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Polarization dependent high refractive index metamaterial with metallic dielectric grating structure in infrared band

Li Jianmin, Chen Peng, Fang Bo, Cai Jinhui, Zhang Le, Wu Yinglai, Jing Xufeng

Optica Applicata

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2022

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Vol. 52, nr 3

441--460

EN

According to the theory of high refractive index of metamaterials, a composite structure of metal dielectric grating was designed to achieve high refractive index in infrared band. Based on the S-parameter inversion algorithm, we extracted the effective permittivity, the effective permeability, and the effective refractive index of the designed metamaterial. By changing the geometric parameters of the composite grating metamaterial structure, the effective refractive index of the designed metamaterial reaches more than 8.0 at the infrared resonance frequency. This is a high refractive index that many natural materials cannot achieve. It is noteworthy that the metamaterial structure has obvious polarization sensitivity. The metamaterial structure has both high refractive index and wideband zero refractive index properties when different polarized light is incident. At the same time, we further investigate the influence of metamaterial geometric parameters on the effective refractive index of metamaterials. Also, we propose a double grating metamaterial structure to obtain more degrees of freedom of metamaterial on the effective refractive index.

2

Broadband convolutional scattering characteristics of all dielectric transmission Pancharatnam–Berry geometric phase metasurfaces

Li Yiyun, Jin Yongxing, Jing Xufeng, Shi Lijiang, Li Chenxia, Hong Zhi

Optica Applicata

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2022

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Vol. 52, nr 2

297--323

EN

In order to obtain the broadband scattering characteristics, we propose a superperiodic cell structure with all-dielectric material to construct Pancharatnam–Berry geometric phase encoding metasurfaces. Because we cannot design or prepare infinitesimal coding unit particles, according to the generalized Snell’s law, we can only obtain discrete scattering angle regulation for the basic coding metasurface sequence. In order to obtain multi-angle scattering characteristics, we introduce the Fourier convolution principle in digital signal processing on the Pancharatnam–Berry geometric phase encoding metasurfaces. By using the addition and subtraction operations on two encoding metasurface sequences, a new encoding metasurface sequence can be obtained with different deflection angle. Fourier convolution operations on the encoding metasurfaces can provide an efficient method in optimizing encoding patterns to achieve continuous scattering beams. The addition and subtraction methods are also applicable to the checkerboard coding mode. The combination of Fourier convolution principle and Pancharatnam–Berry phase coded metasurface in digital signal processing can realize more powerful electromagnetic wave manipulation capability.

3

Enhancement of efficiency for broadband unidirectional light scattering by core-shell nanoantennas

Wang Weimin, Wang Xiaoyue, Huang Biqun, Jing Xufeng, Li Chenxia

Optica Applicata

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2019

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Vol. 49, nr 4

655--667

EN

A core-shell nanocube antenna is proposed to numerically simulate broadband unidirectional scattering. Comparing the scattering of a dielectric nanocube and core-shell nanocube, it is found that the core-shell nanocube has a higher forward/backward ratio and better unidirectional scattering efficiency. In order to further enhance forward scattering efficiency and reduce the side-lobe of scattering, the particle chain of core-shell nanocubes is proposed by arranging multiple nanoparticles. It is possible to achieve better unidirectional scattering over a wide spectral range. In addition, we also numerically studied the effect of the gap between the particles and the radius of the metal core on unidirectional scattering. It is demonstrated that the optimal gap should be selected to achieve ideal unidirectional forward scattering. The unique optical properties of core-shell nanocubes have important practical applications particularly in the fields of nanoantennas, photovoltaic devices, and nanolasers that require reflection suppression.