Abstract-All-dielectric metamaterial analogue of electromagnetically induced transparency and its sensing application in terahertz range

Tian Ma, Qiuping Huang, Hongchuan He, Yi Zhao, XIaoxia Lin, and Yalin Lu

Fig. 2 (a) Schematic of the all-dielectric metamaterial composed of two asymmetric split ring resonators. Inset: top view of the unit cell. All dimensions shown here are $h=100\mu m,$ $t=30\mu m,$ $P_x=400\mu m,$ $P_y=400\mu m,$ $R_1=75\mu m,$ $R_2=75\mu m,$ $\alpha =160°,$ and $\beta =120°.$ (b) Microscopy of the fabricated sample. Bars refer to 500μm. (c) Transmission spectra and (d) corresponding group delay of the proposed metamaterial

http://aoip.osa.org/oe/abstract.cfm?uri=oe-27-12-16624

A novel electromagnetically induced transparency (EIT) all-dielectric metamaterial is proposed, fabricated, and characterized. The unit cell of the proposed metamaterial comprises of two asymmetric split ring resonators (a-SRRs) positioned with a mirror symmetry. The asymmetric nature of a-SRRs results from the length difference of two arcs. Optical properties of the fabricated metamaterial are investigated numerically using finite difference method, as well as experimentally using a terahertz time-domain spectroscopy. The results confirm that the proposed metamaterial exhibits an EIT transparent window in the frequency range around 0.78THz with a Q-factor of ~75.7 and a time-delay up to ~28.9ps. Theoretical investigations show that EIT effects in our metamaterial are achieved by hybridizing two bright modes in the same unit cell, which are aroused by the excitation of magnetic moments. We also confirm that the proposed metamaterial has great potential for sensing applications with high sensitivity and high figure of merit (FOM), which guarantees potential applications in in situ chemical and biological sensing.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-A broadband and switchable VO2-based perfect absorber at the THz frequency

Yi Zhao, Qiuping Huang, Honglei Cai, Xiaoxia Lin, Yalin Lu,



https://www.sciencedirect.com/science/article/abs/pii/S0030401818304772

We demonstrate a broadband and switchable THz metamaterial absorber by utilizing the phase transition of VO2, which is a stacked structure composed of VO2 periodic array, dielectric layer, VO${}_2$ film, Au periodic array, dielectric layer and Au reflective layer, respectively. The absorption band from 0.76 THz to 0.86 THz at room temperature can be changed into the absorption band from 1.12 THz to 1.25 THz when temperature increases above the phase change temperature of VO2, with the absorptivity in both bands over 90%. Furthermore, the effective medium theory is introduced to explain the perfect absorption mechanism. Such absorber can work well over a wide range of incidence around 40°. Thickness of the absorber is only about one twentieth of the working wavelength. The proposed structure can be applied to absorbers working at other frequencies.

Abstract-Multifunctional Hybrid Metasurfaces for Dynamic Tuning of Terahertz Waves

Honglei Cai,  Shi Chen,   Chongwen Zou,   Qiuping Huang,   Yu Liu,  Xiang Hu,   Zhengping Fu,  Yi Zhao,  Hongchuan He,   Yalin Lu,

https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201800257


Actively tuning optical transmission through hybrid metasurfaces incorporated with multifunctional active media holds great promise for the next generation optical devices. In the terahertz (THz) range, they remain rare due to the lack of dynamic and multifunctional designs and materials. Here, a vanadium dioxide (VO2)‐based hybrid metasurface is proposed to present multifunctional control of THz waves via electrically triggering and ultrafast optical excitation. By minimizing the thermal mass of VO2 and optimizing the VO2 patterns within two side gaps of the asymmetric split‐ring resonators, a hybrid metasurface which can tune the THz wave with an absolute modulation depth up to 54% and a figure of merit as high as 138% is hereby presented. The hybrid metasurface achieves a switching time of 2.2 s under the electrically triggering and offers an ultrafast modulation within 30 ps under the femtosecond pulse excitation. More interestingly, owing to the intrinsic hysteresis behavior of VO2, the hybrid metasurface exhibits distinguishing multistate transmission amplitudes with a single electrical input. In short, this study paves the way for robust multifunctionality in electric‐controlled terahertz switching, photonic memory, and ultrafast terahertz optics.

Abstract- Broadband diffusion metasurface based on a single anisotropic element and optimized by the Simulated Annealing algorithm

• Yi Zhao
• , Xiangyu Cao
• , Jun Gao
• , Yu Sun
• , Huanhuan Yang
• , Xiao Liu
• , Yulong Zhou
• , Tong Han
•  & Wei Chen

• http://www.nature.com/articles/srep23896

We propose a new strategy to design broadband and wide angle diffusion metasurfaces. An anisotropic structure which has opposite phases under x- and y-polarized incidence is employed as the “0” and “1” elements base on the concept of coding metamaterial. To obtain a uniform backward scattering under normal incidence, Simulated Annealing algorithm is utilized in this paper to calculate the optimal layout. The proposed method provides an efficient way to design diffusion metasurface with a simple structure, which has been proved by both simulations and measurements.