Abstract-Design of a size-efficient tunable metamaterial absorber based on leaf-shaped cell at near-infrared regions

Hailong Huang, Hu Xia, Wenke Xie,  Zhibo Guo, Hongjian Li,

https://www.sciencedirect.com/science/article/pii/S2211379718305692

A size-efficient tunable metamaterial absorber (MA) composed of metallic leaf-shaped cell, graphene layer, silicon substrate, and bottom metal film is investigated theoretically and numerically at near-infrared (NIR) regions. Simulation results reveal that the single-band high absorption of 91.9% is obtained at 1268.7 nm. Further results show that the single-band can be simply changed into dual-band high absorption by varying the geometric parameters of top metallic layer at same wavelength regions, yielding two high absorption coefficients of 96.6% and 95.3% at the wavelengths of 1158.7 nm and 1323.6 nm, respectively. And the effect of related geometric parameter on dual-band absorption intensities is also investigated to obtain the optimized one. The peak wavelength can be tuned via modifying the Fermi energy of the graphene layer through controlling the external gate voltage. The work shows that the proposed strategy can be applied to other design of the dual-band structure at infrared regions.

Abstract-Novel tunable terahertz graphene metamaterial with an ultrahigh group index over a broad bandwidth

Hui Xu, Hongjian Li, Zhiquan Chen, Mingfei Zheng, Mingzhuo Zhao, Cuixiu Xiong and Baihui Zhang

http://iopscience.iop.org/article/10.7567/APEX.11.042003/meta

We propose a grating-coupled graphene metamaterial structure at a terahertz band. An obvious tunable plasmon-induced transparency can be achieved by changing the graphene Fermi level, and there is a very high absorption peak in the spectrum. Thus, this structure can be used to realize a terahertz modulator or absorption device with two outstanding functions. Using phase changes, we have also studied the slow light effect, and we find that there is a broad ultrahigh-group-index band, and the maximum group index can reach 216. This research may open up new avenues for slow light devices.

Abstract-Theoretical Analysis of Plasmon-Induced Transparency in Ring-resonators Coupled Channel Drop Filter Systems

• Shiping Zhan, 
• Hongjian Li, 
• Guangtao Cao, 
• Zhihui He, 
• Boxun Li, 
• Hui Xu

http://link.springer.com/article/10.1007/s11468-014-9760-x

The plasmon-induced transparency (PIT) in ring-resonators coupled channel drop filter (CDF) systems is investigated theoretically and numerically in this paper. A coupled mode theory-based transfer matrix method (CMT-TMM) is introduced owning to the symmetric and evanescent coupling, which is confirmed by the finite-difference time-domain (FDTD) simulation results. The drop waveguide provides the necessary optical feedback for the interference effect in realizing the PIT, and a new way for adjusting PIT effect in a fixed structure is also given. Finally, the phase and the group dispersion in the transparency window are discussed for investigating the slow light effect in our systems, and a group index of ~22 is obtained. The proposed plasmonic systems possess both the slow light and the dropping properties and may have potential and flexible applications in fundamental research of integrated plasmonic devices.