Abstract-Electrically tunable superconducting terahertz metamaterial with low insertion loss and high switchable ratios

Chun Li1, Caihong Zhang1,a), Guoliang Hu1, Gaochao Zhou1, Shoulu Jiang1, Chengtao Jiang1, Guanghao Zhu1, Biaobing Jin1,b), Lin Kang1,Weiwei Xu1, Jian Chen1 and Peiheng Wu1


1 Research Institute of Superconductor Electronics (RISE), School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
a) Electronic mail: chzhang@nju.edu.cn
b) Electronic mail: bbjin@nju.edu.cn
Appl. Phys. Lett. 109, 022601 (2016); http://dx.doi.org/10.1063/1.4955454

http://scitation.aip.org/content/aip/journal/apl/109/2/10.1063/1.4955454

With the emergence and development of artificially structured electromagnetic materials, active terahertz (THz) metamaterial devices have attracted significant attention in recent years. Tunability of transmission is desirable for many applications. For example, short-range wireless THz communications and ultrafast THz interconnects require switches and modulators. However, the tunable range of transmission amplitude of existing THz metamaterial devices is not satisfactory. In this article, we experimentally demonstrate an electrically tunable superconducting niobium nitride metamaterial device and employ a hybrid coupling model to analyze its optical transmission characteristics. The maximum transmission coefficient at 0.507 THz is 0.98 and decreases to 0.19 when the applied voltage increases to 0.9 V. A relative transmittance change of 80.6% is observed, making this device an efficient narrowband THz switch. Additionally, the frequency of the peak is red shifted from 0.507 to 0.425 THz, which means that the device can be used to select the frequency. This study offers an alternative tuning method to existing optical, thermal, magnetic-field, and electric-field tuning, delivering a promising approach for designing active and miniaturized THz devices.

Abstract-Anomalous Terahertz Reflection and Scattering by Flexible and Conformal Coding Metamaterials

1. Lanju Liang¹, 
2. Meiqing Qi², 
3. Jing Yang³,
4. Xiaopeng Shen², 
5. Jiquan Zhai¹, 
6. Weizong Xu⁴, 
7. Biaobing Jin^1,5,*, 
8. Weiwei Liu^3,5,*,
9. Yijun Feng⁴, 
10. Caihong Zhang¹, 
11. Hai Lu⁴,
12. Hou-Tong Chen⁶, 
13. Lin Kang¹, 
14. Weiwei Xu¹,
15. Jian Chen^1,5, 
16. Tie Jun Cui^2,5,*, 
17. Peiheng Wu¹ and
18. Shenggang Liu^5,7

Article first published online: 30 JUN 2015

http://onlinelibrary.wiley.com/doi/10.1002/adom.201500206/abstract;jsessionid=75D9087BA4464D14DC4C0EA2F158CD85.f03t01?userIsAuthenticated=false&deniedAccessCustomisedMessage=

DOI: 10.1002/adom.201500206

© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Arbitrary control of terahertz (THz) waves remains a significant challenge although it promises many important applications. Here, a method to tailor the reflection and scattering of THz waves in an anomalous manner by using 1-bit coding metamaterials is presented. Specific coding sequences result in various THz far-field reflection and scattering patterns, ranging from a single beam to two, three, and numerous beams, which depart obviously from the ordinary Snell's law of reflection. By optimizing the coding sequences, a wideband THz thin film metamaterial with extremely low specular reflection, due to the scattering of the incident wave into various directions, is demonstrated. As a result, the reflection from a flat and flexible metamaterial can be nearly uniformly distributed in the half space with small intensity at each specific direction, manifesting a diffuse reflection from a rough surface. Both simulation and experimental results show that a reflectivity less than −10 dB is achieved over a wide frequency range from 0.8 to 1.4 THz, and it is insensitive to the polarization of the incident wave. This work reveals new opportunities arising from coding metamaterials in effective manipulation of THz wave propagation and may offer widespread applications.

Abstract-Nonlinear terahertz superconducting plasmonics

Jingbo Wu¹, Caihong Zhang², Lanju Liang¹, Biaobing Jin^1,a), Iwao Kawayama²,Hironaru Murakami², Lin Kang¹, Weiwei Xu¹, Huabing Wang^1,3, Jian Chen¹,Masayoshi Tonouchi^2,a) and Peiheng Wu^1,a)
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a) Electronic addresses: bbjin@nju.edu.cn; tonouchi@ile.osaka-u.ac.jp; and phwu@nju.edu.cn
Appl. Phys. Lett. 105, 162602 (2014); http://dx.doi.org/10.1063/1.4898818

http://scitation.aip.org/content/aip/journal/apl/105/16/10.1063/1.4898818

Nonlinear terahertz (THz) transmission through subwavelength hole array in superconductingniobium nitride (NbN) film is experimentally investigated using intense THz pulses. The good agreement between the measurement and numerical simulations indicates that the field strength dependent transmission mainly arises from the nonlinear properties of thesuperconducting film. Under weak THz pulses, the transmission peak can be tuned over a frequency range of 145 GHz which is attributed to the high kinetic inductance of 50 nm-thick NbN film. Utilizing the THz pump-THz probe spectroscopy, we study the dynamic process of transmission spectra and demonstrate that the transition time of such superconducting plasmonic device is within 5 ps.