Metamaterial

In-depth analysis of the theory, properties and description of the most potential technological applications of metamaterials for the realization of novel devices such as subwavelength lenses, invisibility cloaks, dipole and reflector antennas, high frequency telecommunications, new designs of bandpass filters, absorbers and concentrators of EM waves etc. In order to create a new devices it is necessary to know the main electrodynamical characteristics of metamaterial structures on the basis of which the device is supposed to be created. The electromagnetic wave scattering surfaces built with metamaterials are primarily based on the ability of metamaterials to control the surrounded electromagnetic fields by varying their permeability and permittivity characteristics. The book covers some solutions for microwave wavelength scales as well as exploitation of nanoscale EM wavelength such as visible specter using recent advances of nanotechnology, for instance in the field of nanowires, nanopolymers, carbon nanotubes and graphene. Metamaterial is suitable for scholars from extremely large scientific domain and therefore given to engineers, scientists, graduates and other interested professionals from photonics to nanoscience and from material science to antenna engineering as a comprehensive reference on this artificial materials of tomorrow

Tatsuo Itoh : discurs llegit a la cerimònia d'investidura celebrada a la Sala d'Actes del Rectorat el dia 14 d'octubre de l'any 2015

Tatsuo Itoh va ser investit doctor honoris causa per la UAB per les seves rellevants contribucions a l'enginyeria de radiofreqüència/microones i de les telecomunicacions.Nomenament 19/03/2015. A proposta de l'Escola d'Enginyeria. L'acte d'investidura va tenir lloc el 14 d'octubre de 201

Design and realization for radar cross section reduction of patch antennas using shorted stubs metamaterial absorbers

This thesis is devoted to analyzing of the Radar Cross Section (RCS) of rectangular patch antenna using Metamaterial Absorber (MMA) and the analysis of its reducing techniques. The addressed theme has a great complexity and it covers various areas that include designing and optimization of target geometrical model of rectangular patch antenna structures and making it compatible with respect to metamaterial geometry. Analyses have been made to optimize and validate the structure performances that include numerical methods for electromagnetic field computation, MMA behavior, characterization, extraction of parameters, antenna radiation performance analyses, simulation, fabrication, testing, and optimization with back validating the designs. The MMA structure finds its applications in antenna designing for the reduction of Monostatic and Bistatic RCS in stealth platform for lower detectable objects. However, there is still more emphasis needed to devote for in-band frequency response for low RCS of the antenna. Therefore, making these assumptions, we have been proposing novel designs of single-band, dual-band, and triple-band MMA structures. These structures provide significant scattering characteristics and offering flexibility to the designer to control and tune the resonant frequency, based on the specific applications as compared to that of the other MMAs in the microwave regime of the Electromagnetic (EM) spectrum. To explore the research scope, a three dimensional Frequency Selective Surface (FSS) structure has been analyzed and its simulation responses with respect to parametric analyses have been made. The research investigation further extended to Electronic Band Gap (EBG) Structure and Defected Ground Structure (DGS). A hybrid structure of patch antenna is proposed and designed for an inset feed rectangular microstrip patch antenna operating at 2.45 GHz in the Industrial, Scientific, and Medical (ISM) band. This hybrid structure claims the size reduction, bandwidth, and gains enhancement. The main focus of this research work is limited to determine the potential and practical feasibility of MMA’s to enhance the stealth performance of rectangular patch antennas. For this purpose, Monostatic and Bistatic RCS simulation and measurements are carried out in an anechoic chamber and practical methods for Radar Cross Section reduction are discussed and analyzed

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Inverse Design of Three-Dimensional Frequency Selective Structures and Metamaterials using Multi-Objective Lazy Ant Colony Optimization

