurfaces-for-far-field-radiation-pattern-correction-of-3i3b0zfl.pdf

Shah Nawaz Burokur

Papers

X-band metamaterial-based Luneburg lens antenna

Chirality-intrigged Spin-selective Metasurface and Applications in Generating Orbital Angular Momentum

Broadband low profile substrate-integrated antenna based on gradient index lens

Reconfigurable Metasurface as Microwave Reflectors and Polarization Converters

Metasurfaces for Far-Field Radiation Pattern Correction of Antennas under Dielectric Seamed-Radomes