Abstract-Investigation of strong multimode interaction in a graphene-based hybrid coupled plasmonic system

Ye Ming Qing, Hui Feng Ma, Tie Jun Cui,

https://www.sciencedirect.com/science/article/pii/S0008622319300582


Multimode interaction in nanostructures plays a significant role for enhancing light-matter interactions. Here we investigate the hybrid electromagnetic couplings among graphene sheet plasmons (GSP) and magnetic polaritons (MP) in a coupled multimode system theoretically. The results both from the finite element method and coupled oscillator model reveal that the superposition of the resonance peaks generated by plasmonic hybridization can achieve multispectral perfect absorption. The electromagnetic energy at different resonance frequencies can be selectively localized at different positions of the nanostructure on purpose, exhibiting unique energy-transfer characteristics. The GSP mode can interact with MP modes by dynamically tuning the chemical potential of graphene, resulting in two distinct Rabi splitting phenomena with mode splitting energies of 10.34 meV and 16.54 meV, respectively. The strong coupling between GSP and MP can lead to the formation of multiple hybrid modes. Moreover, we further study the coupled four-mode system from both theoretical and simulation aspects, indicating that the general characteristics of mode interaction can be applied to more complicated multi-mode coupled systems. The presented results should be useful for multimode interaction studies, and have potential applications in highly tunable graphene-based plasmonic devices, such as thermal emitters, detectors, optical switches, multiband absorbers, etc.

Abstract-Tailoring anisotropic perfect absorption in monolayer black phosphorus by critical coupling at terahertz frequencies

Ye Ming Qing, Hui Feng Ma, and Tie Jun Cui

Fig. 1 (a) Schematic of the proposed structure. (b) Schematic of monolayer BP. (c) The single port resonator model in coupled mode theory. Frequency dependent surface conductivity along (d) the x-direction and (e) the y-direction. Solid lines and dashed lines denote the real part and imaginary part, respectively.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-25-32442

A metamaterial perfect absorber composed of a black phosphorus (BP) monolayer, a photonic crystal, and a metallic mirror is designed and investigated to enhance light absorption at terahertz frequencies. Numerical results reveal that the absorption is enhanced greatly with narrow spectra due to critical coupling, which is enabled by guided resonances. Intriguingly, the structure manifests the unusual polarization-dependent feature attributable to the anisotropy of black phosphorus. The quality factor of the absorber can be as high as 95.1 for one polarization while 63.5 for another polarization, which is consistent with the coupled wave theory. The absorption is tunable by varying key parameters, such as period, radius, slab thickness, incident angle, and polarization angle. Furthermore, the state of the system (i.e., critical coupling, over coupling, and under coupling) can be tuned by changing the electron doping of BP, thus achieving various applications. This work offers a paradigm to enhance the light-matter interaction in monolayer BP without plasmonic response, and this easy-to-fabricate structure will provide potential applications in BP-based devices.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Tailoring polarization and magnetization of absorbing terahertz metamaterials using a cut-wire sandwich structure

Hadi Teguh Yudistira, Shuo Liu,  Tie Jun Cui,  Han Zhang

a) Illustration of cut-wire sandwich structure. W, L, g, Zd and Zg are width of cut wire (20 µm), length of cut wire (100 µm), the gap size of cut wire with its neighbor (5 µm), polyimide substrate thickness (5 µm), and tge cut-wire structure thickness (100 nm), respectively. D is the lattice constant (D = L + g). b) Sample 1: cut-wire sandwich structure, c) Sample 2: cross-shaped sandwich structure, d) Sample 3: star-shaped sandwich structure.

https://www.beilstein-journals.org/bjnano/articles/9/136

The permittivity and permeability of a cut-wire sandwich structure can be controlled by laterally shifting the upper and lower layers. The use of this process for designing specific application-oriented devices may lack clear-cut guidelines because the lateral misalignment will significantly change the permittivity and permeability simultaneously. Therefore, in this work, we designed, fabricated and characterized a cut-wire sandwich device capable of tailoring the polarization and magnetization separately, thereby providing a promising recipe for achieving specific application objectives, such as a high-performance absorber. Accumulated charges effectively provided the polarization at the edge of cut-wires, and the surface current density on the cut-wires at top and bottom layers effectively generated the magnetization. By controlling and optimizing the geometrical configurations of the entire sandwich device (without lateral misalignment), the impedance could be matched to that of free space while generating a large imaginary part in the refractive index. This work characterizes the absorption performance of such sandwich structures in the terahertz regime. This mechanism could be further extended to other metamaterial devices in the terahertz and other frequency ranges because polarization and magnetization can now be selectively controlled in a straightforward manner.

Abstract-Revealing the physical mechanisms behind large field enhancement in hybrid spoof plasmonic systems

Yao Huang, Jingjing Zhang, Tie Jun Cui, Zhen Liao, and Dao Hua Zhang

https://www.osapublishing.org/josab/abstract.cfm?uri=josab-35-2-396&origin=search

We compare different spoof localized surface plasmon (LSP) schemes for increasing the field enhancement in the subwavelength regime. Based on the mechanisms of three differently widely used corrugated metallic disk structures, we compare three widely used corrugated disks and propose a nonconcentric spiral-shaped metallic disk structure, which not only maximizes the electromagnetic field confinement but also effectively reduces the radiation loss. The performance can be further improved by adopting a hybrid system consisting of two closely spaced nonconcentric spiral structures. We show that such a dimer of nonconcentric spiral disk produces significant field enhancement compared with the previously discussed structures. Our study provides a perceptive guideline for potential applications, such as plasmonic sensors and antennas, associated with LSPs in the microwave and terahertz frequencies.