With the rise of big data and the “internet of things,” wireless signals permeate today’s environment more than ever before. As the demand for information and security continues to expand, the need for filtering a crowded signal space will become increasingly important. Although existing devices can achieve this with additional components, such as in-line filters and low noise amplifiers, these approaches introduce additional bulk, cost and complexity. An alternative, low-cost solution to filtering these signals can be achieved through the use of Frequency Selective Surfaces (FSSs), which are commonly used in antennas, polarizers, radomes, and intelligent architecture. FSSs typically consist of a doubly-periodic array of unit cells, which acts as a spatial electromagnetic filter that selectively rejects or transmits electromagnetic waves, based on the unit cell’s geometry and material properties. Unlike traditional analog filters, spatial filters must also account for the polarization and incidence angle of signals; thus, an ideal FSS maintains a given frequency response for all polarizations and incidence angles. Traditional FSS designs have ranged from planar structures with canonical shapes to miniaturized and multi-layer designs using fractals and other space-filling geometries. More recently, FSS research has expanded into three-dimensional (3D) designs, which have demonstrated enhanced fields of view over traditional planar and multi-layer designs. To date, nearly all FSSs still suffer from significant shifts in resonant frequencies or onset of grating lobes at incidence angles beyond 60 degrees in one or more polarizations. Additionally, while recent advances in additive manufacturing techniques have made fully 3D FSS designs increasingly popular, design tools to exploit these fabrication methods to develop FSSs with ultra-wide Fields of View (FOV) do not currently exist. In this dissertation, a Multi-Objective Lazy Ant Colony Optimization (MOLACO) scheme will be introduced and applied to the problem of 3D FSS design for extreme FOVs. The versatility of this algorithm will further be demonstrated through application to the design of meander line antennas, optical antennas, and phase-gradient metasurfaces

Fiber Optic Sensors and Fiber Lasers

The optical fiber industry is emerging from the market for selling simple accessories using optical fiber to the new optical-IT convergence sensor market combined with high value-added smart industries such as the bio industry. Among them, fiber optic sensors and fiber lasers are growing faster and more accurately by utilizing fiber optics in various fields such as shipbuilding, construction, energy, military, railway, security, and medical.This Special Issue aims to present novel and innovative applications of sensors and devices based on fiber optic sensors and fiber lasers, and covers a wide range of applications of optical sensors. In this Special Issue, original research articles, as well as reviews, have been published

