Abstract-Tunable terahertz hybrid graphene-metal patterns metamaterials

Chenyuyi Shi, Xiaoyong He, Jun Peng, Guina Xiao, Feng Liu, Fangting Lin, Hao Zhang,



https://www.sciencedirect.com/science/article/pii/S0030399218317250

Based on the hybrid metal-graphene structures, we investigated the tunable Fano resonances in the terahertz region, including the effects of graphene Fermi levels, structural parameters, and operation frequencies. The results reveal that an obvious Fano resonance can be observed, the maximum peak value of Fano resonance can reach 0.9711, and its Q-quality factor is more about 20. With the help of the graphene layer, the resonant curves of the proposed structures can be effectively modulated, the frequency modulation depth can reach 60% as the Fermi level changes in the range of 0.1–1.0 eV. In addition, by varying the length of graphene bar in the scope of 10–60 μm, the amplitude modulation depths are about 21.0%. The results are helpful for designing novel graphene-based tunable terahertz devices with high Q factor, e.g. modulators, sensors and antenna.

Abstract-Graphene patterns supported terahertz tunable plasmon induced transparency

Xiaoyong He, Feng Liu, Fangting Lin, and Wangzhou Shi

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-8-9931

The tunable plasmonic induced transparency has been theoretically investigated based on graphene patterns/SiO2/Si/polymer multilayer structure in the terahertz regime, including the effects of graphene Fermi level, structural parameters and operation frequency. The results manifest that obvious Fano peak can be observed and efficiently modulated because of the strong coupling between incident light and graphene pattern structures. As Fermi level increases, the peak amplitude of Fano resonance increases, and the resonant peak position shifts to high frequency. The amplitude modulation depth of Fano curves is about 40% on condition that the Fermi level changes in the scope of 0.2-1.0 eV. With the distance between cut wire and double semi-circular patterns increases, the peak amplitude and figure of merit increases. The results are very helpful to develop novel graphene plasmonic devices (e.g.sensors, modulators, and antenna) and find potential applications in the fields of biomedical sensing and wireless communications.

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

Abstract-Investigation of graphene-supported tunable asymmetric terahertz metamaterials

Chenyuyi Shi, Xiaoyong He, Feng Liu, Fangting Lin, and Hao Zhang

https://www.osapublishing.org/josab/abstract.cfm?uri=josab-35-3-575

By integrating a graphene layer with asymmetric split-ring metamaterial (MM) metal resonators, we investigated tunable propagation properties in the terahertz regime, including the effects of graphene Fermi levels, structural parameters, and operation frequencies. The results reveal that a sharp inductor-capacitor (LC) resonance can be observed at low frequency for the asymmetric MM structure, and its 𝑄$Q$ factor can reach more than 17.5. With the help of a graphene layer, the optical response is modulated efficiently. For instance, if the Fermi level changes in the range of 0.01–0.3 eV, for the semiconductor MM structure, the modulation depths (MDs) of amplitude and frequency are 27.0% and 43.4%, respectively. In addition, the resonant curves of indium antimonide (InSb) MMs can be modulated by changing the temperature; the amplitude MD is 56.2% as the temperature changes in the range of 350–800 K. The 𝑄$Q$ factor of the InSb MM structure is about 44.6. The results are helpful for designing novel graphene-based tunable terahertz devices, e.g., filters and modulators.

© 2018 Optical Society of America

Abstract-Switchable metamaterial for enhancing and localizing electromagnetic field at terahertz band

Junxing Liu, Kailin Zhang, Xiankuan Liu, Zeyu Zhang, Zuanming Jin, Xiaoyong He, and Guohong Ma

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-13-13944

In this article, a novel metamaterial is designed aimed at generating a single electromagnetic hot spot, in order to realize the localization of the incident electromagnetic field at terahertz band, and this kind of metastructure is an ideal candidate for many research fields such as spintronics, nonlinear magnetic response, near-field optics, and optical antenna, etc. The specially tailored metamaterial takes the shape of diabolo with a metal triangle pair connected by a cubic gallium arsenide (GaAs) gap. We demonstrated by simulation that both electric- and magnetic-field of incident THz pulse can be confined in the small GaAs gap when a synchronized femtosecond laser pulse is illuminated. The numerical simulation results show that 2 orders of magnitude of field enhancement can be obtained for a 1-by-1 μm GaAs gap, and the field enhancement factor can also be further improved by tailoring the GaAs gap down to nanometer scale.

