Abstract-Plasmon-induced transparency-like behavior at terahertz region via dipole oscillation detuning in a hybrid planar metamaterial

Plasmon-induced transparency-like behavior at terahertz region via dipole oscillation detuning in a hybrid planar metamaterial

Zhenyu Zhao, Zhiqiang Song, Wangzhou Shi, and Wei Peng

https://www.osapublishing.org/ome/abstract.cfm?uri=ome-6-7-2190

We investigate a plasmon-induced transparency (PIT)-like behavior at terahertz (THz) region induced by resonance detuning in a hybrid planar metamaterial (MM). Each unit cell of the MM contains two types of dipole oscillation resonators: a cut-wire and a couple of U-shaped resonators in mirror symmetry. The hybridization of above resonators splits the single resonance mode into two side modes in THz transmission spectrum. The side modes are found to induce negative group delays of incident THz wave-packet. The distribution of surface currents and electric energy reveals that the near-field coupling between cut-wire and U-shape resonators results in inductive-capacitive (LC) resonance, which dominates the low frequency side mode, while the high frequency side mode attribute to the triple dipole oscillations. The reduction of the length of cut-wire give rise to a dipole resonance detuning, which enhances the LC resonance via near-field coupling, while attenuates the constructive inference of triple dipole oscillators. The retrieved complex dielectric functions indicate the evolution of LC resonance and triple dipole oscillations. By controlling the dipole resonance detuning appropriately, a man-made transparent tip can be created in between the two side modes. However, such a transparent tip is unable to induce negative group delay. Aforementioned PIT-like behavior can support the design of hybrid planar MMs in application of two-band notch filters or multi-channel buffer in the THz-region.

© 2016 Optical Society of America

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Abstract-Terahertz response of fractal meta-atoms based on concentric rectangular square resonators

Zhiqiang Song^1,a), Zhenyu Zhao^1,a),b), Wei Peng² and Wangzhou Shi¹
 HIDE AFFILIATIONS
1 Department of Physics, Shanghai Normal University, Shanghai 200234, China
2 State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
a) Z. Song and Z. Zhao contributed equally to this work.
b) Electronic mail: zyzhao@shnu.edu.cn
J. Appl. Phys. 118, 193103 (2015); http://dx.doi.org/10.1063/1.4936217

http://scitation.aip.org/content/aip/journal/jap/118/19/10.1063/1.4936217?TRACK=RSS

We investigate the terahertz electromagnetic responses of fractal meta-atoms (MAs) induced by different mode coupling mechanisms. Two types of MAs based on concentric rectangular square (CRS) resonators are presented: independent CRS (I-CRS) and junctional-CRS (J-CRS). In I-CRS, each resonator works as an independent dipole so as to result in the multiple resonance modes when the fractal level is above 1. In J-CRS, however, the generated layer is rotated by π/2 radius to the adjacent CRS in one MA. The multiple resonance modes are coupled into a single mode resonance. The fractal level increasing induces resonance modesredshift in I-CRS while blueshift in J-CRS. When the fractal level is below 4, the mode Q factor of J-CRS is in between the two modes of I-CRS; when the fractal level is 4 or above, the mode Q factor of J-CRS exceeds the two modes of I-CRS. Furthermore, the modulation depth (MD) decreases in I-CRS while it increases in J-CRS with the increase in fractal levels. The surfacecurrents analysis reveals that the capacitive coupling of modes in I-CRS results in the modesredshift, while the conductive coupling of modes in J-CRS induces the mode blueshift. A high Q mode with large MD can be achieved via conductive coupling between the resonators of different scales in a fractal MA.

Abstract-Teeter-totter effect of terahertz dual modes in C-shaped complementary split-ring resonators

Zhiqiang Song¹, Zhenyu Zhao^1,a), Hongwei Zhao², Wei Peng³, Xiaoyong He¹ and Wangzhou Shi¹
http://scitation.aip.org/content/aip/journal/jap/118/4/10.1063/1.4927845
1 Department of Physics, Shanghai Normal University, Shanghai 200234, China
2 Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, China
3 State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
a) Electronic mail: zyzhao@shnu.edu.cn
J. Appl. Phys. 118, 043108 (2015); http://dx.doi.org/10.1063/1.4927845

A teeter-totter effect of terahertz (THz) resonant modes in C-shaped complementary split-ringresonators (CSRRs) is observed. The dual resonant mode transmission enhancement was investigated using THz time-domain spectroscopy. The intensity of the lower-frequency resonance modes increases monotonically with the CSSR gap width, which is accompanied by a monotonic decrease in the intensity of the higher-frequency resonance modes. The origin of the dual resonant modes is numerically explained by the electromagnetic energy density distribution and surface current analysis. The inductive-capacitive resonance dominates the lower frequency mode, while the dipole oscillation dominates the higher frequency mode. By tuning the gap of the CSRR, an equilibrant transmittance of above dual resonance modes can be designed. This teeter-totter effect promises a possible application of CSSRs as potential dual-bandpass filters in the THz-region.