복소, 무질서 및 광학적 비선형 퍼텐셜에서의 대칭성 붕괴를 통한 빛의 흐름 제어

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2015. 8. 박남규.매질 내 빛의 흐름은 통상적으로 거시적 맥스웰 방정식에 의해 정의된다. 동질성 및 등방성을 가지고, 선형적이며, 시간에 대해 일정한 광학 매질 변수를 갖는 이상적인 매질에서는 광파의 양상이 페르마의 원리의 직접적인 예인 진동하는 전자기장의 직진 형태로, 간단하며 직관적이다. 이러한 평면파적 특성은 기하 광학의 바탕이며, 슈뢰딩거 방정식 형태의 파동 방정식이 갖는 다양한 대칭성 (병진 대칭, 키랄 대칭, 에르미트 대칭, 로렌츠 대칭 및 시간 반전 대칭)의 보존에서 그 원리을 찾을 수 있다. 렌즈, 거울 및 프리즘과 같은 고전적인 방식에서조차, 빛의 흐름을 조절키 위해서는 일부 광학적 대칭성의 붕괴를 필요로 한다. 비균질 매질에서의 병진 대칭의 붕괴는 굴절, 반사, 회절과 같은 산란 기반 빛 제어를 위한 고전적인 방법이다. 전파 시의 빛 에너지의 소모 또는 증폭은 파동 방정식의 비에르미트 헤밀토니안에 의해 정량화된다. 키랄 분자로 이루어진 매질은 광학 활성, 즉 빛의 편광을 돌릴 수 있도록 한다. 천문학에서 별 및 은하 움직임의 관찰에 이용되는 광학적 도플러 효과는 로렌츠 대칭성을 붕괴시키는 광원의 시간에 따른 변화에 기반한다. 비직관적인 이론적 결과물 및 향상된 공정 기술을 포함하는 광학 분야의 최근 성과들은 이제 비고전적인 빛의 흐름을 이끌어내기 위한 광학적 퍼텐셜 제어의 새로운 영역을 개척하고 있다. 메타 물질 개념과 연계된 나노 스케일 기술은 단방향 빛 전파, 변형된 스넬의 법칙, 음굴절율, 투명 망토, 완전 흡수체와 같은 특이한 빛의 흐름을 지원하는, 이론적으로 증명된 인조 매질의 설계를 가능케 한다. 광 증폭 기술의 발전은 양자역학적 개념인 패리티-시간 대칭성의 구현에 적용되어, 복소 퍼텐셜에서의 새로운 종류의 광학을 탄생시켰다. 이러한 성취물들은 맥스웰 방정식에서의 더 넓고 급격한 형태의 대칭성 붕괴에 기반하기 때문에, 의도된 빛의 흐름 조절을 위해서는 다양한 대칭성 붕괴에 관한 심도있는 연구가 필요하다. 본 학위 논문에서는 복소, 불규칙, 비선형 광학 퍼텐셜과 같은 다양한 플랫폼에서의 대칭성 붕괴에 대하여 살펴보고자 한다. 본 연구는 패리티-시간 대칭성, 키랄 특성, 인과율, 초대칭, 생물 모방 기술, 모드 경계 광학 및 느린 빛 원리와 연계된 빛의 특이한 흐름에 집중한다. 본 연구진이 이끌어낸 비직관적인 개념 및 광소자의 새로운 설계 기법 관련 결과들은 비고전적인 빛의 흐름에 기반한 미래 광학 발전에 도움이 될 것이다.The flow of light in matters is usually defined by macroscopic Maxwells equations. In ideal media with homogeneous, isotropic, linear, and time-invariant optical material parameters, the aspect of light wave dynamics is simple and intuitive: propagating straight with oscillated electromagnetic fields, as the direct example of Fermats principle. This planewave dynamics, the basis of geometric optics, originates from the conservation of various symmetries of the Schrodinger-like wave equation, including translational and chiral symmetry, Hermitian symmetry, Lorentz reciprocity, and time-reversal symmetry. To control the flow of light even in a classical manner such as lens, mirror, and prism, some parts of the symmetries in optics should be broken. Breaking the translational symmetry with inhomogeneous materials is the traditional method of controlling light by scattering such as refraction, reflection, and diffraction. The dissipation or amplification of optical energy during the propagation is quantified by the non-Hermitian Hamiltonian of the wave equation. The materials composed of chiral molecules allow the rotation of the polarization of light, i.e. optical activity. The optical Doppler effect, which has been employed in astronomy for the observation of the motion of stars and galaxies, is based on the time-varying position of light sources, breaking Lorentz reciprocity. Recent achievements in optics, including counterintuitive theoretical results and improved fabrication technologies, have now been pioneering unprecedented regimes of controlling optical potentials which derive non-classical flow of light. Nano-scale technologies linked with the concept of metamaterials have opened a path to the design of theoretically-demonstrated artificial media supporting extraordinary light flows: such as unidirectional light flow, modified Snells law, negative index, cloaking, and perfect absorption. The development of optical amplification techniques has been applied to the realization of the quantum-mechanical notion of parity-time symmetry: stimulating a new class of optics in complex potentials. Because these achievements have been based on broader and drastic forms of symmetry breaking in Maxwells equations, in-depth investigation of various symmetry breakings is now imperative to realize designer manipulation of light