phase gradient
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Author(s):  
Wenyuan Zhang ◽  
Haojun Xu ◽  
Binbin Pei ◽  
Xiaolong Wei ◽  
Pei Feng ◽  
...  

Abstract This work proposes a new plasma super-phase gradient metasurfaces (PS-PGMs) structure, owing to the limitations of the thin-layer plasma for electromagnetic wave attenuation. Based on the cross-shaped surface unit configuration, we have designed the X-band absorbing structure through the dispersion control method. By setting up the Drude dispersion model in the computer simulation technology, the designed phase gradient metasurfaces structure is superposed over the plasma, and the PS-PGMs structure is constructed. The electromagnetic scattering characteristics of the new structure have been simulated, and the reflectance measurement has been carried out to verify the absorbing effect. The results demonstrate that the attenuation effect of the new structure is superior to that of the pure plasma structure, which invokes an improved attenuation effect from the thin layer plasma, thus enhancing the feasibility of applying the plasma stealth technology to the local stealth of the strong scattering part of a combat aircraft.


Nanomaterials ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 113
Author(s):  
Quan He ◽  
Zhe Shen

The beam splitter is a common and critical element in optical systems. Traditional beam splitters composed of prisms or wave plates are difficult to be applied to miniaturized optical systems because they are bulky and heavy. The realization of the nanoscale beam splitter with a flexible function has attracted much attention from researchers. Here, we proposed a polarization-insensitive beam splitter with a variable split angle and ratio based on the phase gradient metasurface, which is composed of two types of nanorod arrays with opposite phase gradients. Different split angles are achieved by changing the magnitude of the phase gradient based on the principle of Snell’s law of refraction, and different split ratios are achieved by adding a phase buffer with different areas. In the designed four types of beam splitters for different functions, the split angle is variable in the range of 12–29°, and the split ratio is variable in the range of 0.1–1. The beam splitter has a high beam splitting efficiency above 0.3 at the wavelength of 480–600 nm and a weak polarization dependence. The proposed beam splitter has the advantages of a small size and easy integration, and it can be applied to various optical systems such as multiplexers and interferometers for integrated optical circuits.


Author(s):  
Yong-Qiang Liu ◽  
Zhongru Ren ◽  
Yingchao Shu ◽  
Lujun Wu ◽  
Jinhai Sun ◽  
...  

Abstract Broadband metalenses consist of sub-wavelength phase gradient elements are indispensable in modern science and technology. So far, several broadband optical metalenses are demonstrated but mostly with either small NA or relatively low focusing efficiency. Herein, an ultra-thin broadband microwave metalens (frequency range from 8.0GHz to 10.5GHz) with both high-efficiency above 40% and large NA more than 0.6 is presented. The metalens is also fabricated and the measurement results agree with the simulations very well. The performances of the presented broadband metalens can surpass nowadays microwave metalens largely and open up new vistas for low-profile, low-cost and light-weight microwave components.


Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7348
Author(s):  
Radosław Żurowski ◽  
Justyna Zygmuntowicz ◽  
Paulina Piotrkiewicz ◽  
Marcin Wachowski ◽  
Michał M. Szczypiński

This paper focuses on the verifying the possibility of producing Al2O3-ZrO2 composite pipes with a gradient structure using centrifugal slip casting method. The aim of the research is to define the correlation between the rheological properties of aqueous suspensions of ceramic powders with different solid loading and obtaining the ZrO2 phase gradient in the Al2O3 matrix. Such products, due to their unique properties, can be utilized in the transport of aggressive substances, even in extreme temperature or corrosive conditions. The suspensions and the sintered samples were characterized by: broad rheological analysis, scanning electron microscopy, X-ray diffraction, stereological analysis and Vickers hardness tests. The study reports on a series of samples produced of ceramic suspensions (70 vol.% Al2O3–30 vol.% ZrO2) differing in the total solid loading in the range of 30–55 vol.%. The results clearly indicate that obtaining the gradient structure of ceramic-ceramic composite pipes is closely related to the rheological properties of the suspensions from which the samples are cast. The phase gradient is obtainable from suspensions 30–40 vol.%, in which the possibility of moving ZrO2 particles relative to the Al2O3 is quite high—these suspensions are characterized by low viscosity and the dominance of viscous over elastic properties (G′ > G″).


2021 ◽  
Author(s):  
Khushboo Singh ◽  
Muhammad U. Afzal ◽  
Karu P. Esselle

Abstract Near-field Meta-Steering (NFMS) is a constantly evolving and progressively emerging novel antenna beam-steering technology that involves an elegant assembly of a base antenna and a pair of phase-gradient metasurfaces (PGMs) placed in the near-field region of the antenna aperture. The upper PGM in a Near-Field Meta-Steering system receives an oblique incidence from the lower PGM at all times, a fact that is ignored in the traditional design process of upper metasurfaces. This work proposes an accurate optimization method for metasurfaces in NFMS systems to reduce signal leakage by suppressing the grating lobes and side lobes that are innate artifacts of beam-steering. We detail the design and optimization approach for both upper and lower metasurface. Compared to the conventionally optimized compact 2D steering system, the proposed system exhibits higher directivity and lower sidelobe and grating lobe levels within the entire scanning range. The broadside directivity is 1.4 dB higher, and the sidelobe level is 4dB lower in comparison. The beam-steering patterns for the proposed 2D compact design are experimentally validated, and the measured and predicted results are in excellent concurrence. The versatile compatibility of truncated PGMs with a low gain antenna makes it a compelling technology for wireless backhaul mesh networks and future antenna hardware.


2021 ◽  
pp. 1-31
Author(s):  
Arnab Pattanayak ◽  
Avik Hati ◽  
Siddhartha P. Duttagupta

2021 ◽  
Author(s):  
Khushboo Singh ◽  
Muhammad U. Afzal ◽  
Ali Lalbakhsh ◽  
Karu P. Esselle

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Siyuan Shen ◽  
Zhaohui Ruan ◽  
Yuan Yuan ◽  
Heping Tan

Abstract The generalized Snell’s law dictates that introducing a phase gradient at the interface of two media can shape incident light and achieve anomalous reflection or refraction. However, when the introduced phase gradient is realized via the scattering of nanoparticles in the metasurfaces, this law needs to be modified; certain conditions need to be met when the law is established. We present the conditions for establishing the “generalized Snell’s law of refraction” in all-dielectric metasurfaces under the incidence of different polarized light. These conditions can provide theoretical bases for the subsequent design of high-efficiency beam deflection metasurfaces. The relationship between the highest achievable anomalous refraction efficiency and the number of nanoparticles within one period of the metasurface is also summarized. In addition, the generalized refraction should not depend on the polarization states of incident light; however, the previous realization conditions of anomalous refraction were sensitive to the polarization states. Thus, conditions for establishing the polarization-independent generalized Snell’s law of refraction in all-dielectric metasurfaces are presented.


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