Zhong-Hao Sa

Bio: Zhong-Hao Sa is an academic researcher from Nanjing University. The author has contributed to research in topics: Metamaterial & Transformation optics. The author has an hindex of 1, co-authored 1 publications receiving 1 citations.

Invisible Gateway by Superscattering Effect of Metamaterials.

Abstract: Illusion devices, such as superscatterer and invisible gateway, have been theoretically studied under the theory of transformation optics and folded geometry transformations. The realization of these devices needs building blocks of metamaterials with negative permittivities and permeabilities. However, superscattering effects, such as stopping wave propagation in an air channel, have not been verified from illusion devices physically because of the challenge of metamaterial design, fabrication, and material loss. In this Letter, we implement a big metamaterial superscatterer, and experimentally demonstrate its superscattering effect at microwave frequencies by field-mapping technology. We confirm that superscattering is originated from the excitation of surface plasmons. Integrated with superscatterer, we experimentally display that an invisible gateway could stop electromagnetic waves in an air channel with a width much larger than the cutoff width of the corresponding rectangular waveguide. Our results provide a first direct observation of superscattering effect of double negative metamaterials and invisible gateway for electromagnetic waves. It builds up an ideal platform for future designs of other illusion devices.

Ceramic‐based dielectric metamaterials

Abstract: Dielectric metamaterials based on ceramics have attracted considerable interest in the past few years owing to their low dielectric loss, simple structure, excellent multifield tunability, and good environmental adaptability. They are considered to be promising alternative to metal‐based metamaterials and can lead to a new strategy for the development of passive devices. In this review, the recent progress of ceramic‐based dielectric metamaterials in electromagnetic applications, energy applications, non‐Hermitian systems, and natural materials with near‐zero or negative refraction are summarized. The design principle and mechanism, as well as manufacturing technologies, are also introduced, and the current development trend of ceramic‐based dielectric metamaterials are proposed.

Broadband Polarization Manipulation Based on W-Shaped Metasurface

Abstract: We present a metasurface consisting of W-shaped resonators to realize broadband reflective linear and circular polarization conversions. We find that the cross polarization conversion ratio for normal incidence is over 0.95 from 9.2 to 18.7 GHz, covering 68.1% of the central frequency. We also show that, the conversion performance is almost insensitive to the angle of incident waves. Furthermore, by simply adjusting the geometrical parameters of the W-shaped metasurface, the broadband circular polarization conversion is also achieved. We emphasize that the bandwidth of axis ratio less than 3.0 dB covers from 10.1 to 17.7 GHz, equivalent to 54.7% relative bandwidth. Due to these broadband and high-efficiency polarization conversion features, our proposal may have a wide application prospect.

Acoustic superscatterer enables remote mitigation of underwater source radiation

Abstract: We propose a contactless and non-closed strategy to mitigate the sound radiated from an underwater source. The problem is formulated as the interaction of the source with different cross-sectional shapes (including ideal zero-cross-section sources, circular-cross-section rods, and rectangular-cross-section rods) and the acoustic superscatterer treated as a concentric cylindrical structure. The acoustic superscatterer consisting of an internal core and a coating made of the double-negative acoustic metamaterial with specific constitutive parameters relies on the coating to virtually magnify its internal core, thus yielding intense multiple scattering with the source. According to the transformation media theory and the method of images, the complete landscape has been presented theoretically and numerically of the remote mitigation of underwater source radiation via an acoustic superscatterer. We demonstrate that by appropriately placing the acoustic superscatterer nearby the source, it can achieve the omnidirectional radiation mitigation stemming from the coherent extinction mechanism. A possible scheme for the practical realization of the acoustic superscatterer is also discussed. This work may facilitate the design and application of remotely placed meta-devices for the manipulation of underwater acoustic waves.

Transmission Enhancement through Sub-Wavelength Aperture Based on Regulable Water-Based Metamaterial

Abstract: A realization form of the Mie resonance with adjustable characteristics based on a water-based metamaterial is proposed. A novel local electromagnetic field coupling mechanism based on a water-based metamaterial is established, which is used for transmission enhancement through the sub-wavelength aperture for the first time. The water-based metamaterial particle for transmission enhancement at a specific frequency is designed. By designing the microfluidic control system to control the water filling (i.e., height) of the metamaterial particle, the adjustable transmission enhancement characteristics are realized. The influence of bilateral symmetry and flexible deformation of the metamaterial particle on the transmission characteristics is analyzed. The influence of the design parameters on the enhanced transmission characteristics is discussed.