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 compact and small electric-size aperture directive broadband Luneburg lens antenna is presented. The substrate-integrated lens antenna is based on embedding a Vivaldi antenna source inside a parallel-plate waveguide to illuminate a Luneburg lens operating in X-band. The focusing condition of the lens, requiring a gradient refractive index, is achieved through the use of complementary nonresonant metamaterial structures. Numerical simulations are performed to determine the suitable unit cells geometry with respect to the wave launcher inserted into the parallel-plate waveguide. A prototype fabricated using standard printed circuit board techniques has been measured in an anechoic chamber. The electric field distribution inside the antenna system has also been explored using a two-dimensional near-field microwave scanning setup. A good qualitative agreement is observed between simulations and experiments. It has been shown from both far- and near-field measurements that the proposed planar antenna presents good focusing properties.

Compact Metamaterial-Based Substrate-Integrated Luneburg Lens Antenna

A simple model allowing us to predict beam steering characteristics in a Fabry-Perot (FP) cavity antenna is presented in this letter. The structure consists of a ground plane and a phase-modulated metasurface used as a partially reflective surface (PRS). The aim of this letter is to present a simple model that allows calculating the necessary phase modulation for a desired beam-steering angle. Furthermore, phase-modulated metasurfaces are designed by varying the PRS inductance, and the model is validated both numerically and experimentally on antennas designed to operate around 2.25 GHz.

Design of Phase-Modulated Metasurfaces for Beam Steering in Fabry–Perot Cavity Antennas

Metamaterials continue to change the way we think about manipulating light. For example, although conventional diffraction gratings are well-studied and widely used, only a few configurations (as in blazed gratings) allow efficient, accurate control of diffraction. The authors show that to construct arbitrary diffraction patterns, each propagating diffraction order requires $e\phantom{\rule{0}{0ex}}x\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}y$ two degrees of freedom, represented by structured ``wires'' (in a metamaterial, say). This important result solves an old problem of power management by a diffraction grating. From the physical point of view, it is achieved by accurately adjusting the optical near field scattered from a grating.

Constructing the Near field and Far field with Reactive Metagratings: Study on the Degrees of Freedom

Directive metamaterial-based subwavelength resonant cavity antennas – Applications for beam steering

A low-profile substrate-integrated lens antenna is designed using planar metamaterials for a broadband operation. The lens antenna is based on embedding a Vivaldi antenna source inside a parallel-plate waveguide to illuminate a half Maxwell fish-eye (HMFE) lens operating in X-band. The focusing condition of the lens, requiring a gradient refractive index is achieved through the use of complementary nonresonant metamaterial structures. Numerical simulations are performed to determine the suitable unit cells geometry with respect to the wave launcher inserted into the parallel-plate waveguide. The electric field distribution inside the antenna system has also been explored numerically. Far-field radiation patterns have been measured on a fabricated prototype in an anechoic chamber. It has been shown from both near- and far-field plots that the proposed planar antenna presents good focusing properties.

Shah Nawaz Burokur

Papers

Compact Metamaterial-Based Substrate-Integrated Luneburg Lens Antenna

Design of Phase-Modulated Metasurfaces for Beam Steering in Fabry–Perot Cavity Antennas

Constructing the Near field and Far field with Reactive Metagratings: Study on the Degrees of Freedom

Directive metamaterial-based subwavelength resonant cavity antennas – Applications for beam steering

Low-Profile Substrate-Integrated Lens Antenna Using Metamaterials