Abstract-Accessing the High-Q Dark Plasmonic Fano Resonances in Superconductor Metasurfaces

http://onlinelibrary.wiley.com/doi/10.1002/adom.201600354/abstract

Superconducting metamaterials at terahertz frequencies has provided a platform for designing switchable plasmonic metamaterial devices. However, since metals at terahertz frequencies are excellent conductors, the superior role of superconductors in designing low-loss, high quality factor metamaterials remains unclear. In this work, a low asymmetry Fano resonant split-ring-resonator is considered in which a regime of extremely low radiative loss is identified where the high temperature yttrium barium copper oxide superconductor meta-atom supports a sharp high quality factor Fano resonance while an identical metallic resonator does not show the resonance behavior. The radiative and the nonradiative losses are comparable in low asymmetry Fano resonant meta-atoms. The observation of high quality factor Fano resonance behavior clearly establishes the utility of superconductors over metals in designing lower loss plasmonic metamaterials at terahertz frequencies that may have multifunctional applications in areas that require strong light–matter interactions.

Abstract-Giant nonlinearity in a superconducting sub-terahertz metamaterial

V. Savinov1,a), K. Delfanazari1, V. A. Fedotov1 and N. I. Zheludev1,2

1 Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Southampton, SO17 1BJ, United Kingdom

2 Centre for Disruptive Photonic Technologies, TPI, Nanyang Technological University, Singapore 637371, Singapore

a) vs1106@orc.soton.ac.uk

Appl. Phys. Lett. 108, 101107 (2016);

 http://dx.doi.org/10.1063/1.4943649

We report a superconducting sub-THz metamaterial operating in a CW-regime, which exhibits a record-breaking resonant third-order nonlinearity with effective n2∼10 cm2/W$n_2\sim 10\hspace{0.17em}{\text{cm}}^2/\mathrm{W}$. The nonlinear response is caused by the radiation-induced resistive heating, suppressing the superconductivity in the nano-scale constrictions of the structure's meta-molecules. The nonlinearity has a relaxation time of 25 μs$25\hspace{0.17em}\mu \mathrm{s}$ and leads to a substantial change of the amplitude and phase of the transmitted radiation at intensities of only 500 μW/cm2$500\hspace{0.17em}\mu {\mathrm{W}/\text{cm}}^2$.

Abstract-Terahertz Saturable Absorption in Superconducting Metamaterials

George R. Keiser, Jingdi Zhang, Xiaoguang Zhao, Xin Zhang, Richard D. Averitt
https://export.arxiv.org/abs/1601.02496


We present a superconducting metamaterial saturable absorber at terahertz frequencies. The absorber consists of an array of split ring resonators (SRRs) etched from a 100nm YBaCu3O7 (YBCO) film. A polyimide spacer layer and gold ground plane are deposited above the SRRs, creating a reflecting perfect absorber. Increasing either the temperature or incident electric field (E) decreases the superconducting condensate density and corresponding kinetic inductance of the SRRs. This alters the impedance matching in the metamaterial, reducing the peak absorption. At low electric fields, the absorption was optimized near 80% at T=10K and decreased to 20% at T=70K. For E=40kV/cm and T=10K, the peak absorption was 70% decreasing to 40% at 200kV/cm, corresponding to a modulation of 43%.

Abstract-Terahertz superconducting metamaterials for magnetic tunability

Dongyang Wang1, Zhen Tian1, Caihong Zhang2, Xiaoqing Jia2, Biaobing Jin2, Jianqiang Gu1, Jiaguang Han1 and Weili Zhang1,3

http://iopscience.iop.org/2040-8986/16/9/094013

jiaghan@tju.edu.cn weili.zhang@okstate.edu

1 Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Tianjin University, and the Key Laboratory of Optoelectronics Information and Technology, Tianjin 300072, People's Republic of China
2 Research Institute of Superconductor Electronics (RISE), School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, People's Republic of China
3 School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, USA 

We present the magnetic tunability of a metamaterial made from superconducting niobium nitride film. The inductive-capacitive resonance excited by a normally incident terahertz wave was found to be continuously modulated through an external magnetic field at temperatures below the superconducting transition point. A giant resonance modulation was observed due to a strong magnetic effect, where the variation of the magnetic field alters the intrinsic conductivity of the superconducting film. The high sensitivity of the metamaterial allows us to observe the temperature-dependent magnetic effect, and the magnitude of resonance modulation decreases with increasing temperatures. This work demonstrates that a strong magnetic effect could be implemented as an active control modality in superconducting integrated devices functioning at terahertz frequencies