flow. In this dissertation, we explore symmetry breakings in various platforms: complex, disordered, and nonlinear optical potentials. The investigation is focused on unconventional flows of light linked with the notions of parity-time symmetry, chirality, causality, supersymmetry, biomimetics, mode junction photonics, and slow-light. We believe that our results including counterintuitive concepts and novel design methods for optical devices will be the foundation of future development in optics based on non-classical flow of light.Table of Contents Abstract i Table of Contents iv List of Figures viii Chapter 1 Introduction １ 1.1 Why should we break the symmetry of light? １ 1.2 Outline of the dissertation ２ Chapter 2 Parity-Time Symmetric Optics ４ 2.1 Introduction to PT-symmetric optics ５ 2.2 PT-symmetric waves in the spatial domain １１ 2.2.1 2-level chirped system １１ 2.2.2 N-level photonic molecule ２４ 2.3 PT-symmetric waves in momentum domains ４３ 2.3.1 Optical chirality in low-dimensional eigensystems ４４ 2.3.2 Interpretation of PT-symmetry in k-space ６３ 2.4 Conclusion ７５ Chapter 3 Disordered Optics ７６ 3.1 Introduction to disordered optics ７７ 3.2 Supersymmetric bandgap in disorder ７８ 3.2.1 Wave dynamics in random-walk potentials ７９ 3.2.2 Supersymmetric transformation for isospectrality ８３ 3.2.3 Bloch-wave family with tunable disorder ８６ 3.3 Biomimetic disordered surface ９１ 3.4 Conclusion ９８ Chapter 4 All-Optical Devices with Nonlinearity ９９ 4.1 Introduction to all-optical devices １００ 4.2 Mode junction photonics １０１ 4.2.1 Photonic Junction Diode １０５ 4.2.2 Multi-Junction Half Adder １１３ 4.3 Slow-light enhanced optical functionalities １１５ 4.3.1 Multiband slow light １１６ 4.3.2 Optical A/D converter １２６ 4.3.3 All-optical A/D converter １３７ 4.3.4 Travelling-wave all-optical isolator １４３ 4.4 Conclusion １４９ Chapter 5 Conclusion １５０ Appendix A Eigenvalues in PT-Meta-molecules １５２ Appendix B Supplements for Section 2.3.1 １５７ B.1 Planewave solution of a PT-symmetric optical material １５７ B.2 Density of optical chirality for complex eigenmodes １５８ B.3 Effect of imperfect PT symmetry on the modal chirality １５９ B.3.1 Broken symmetry in the real part of permittivity １５９ B.3.2 Broken anti-symmetry in the imaginary part of the permittivity １６１ B.4 Transfer between RCP and LCP modes in the PT-symmetric chiral material １６２ B.4.1 Propagation of complex eigenmodes １６２ B.4.2 Strength of chiral conversion CCS before the EP １６３ B.5 The state of polarization (SOP) at the EP: Optical spin black hole １６４ B.6 Giant chiral conversion in the resonant structure １６５ B.7 Detailed information of fabrication and experiment in THz chiral polar metamaterials １６６ B.7.1 Fabrication process of THz chiral polar metamaterials １６６ B.7.2 THz-TDS system for the measurement of intermodal chirality １６７ B.8 Realization of PT-symmetric permittivity in metamaterial platforms １６７ B.9 Design parameters of chiral waveguides １７１ B.10 Low-dimensional linear polarization １７１ Appendix C Detailed Derivation for Section 2.3.2 １７３ C.1 Detailed derivation of Eq. (2.20) １７３ C.2 Serial calculation of discretized coupled mode equations １７５ Appendix D Analytical Methods for Section 3.2 １７７ D.1 Details of the FDM and FGH method １７７ D.2 Calculation of the Hurst exponent １７７ Appendix E Supplements for Section 4.2 １７９ E.1 Details of the device structures and numerical method used in the study １７９ E.2 Coupled mode theory for the di-atomic photonic junction diode １８１ E.2.1 Analytical model and coupled mode equations １８１ E.2.2. Solution of resonator field (a1, a2, a3) １８３ E.2.3 Implementation of Kerr nonlinearity and calculation of diode throughput １８５ Bibliography １８７ Abstract in Korean ２０３Docto