Phase modulation of metasurfaces for polarization conversion and RCS reduction

In this study, the phase modulation ability of a dielectric Pancharatnam–Berry (PB) phase metasurface, consisting of nanofins, is theoretically analyzed. It is generally considered that the optical thickness of the unit cell of a PB-phase metasurface is λ/2, i.e., a half-waveplate for polarization conversion. It is found that the λ/2 is not essential for achieving a full 2π modulation. Nevertheless, a λ/2 thickness is still needed for a high polarization conversion efficiency. Moreover, a gradient phase metasurface is designed. With the help of the particle swarm optimization (PSO) method, the wavefront errors of the gradient phase metasurface are reduced by fine-tuning the rotation angle of the nanofins. The diffraction efficiency of the gradient phase metasurface is thus improved from 73.4% to 87.3%. This design rule can be utilized to optimize the efficiency of phase-type meta-devices, such as meta-deflectors and metalenses.

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Polarization conversion and phase modulation of terahertz electromagnetic waves via graphene-dielectric structure

Physica Scripta ◽

10.1088/1402-4896/ab461d ◽

2019 ◽

Vol 95 (1) ◽

pp. 015503

Author(s):

M Karimi Habil ◽

S Roshan Entezar

Keyword(s):

Phase Modulation ◽

Electromagnetic Waves ◽

Polarization Conversion ◽

Dielectric Structure

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Vanadium dioxide-assisted switchable broadband terahertz metasurface for polarization conversion and phase modulation

Journal of Optics ◽

10.1088/2040-8986/ac2ddb ◽

2021 ◽

Author(s):

Yun Li ◽

Heng Zhang ◽

Tongtong Li ◽

Bin Zhang

Keyword(s):

Vanadium Dioxide ◽

Phase Modulation ◽

Polarization Conversion ◽

Broadband Terahertz

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Full 360∘ Terahertz Dynamic Phase Modulation Based on Doubly Resonant Graphene-Metal Hybrid Metasurfaces

10.20944/preprints202110.0430.v1 ◽

2021 ◽

Author(s):

Binxu Wang ◽

Xiaoqing Luo ◽

Yalin Lu ◽

Guangyuan Li

Keyword(s):

Fermi Energy ◽

Phase Modulation ◽

Beam Steering ◽

Polarization Conversion ◽

Terahertz Waves ◽

Dynamic Phase ◽

Phase Profile ◽

Profile Design ◽

Simulation Results ◽

High Reflectance

Dynamic phase modulation is vital for tunable focusing, beaming, polarization conversion and holography. However, it remains challenging to achieve full 360∘ dynamic phase modulation while maintaining high reflectance or transmittance based on metamaterials or metasurfaces in the terahertz regime. Here we propose a doubly resonant graphene-metal hybrid metasurface to address this challenge. Simulation results show that by varying the graphene Fermi energy, the proposed metasurface with two shifting resonances is capable to provide dynamic phase modulation covering a range of 361∘ while maintaining relatively high reflectance above 20% at 1.05 THz. Based on the phase profile design, dynamically tunable beam steering and focusing are numerically demonstrated. We expect this work will advance the engineering of graphene metasurfaces for the dynamic manipulation of terahertz waves.

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The observation of solutions in Ni3Nb

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104765 ◽

1988 ◽

Vol 46 ◽

pp. 540-541

Author(s):

Z.M. Wang ◽

J.P. Zhang

Keyword(s):

Electron Microscopy ◽

High Resolution ◽

Phase Modulation ◽

High Resolution Electron Microscopy ◽

Antiphase Domain ◽

Boundary Area ◽

Matrix Type ◽

Resolution Electron ◽

Domain Boundaries ◽

Kontorova Model

High resolution electron microscopy reveals that antiphase domain boundaries in β-Ni3Nb have a hexagonal unit cell with lattice parameters ah=aβ and ch=bβ, where aβ and bβ are of the orthogonal β matrix. (See Figure 1.) Some of these boundaries can creep “upstairs” leaving an incoherent area, as shown in region P. When the stepped boundaries meet each other, they do not lose their own character. Our consideration in this work is to estimate the influnce of the natural misfit δ{(ab-aβ)/aβ≠0}. Defining the displacement field at the boundary as a phase modulation Φ(x), following the Frenkel-Kontorova model [2], we consider the boundary area to be made up of a two unit chain, the upper portion of which can move and the lower portion of the β matrix type, assumed to be fixed. (See the schematic pattern in Figure 2(a)).

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