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

Metasurfaces present high capabilities for wavefront tailoring. Classical metasurfaces composed of densely packed meta-atoms with local electromagnetic response show limitations in terms of efficiency. Here, we present and discuss the design of sparse metasurfaces composed of only few elements with strong electromagnetic non-locality. Sparse metasurfaces of arbitrary geometry are designed and validated at microwave frequencies for antenna applications.

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Sparse Metasurface: Design and Implementation

A broadband planar reflective metasurface is designed to act as reflector for antenna applications. The phase profile of a parabolic reflector is engineered by judiciously controlling the geometrical dimensions of the constituting unit cells of the planar metasurface. A circularly-polarized low-profile flattened broadband parabolic reflector antenna is then designed by using a patch antenna as primary source. The antenna design is numerically simulated and results show a highly directive beam over a wide frequency band.

Circularly-Polarized Broadband Planar Parabolic Reflector Antenna

Metagratings with zero load impedance are proposed to achieve efficient beam splitting. Different from previously proposed metagratings that require specific capacitive and/or inductive structures to achieve load impedance, the metagrating proposed here consists solely of simple microstrip-line structures. Such a structure overcomes the implementation constraints such that low-cost fabrication technology can be applied for metagratings operating at higher frequencies. The detailed theoretical design procedure is presented together with numerical optimizations to achieve the specific design parameters. Finally, several reflection-type beam-splitting devices with different pointing angles are designed, simulated, and experimentally measured. The results show very high performance at 30 GHz, paving the way to simple and low-cost printed circuit board (PCB) metagratings at millimeter-wave and higher frequencies.

Efficient beam splitting using zero-load-impedance metagratings.

An enantiomeric flexible metasurface based detector with highly sensitivity is designed for detections in terahertz. The sensitive property primarily is based on electromagnetically induced reflection (EIR) response of a bilayered enantiomeric split Zs (BESZs) structure, which arises from dark mode resonances directly excited by $45^{\circ}$ incident waves. The reflection amplitude of EIR resonance with high quality factor is highly sensitive to surrounding environment. By setting splits, the sensitivity of EIR resonance can be further improved slightly. The sensing performance of proposed detector was evaluated by different thickness of germanium in simulation, and the results show that its reflection amplitude difference can reach about 0.3 even for 10 nm thickness of germanium, which demonstrates the functionality and great potential of enantiomeric structures in sensing and detection.

Direct dark mode excitation of electromagnetically induced reflection effect in enantiomer-based metasurface and its application in terahertz detection

We revisit the engineering of metasurfaces displaying sharp spectral features and conventionally relying on electromagnetically induced transparency resulting from Fano-type interference between dark and bright resonant elements. The aim of the developed approach based on symmetry considerations is to show that electromagnetically induced transparency and dark mode excitation are not necessarily associated. We bring theoretical and experimental evidence in the microwave domain that electromagnetically induced transparency and dark mode excitation can be achieved in an independent manner by using distinctly different mechanisms. The use of these distinctly different mechanisms provides higher flexibility for metasurfaces engineering and results in a great improvement of their spectral performances.

Shah Nawaz Burokur

Papers

Sparse Metasurface: Design and Implementation

Circularly-Polarized Broadband Planar Parabolic Reflector Antenna

Efficient beam splitting using zero-load-impedance metagratings.

Direct dark mode excitation of electromagnetically induced reflection effect in enantiomer-based metasurface and its application in terahertz detection

Dark-Mode Characteristics of Metasurfaces Engineered by Symmetry Matching of Resonant Elements and Electromagnetic Fields