© 2018 Optical Society of America

Abstract-Concepts, Working Principles, and Applications of Coding and Programmable Metamaterials

Shuo Liu,Tie Jun Cui,

http://onlinelibrary.wiley.com/doi/10.1002/adom.201700624/abstract

As a digital version of metamaterials, coding and programmable metamaterials have experienced rapid development since they were initially proposed in 2014. Unlike conventional metamaterials that are characterized by the sophisticated effective medium theory, coding metamaterials are described in a much simpler manner with binary codes, which builds up a bridge between the physical world and the digital world. In this article, the development of coding and programmable metamaterials in the past three years is reviewed, focusing primarily on the basic concept, working principle, design method, fabrication, and experimental validation. First, reflection-type and refraction-type coding metamaterials, along with two bifunctional coding metamaterials, are presented in the microwave, terahertz, and acoustic regimes. Second, the digital convolution theorem and information entropy of coding metamaterials are introduced to demonstrate the strong connection between metamaterials and information science. Then, recent progresses on engineering realization of field-programmable metamaterials are demonstrated, including the compensation technique of plane waves under point source illumination, and applications in single-sensor single-frequency imaging systems. Finally, future directions and potential applications are summarized, followed by discussions on major challenges encountered in the design and fabrication of programmable metamaterials at higher frequencies.

Abstract-Full-State Controls of Terahertz Waves Using Tensor Coding Metasurfaces

Shuo Liu, Hao Chi Zhang, Lei Zhang, Quan Long Yang, Quan Xu, Jian Qiang Gu, Yan Yang, XiaoYang Zhou, Jiaguang Han, Qiang Cheng, Weili Zhang, and Tie Jun Cui

ACS Appl. Mater. Interfaces, Just Accepted Manuscript

DOI: 10.1021/acsami.7b02789

Publication Date (Web): June 5, 2017

Copyright © 2017 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acsami.7b02789?journalCode=aamick

Coding metasurfaces allow us to study metamaterials from a fully-digital perspective, enabling many exotic functionalities such as anomalous reflections, broadband diffusions, and polarization conversion. Here, we propose a tensor coding metasurface at terahertz frequency that could take full-state controls of electromagnetic wave in terms of its polarization state, phase and amplitude distributions, and wave-vector mode. Due to the off-diagonal elements that dominant in the reflection matrix, each coding particle could reflects the normally incident wave to its cross polarization with controllable phases, resulting in different coding digits. A 3-bit tensor coding metasurface with three coding sequences is taken as example to show its full-state controls in reflecting normally incident terahertz beam to anomalous directions with cross polarizations, and making a spatially propagating wave (PW) to surface wave (SW) conversion at the terahertz frequency. We show that the proposed PW-SW convertor based on tensor coding metasurface supports both x and y-polarized normal incidences, producing cross-polarized transverse- magnetic (TM) and transverse-electric (TE) modes of terahertz SWs, respectively.

Abstract-Fast design of broadband terahertz diffusion metasurfaces

Jie Zhao, Qiang Cheng, Tian Qi Wang, Wei Yuan, and Tie Jun Cui

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-2-1050

A method for fast design of broadband terahertz diffusion metasurface is presented. The proposed metasurface is composed by three kinds of simply patterned elements with different resonant properties. To obtain the best broadband performance with the lowest backward reflections, a genetic algorithm is developed to manipulate the resonances for the fast determination of element geometries. An inverse discrete Fourier transform method is used to predict the scattering pattern of the metasurface with high accuracy and low time consumption, significantly enhancing the efficiency of the array-pattern design. The proposed fast design flow will benefit a broad range of terahertz applications, such as biological detection and imaging.

© 2017 Optical Society of America

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Abstract-Multi-beam reflections with flexible control of polarizations by using anisotropic metasurfaces

• Hui Feng Ma
• , Yan Qing Liu
• , Kang Luan
•  & Tie Jun Cui

http://www.nature.com/articles/srep39390

We propose a method to convert linearly polarized incident electromagnetic waves fed by a single source into multi-beam reflections with independent control of polarizations based on anisotropic metasurface at microwave frequencies. The metasurface is composed of Jerusalem Cross structures and grounded plane spaced by a dielectric substrate. By designing the reflection-phase distributions of the anisotropic metasurface along the x and y directions, the x- and y-polarized incident waves can be manipulated independently to realize multi-beam reflections. When the x- and y-polarized reflected beams are designed to the same direction with equal amplitude, the polarization state of the beam will be only controlled by the phase difference between the x- and y-polarized reflected waves. Three examples are presented to show the multi-beam reflections with flexible control of polarizations by using anisotropic metasurfaces and excellent performance. Particularly, we designed, fabricated, and measured an anisotropic metasurface for two reflected beams with one linearly polarized and the other circularly polarized. The measurement results have good agreement with the simulations in a broad bandwidth.

Abstract-Frequency-Dependent Dual-Functional Coding Metasurfaces at Terahertz Frequencies

http://onlinelibrary.wiley.com/doi/10.1002/adom.201600471/full

A frequency-dependent dual-functional coding metasurface is proposed at terahertz frequencies using two layers of metamaterial structures, each of which is responsible for the independent control of reflection phases at two distinct frequencies. The zero interference between the functionalities at the lower and higher frequencies are promising for possible applications in multicolor holography for color displays or a frequency beam splitter.