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-Asymmetric transmission of linearly polarized waves in terahertz chiral metamaterials

Shenying Fang1,a), Kang Luan2,a), Hui Feng Ma2, Wenjin Lv1, Yuxiang Li1,b), Zheng Zhu1, Chunying Guan1, Jinhui Shi1,3,b), and Tie Jun Cui

http://aip.scitation.org/doi/abs/10.1063/1.4974477

We experimentally demonstrate the asymmetric transmission of linearly polarized waves in a multilayer chiral metamaterial in the terahertz (THz) regime. The chiral metamaterial is constructed by two stacked orthogonal metallic layers embedded in polyimide dielectric layers. Simulated and measured results show that the proposed multilayer chiral metamaterial can achieve dual-band direction-dependent cross-polarization conversions for both x- and y-polarized THz waves. The polarized wave passing through the metamaterial will be converted into its orthogonal polarization state, while the same polarized wave is blocked along the reversed propagation direction. In addition, the asymmetric transmission band may be effectively engineered to other frequencies by slightly adjusting the gap width. We believe that our findings are beneficial in manipulating the polarization state of THz waves and exploring polarization-sensitive THz devices.

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-Anisotropic coding metamaterials and their powerful manipulation of differently polarized terahertz waves

Shuo Liu^1,2,*, Tie Jun Cui^1,3,*, Quan Xu⁴, Di Bao^1,2, Liangliang Du⁴, Xiang Wan^1,2, Wen Xuan Tang^1,2, Chunmei Ouyang⁴, Xiao Yang Zhou^1,2,5, Hao Yuan⁵, Hui Feng Ma^1,2, Wei Xiang Jiang^1,2, Jiaguang Han⁴, Weili Zhang^3,4 and Qiang Cheng^1,3

1. ¹State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210096, China
2. ²Synergetic Innovation Center of Wireless Communication Technology, Southeast University, Nanjing 210096, China
3. ³Cooperative Innovation Centre of Terahertz Science, Chengdu 610054, China
4. ⁴Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China
5. ⁵Jiangsu Xuantu Technology Co., Ltd., Nanjing 211111, China

Correspondence: TJ Cui, Email: tjcui@seu.edu.cn

^*These authors contributed equally to this work.

Received 29 September 2015; Revised 19 January 2016; Accepted 20 January 2016
Accepted article preview online 26 January 2016

http://www.nature.com/lsa/journal/v5/n5/full/lsa201676a.html

Metamaterials based on effective media can be used to produce a number of unusual physical properties (for example, negative refraction and invisibility cloaking) because they can be tailored with effective medium parameters that do not occur in nature. Recently, the use of coding metamaterials has been suggested for the control of electromagnetic waves through the design of coding sequences using digital elements ‘0’ and ‘1,' which possess opposite phase responses. Here we propose the concept of an anisotropic coding metamaterial in which the coding behaviors in different directions are dependent on the polarization status of the electromagnetic waves. We experimentally demonstrate an ultrathin and flexible polarization-controlled anisotropic coding metasurface that functions in the terahertz regime using specially designed coding elements. By encoding the elements with elaborately designed coding sequences (both 1-bit and 2-bit sequences), the x- and y-polarized waves can be anomalously reflected or independently diffused in three dimensions. The simulated far-field scattering patterns and near-field distributions are presented to illustrate the dual-functional performance of the encoded metasurface, and the results are consistent with the measured results. We further demonstrate the ability of the anisotropic coding metasurfaces to generate a beam splitter and realize simultaneous anomalous reflections and polarization conversions, thus providing powerful control of differently polarized electromagnetic waves. The proposed method enables versatile beam behaviors under orthogonal polarizations using a single metasurface and has the potential for use in the development of interesting terahertz devices.