© 2017 Optical Society of America

Abstract-Investigation of graphene assisted tunable terahertz metamaterials absorber

Xiaoyong He, Xu Zhong, Fangting Lin, and Wangzhou Shi
http://proxy.osapublishing.org/ome/abstract.cfm?uri=ome-6-2-331

By using the graphene-SiO2-Si-dielectrics-metallic ground plane (GSiO2SiDM) structures, we investigate the tunable properties of graphene metamaterials (MMs) absorbers in the terahertz region, including the effects of operation frequency, Fermi level, and graphene structure patterns. The results manifest that the graphene tunable GSiO2SiDM structure can achieve net absorption by changing structure parameters and the Fermi level of graphene layer. The resonant absorption and reflection curves of the GSiO2SiDM structures can be shifted in a wide range via controlling the applied electric fields. The modulation depth of resonant amplitude and frequency can reach more than 60% and 30%, respectively. The resonant peak (dip) of the absorption (reflection) curves shift to high frequency with the increase of Fermi level of the graphene layer. Due to broad absorption curve, the graphene MMs absorbers structures are suitable for the fabrication of broad absorber. The results are very useful to design novel devices, such as thermal detectors, imager, and biosensors.

© 2016 Optical Society of America

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Abstract-Theoretical investigation of semiconductor supported tunable terahertz dielectric loaded surface plasmons waveguides

• Chunlin Liu, 
• Xiaoyong He, 
• Zhenyu Zhao, 
• Hao Zhang, 
• Wangzhou Shi

• Department of Physics, Mathematics & Science College, Shanghai Normal University, No. 100 Guilin Road, Shanghai 200234, PR China

Received 16 April 2015, Revised 12 July 2015, Accepted 21 July 2015, Available online 30 July 2015

http://www.sciencedirect.com/science/article/pii/S0030401815006604

The tunable propagation properties of semiconductor-based dielectric loaded surface plasmons (DLSPs) structures have been theoretically investigated in the THz regime, including the effects of temperature, operation frequency, and the thermo-optic effect of dielectric stripe materials. The results show that the waveguide properties of DLSPs structure can be modulated in a wide range via changing the temperature. For instance, when the temperature is changed in the range of 300–600 K, the modulation depth of propagation length can reach more than 80%. With the increase of refractive index of the dielectric stripe, the modulation depth of the effective indices and propagation lengths increase. In addition, the propagation length and figure of the merit can be improved obviously with the hybrid dielectric stripe structure (by coating Si on the SiO₂ layer). The results are very helpful to design novel waveguide devices, such as modulators, switchers, sensors and polarizers.

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.

Abstract-Graphene-supported tunable extraordinary transmission

Xiaoyong He1 and Hongxia Lu2

xyhethz@hotmail.com

1 Mathematics & Science College, Shanghai Normal University, No. 100 Guilin Rd., Shanghai, 200234, People's Republic of China
2 School of Material Science and Engineering, Zhengzhou University, No. 100 Science Rd., Zhengzhou, Henan, 450001, People's Republic of China 

http://iopscience.iop.org/0957-4484/25/32/325201

By depositing a graphene layer on the metallic film with subwavelength hole arrays, the tunable extraordinary transmission property based on the metal-dielectrics-graphene (MDG) structure has been investigated in the terahertz (THz) and near-infrared (NIR) regimes. The influences of operation frequency, composed materials, and the Fermi level of the graphene layer have been taken into account. The results show that by varying the Fermi level of the graphene layer, the transmission of the MDG structure can be tuned in a wide range and the modulation depth of the peak value of the transmission can reach more than 50%. But the tunable mechanisms in the THz and NIR regimes are quite different. In the infrared (THz) regime, the graphene behaves like the dielectric (metallic) layer; its dielectric constant decreases (increases) with the increase of Fermi level, resulting in the transmission increasing (decreasing). Compared with the metallic structure, the transmission of the semiconductor structure can also be modulated by using the doping or varying temperature; its peak position can also be changed in a much broader range. The results are very useful to understand the mechanism of the graphene plasmonic devices and to design novel filters, switchers, modulators, and sensors.