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Principles Of Optics Electromagnetic Theory Of Propagation Interference And Diffraction Of Light

Tables of integrals

Metamaterials are composed of periodic subwavelength metal/dielectric structures that resonantly couple to the electric and/or magnetic components of the incident electromagnetic fields, exhibiting properties that are not found in nature. This class of micro- and nano-structured artificial media have attracted great interest during the past 15 years and yielded ground-breaking electromagnetic and photonic phenomena. However, the high losses and strong dispersion associated with the resonant responses and the use of metallic structures, as well as the difficulty in fabricating the micro- and nanoscale 3D structures, have hindered practical applications of metamaterials. Planar metamaterials with subwavelength thickness, or metasurfaces, consisting of single-layer or few-layer stacks of planar structures, can be readily fabricated using lithography and nanoprinting methods, and the ultrathin thickness in the wave propagation direction can greatly suppress the undesirable losses. Metasurfaces enable a spatially varying optical response (e.g. scattering amplitude, phase, and polarization), mold optical wavefronts into shapes that can be designed at will, and facilitate the integration of functional materials to accomplish active control and greatly enhanced nonlinear response. This paper reviews recent progress in the physics of metasurfaces operating at wavelengths ranging from microwave to visible. We provide an overview of key metasurface concepts such as anomalous reflection and refraction, and introduce metasurfaces based on the Pancharatnam-Berry phase and Huygens' metasurfaces, as well as their use in wavefront shaping and beam forming applications, followed by a discussion of polarization conversion in few-layer metasurfaces and their related properties. An overview of dielectric metasurfaces reveals their ability to realize unique functionalities coupled with Mie resonances and their low ohmic losses. We also describe metasurfaces for wave guidance and radiation control, as well as active and nonlinear metasurfaces. Finally, we conclude by providing our opinions of opportunities and challenges in this rapidly developing research field.

A review of metasurfaces: physics and applications.

The advent of negative index materials has spawned extensive research into metamaterials over the past decade. Metamaterials are attractive not only for their exotic electromagnetic properties, but also their promise for applications. A particular branch–the metamaterial perfect absorber (MPA)–has garnered interest due to the fact that it can achieve unity absorptivity of electromagnetic waves. Since its first experimental demonstration in 2008, the MPA has progressed significantly with designs shown across the electromagnetic spectrum, from microwave to optical. In this Progress Report we give an overview of the field and discuss a selection of examples and related applications. The ability of the MPA to exhibit extreme performance flexibility will be discussed and the theory underlying their operation and limitations will be established. Insight is given into what we can expect from this rapidly expanding field and future challenges will be addressed.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/adma.201200674

Metamaterial Electromagnetic Wave Absorbers

Metamaterials are composed of periodic subwavelength metal/dielectric structures that resonantly couple to the electric and/or magnetic components of the incident electromagnetic fields, exhibiting properties that are not found in nature. Planar metamaterials with subwavelength thickness, or metasurfaces, consisting of single-layer or few-layer stacks of planar structures, can be readily fabricated using lithography and nanoprinting methods, and the ultrathin thickness in the wave propagation direction can greatly suppress the undesirable losses. Metasurfaces enable a spatially varying optical response, mold optical wavefronts into shapes that can be designed at will, and facilitate the integration of functional materials to accomplish active control and greatly enhanced nonlinear response. This paper reviews recent progress in the physics of metasurfaces operating at wavelengths ranging from microwave to visible. We provide an overview of key metasurface concepts such as anomalous reflection and refraction, and introduce metasurfaces based on the Pancharatnam-Berry phase and Huygens' metasurfaces, as well as their use in wavefront shaping and beam forming applications, followed by a discussion of polarization conversion in few-layer metasurfaces and their related properties. An overview of dielectric metasurfaces reveals their ability to realize unique functionalities coupled with Mie resonances and their low ohmic losses. We also describe metasurfaces for wave guidance and radiation control, as well as active and nonlinear metasurfaces. Finally, we conclude by providing our opinions of opportunities and challenges in this rapidly developing research field.

A review of metasurfaces: physics and applications

A broadband two-dimensional Luneburg lens is presented based on gradient index metamaterials. The focusing condition of the lens, requiring a gradient refractive index, is achieved by using the electromagnetic resonators. A novel modified split ring resonator is chosen as the unit cell since its permeability and permittivity can keep constants when the operating band is far away from the resonant frequency. A standard retrieval procedure is used to determine the relationship between the geometry of the unit cells and the refraction index. Therefore, a new kind of Luneburg lens composed of the modified SRR arrays is constructed. Simulation results have shown that the proposed Luneburg lens, which operating in X-band, has an excellent focusing ability.

Broadband two-dimensional planar luneburg lens composed of gradient index metamaterials

In this paper, the lightning-generated electromagnetic fields over lossy ground produced by lightning strikes either to flat ground or to rugged terrain are calculated using the 2-D finite-difference time-domain (FDTD) method. In order to find the changing trend of vertical electric fields induced by lightning strike with different height and gradient of rugged terrain, we set the height to 40m, 60m, 80m, 100m and 120m and the width of top to 20m, 40m, 60m, 80m and 100m, respectively. We find the vertical electric field Ez at the top of rugged terrain enhanced and the vertical electric field near the upland reduced. Further more, with increasing height of upland, the vertical electric field rises on the top and falls near the rugged terrain. With increasing gradient of slope, the vertical electric decreases around the upland.

Analysis of lightning-induced electromagnetic fields near rugged terrain in cylindrical coordinates

In this paper, a new co-design approach for a band-stop filtering tunable phase shifter based on liquid crystal (LC) is proposed and developed for the first time, which can provide tunable phase shift and self-embedded stable filtering function at the same time. The equivalent lumped circuit model and the transmission parameter are both given to illustrate the stable stop band caused by different sizes of hairpin resonators in detail. The simulation results show that the proposed filtering tunable phase shifter not only realizes the stable stop band from 4.9 GHz to 6.0 GHz, but also indicates that the FoM is more than 100°/dB in the pass band, which provide a good verification for the theoretical concepts.

Analysis and Co-Design of Band-Stop Filter and Tunable Liquid Crystal Phase Shifter

A novel multi-band frequency selective surfaces (FSS) based on fractal triangle elements is proposed. The structure consists of three regular triangles placed into a larger one and many nesting triangles of different lengths and apex angles inside in front of a dielectric slab. Simulation by CST MICROWAVE STUDIO® is conducted to analyze the characteristics of the structure. The results show that the FSS has three resonant frequencies in frequency band 0–20GHz, good angle stability and polarization stability. Moreover, effects of the parameters of the structure: the length of the side, the apex angle and the nesting number are analyzed, which provides theoretical basis for practical use.

Research on a novel multi-band fractal triangle frequency selective surfaces

200 elements uniformly spaced, symmetrically weighted, x-axis linear array with principal plane in azimuth was thinned using the Cross Entropy to achieve a sidelobe power of less than −20 dB. And convergence properties for best and mean scores of population over 5000 trials were performed, then simulation results to synthesis were compared with the GA. It was first work utilizing the Cross Entropy method for solving electromagnetic optimization problems.

Qun Wu

Papers

Broadband two-dimensional planar luneburg lens composed of gradient index metamaterials

Analysis of lightning-induced electromagnetic fields near rugged terrain in cylindrical coordinates

Analysis and Co-Design of Band-Stop Filter and Tunable Liquid Crystal Phase Shifter

Research on a novel multi-band fractal triangle frequency selective surfaces

Aperiodic array synthesis using the Cross Entropy method