Abstract-Dynamically controllable terahertz absorber based on a graphene-vanadium dioxide-metal configuration

 

Jingyu Zhang, Xiaoqing Yang, Xiaojing Huang, Fuyu Li, Peng Liu. Kechang Fu

https://www.sciencedirect.com/science/article/abs/pii/S0749603621000070

Metamaterials have attracted much attention due to their subwavelength scales, especially in the field of designing terahertz devices. In this paper, a graphene-vanadium oxide (VO2) composite aluminum (GVCA) metamaterial absorber with two-dimensional control properties is designed. The simulation results show that the number of narrowband absorption peaks in the absorption spectrum can be switched through the phase transition characteristics of VO2. The number of narrow-band absorption peaks before and after the phase transition is one and two, and the absorption efficiency is 100% and 90%, respectively. The physical mechanism of narrowband absorption peaks is analyzed by electric field and surface current distribution. The influencing factors of narrowband absorption peaks are explored, including the line length of graphene, the linewidth of graphene and the side length of VO2. Through active regulation of the graphene Fermi level, the absorption bandwidth can completely cover the entire frequency bawnd of 0.1 to 1.1 THz, and the absorption efficiency can be maintained at about 90%. For different linear polarized (LP) waves, the influence of the incident angle on the absorption performance is studied respectively. This work promotes the application of metamaterials in THz imaging, sensing, and cloaking.

Abstract-The terahertz metamaterials for sensitive biosensors in the detection of ethanol solutions

Author links open overlay panelFuyu Li, Ke He, Tingting Tang, Yinghui Mao, Rui Wang, Chaoyang Li, Jian Shen,

                                               

https://www.sciencedirect.com/science/article/abs/pii/S0030401820307045 

Metamaterials have attracted much attention due to their subwavelength characteristics, especially in the field of unlabeled refractive index sensing. Because biomolecular molecules have special biological fingerprint spectra in terahertz band, high sensitivity sensor components can be realized by using the special electromagnetic response of metamaterials. In this paper, a novel biosensor based on electromagnetic induced reflection is designed. We find that the asymmetrically fractured double-ring resonator can effectively enhance the fano-resonance of electromagnetic induction reflection, where the resonance position occurs at 1.57 THz. Oscillating Lorentz model shows that when the resonant detuning continues to increase, the bright mode and the dark mode are strongly coupled. When the light mode decreases, the radiation loss also decreases, which induces the decrease of resonance ability. The sensitivity of pure ethanol solution (analyte) under  coating thickness is 103.7 GHz/RIU, 107.1 GHz/RIU and 112.05 GHz/RIU, respectively. The sensitivity and full width at half maximum (FWHM) of the sensor are studied from the perspectives of analyte concentration, thickness, and proportion, respectively. The results show the great potential of electromagnetic metamaterials as sensitive sensors in biological solution detection.

Abstract-All-optical switchable terahertz spin-photonic devices based on vanadium dioxide integrated metasurfaces

Jie Li, Jitao Li, Yating Zhang, Jining Li, Yue Yang, Hongliang Zhao, Chenglong Zheng, Jiahui Li, Jin Huang, Fuyu Li, Tingting Tang, Jianquan Yao,



https://www.sciencedirect.com/science/article/abs/pii/S0030401819310545

Metasurfaces based on Pancharatnam-Berry (P-B) phase can achieve strong spin angular momentum (SAM) to orbital angular momentum (OAM) conversion of light, which provides a new degree of freedom for light control and opens up a new way for the applications of metasurfaces in classical and quantum optics. With the development of high-speed, large-capacity information transmission and high-definition imaging, demand for multifunctional and tunable P-B phase metasurfaces increases. Here, we propose three switchable terahertz spin-photonic devices based on P-B phase metasurfaces for focusing (divergence), splitting and vortex generation of terahertz beams. Based on photo-induced insulator–metal phase transition of the vanadium dioxide (VO2) islands in reflective hybrid resonators, switching of the devices function between on- and off-state is obtained, and the amplitude switching efficiency is as high as 90%. This work provides new ideas for the design of active terahertz devices and facilitates the applications of terahertz spin-photonic devices based on metasurfaces.