Abstract-A Review of THz Modulators with Dynamic Tunable Metasurfaces

Lan Wang,  Yaxin Zhang , Xiaoqing Guo, Ting Chen, Huajie Liang,  Xiaolin Hao,  Xu Hou, Wei Kou,  Yuncheng Zhao,  Tianchi Zhou,  Shixiong Liang, Ziqiang Yang

https://www.mdpi.com/2079-4991/9/7/965/htm

Terahertz (THz) radiation has received much attention during the past few decades for its potential applications in various fields, such as spectroscopy, imaging, and wireless communications. To use terahertz waves for data transmission in different application systems, the efficient and rapid modulation of terahertz waves is required and has become an in-depth research topic. Since the turn of the century, research on metasurfaces has rapidly developed, and the scope of novel functions and operating frequency ranges has been substantially expanded, especially in the terahertz range. The combination of metasurfaces and semiconductors has facilitated both new opportunities for the development of dynamic THz functional devices and significant achievements in THz modulators. This paper provides an overview of THz modulators based on different kinds of dynamic tunable metasurfaces combined with semiconductors, two-dimensional electron gas heterostructures, superconductors, phase-transition materials, graphene, and other 2D material. Based on the overview, a brief discussion with perspectives will be presented. We hope that this review will help more researchers learn about the recent developments and challenges of THz modulators and contribute to this field.

Abstract-Dynamic Photoinduced Controlling of the Large Phase Shift of Terahertz Waves via Vanadium Dioxide Coupling Nanostructures

Yuncheng Zhao, Yaxin Zhang, Qiwu Shi, Shixiong Liang,  Wanxia Huang,  Wei Kou,  Ziqiang Yang,

https://pubs.acs.org/doi/10.1021/acsphotonics.8b00276

Utilizing terahertz (THz) waves to transmit data for communication and imaging places high demands on phase modulation. However, until now, it is difficult to realize a more than 100° phase shift in the transmission mode with one-layer structure. In this paper, a ring-dumbbell composite resonator nested with VO2 nanostructures is proposed to achieve the large phase shift. It is found that in this structure a hybrid mode with an enhanced resonant intensity, which is coupled by the L-C resonance and dipole resonance has been observed. Applying the photoinduced phase transition characteristics of VO2, the resonant intensity of the mode can be dynamically controlled, which leads to a large phase shift in the incident THz wave. The dynamic experimental results show that controlling the power of the external laser can achieve a phase shift of up to 138° near 0.6 THz using this one-layer VO2 nested composite structure. Moreover, within a 55 GHz (575–630 GHz) bandwidth, the phase shift exceeds 130°. This attractive phase shift modulation may provide prospective applications in THz imaging, communications, and so on.

Abstract-Linear polarization conversion of transmitted terahertz wave with double-layer meta-grating surfaces

Han Sun, Yaxin Zhang, Kailong Wang, Yuncheng Zhao, Wei Kou, Shixiong Liang, Jiaguang Han, and Ziqiang Yang

https://www.osapublishing.org/col/abstract.cfm?uri=col-16-8-081601

In this Letter, we demonstrate a linear polarization conversion of transmitted terahertz wave with double-layer meta-grating surfaces, which integrated the frequency selectivity of a split ring resonator metasurface and the polarization selectivity of a metallic grating surface. Since the double-layer can reduce the loss, and the Fabry–Perot like resonant effect between the two layers can improve the conversion efficiency, this converter can rotate the incident y-polarized terahertz wave into an x-polarized transmitted wave with relatively low loss and high efficiency. Experimental results show that an average conversion efficiency exceeding 75% from 0.25 to 0.65 THz with the highest efficiency of 90% at 0.43 THz with only −2  dB loss has been achieved.

© 2018 Chinese Laser Press

Abstract-Dynamic Photo-induced Controlling of the Large Phase Shift of Terahertz Waves via Vanadium Dioxide Coupling Nanostructures

Yuncheng Zhao, Yaxin Zhang, Qiwu Shi, Shixiong Liang, Wanxia Huang, Wei Kou, Ziqiang Yang,

https://pubs.acs.org/doi/abs/10.1021/acsphotonics.8b00276?mi=aayia761&af=R&AllField=nano&target=default&targetTab=std

Utilizing terahertz (THz) waves to transmit data for communication and imaging places high demands on phase modulation. However, until now, realizing a large phase shift using a one-layer structure in transmission mode has been difficult. In this paper, utilizing a composite unit cell by coupling the traditional metallic wire dipolar resonance and the split-ring capacitive inductance resonance results in an enhanced resonance coupling mode. Combined with a vanadium dioxide (VO2) nanostructure and applying the photo-induced phase transition, the resonant intensity of the mode can be dynamically controlled, which leads to an ultralarge phase shift in the incident THz wave. The dynamic experimental results show that controlling the power of the external laser can achieve a phase shift of up to 138 degrees near 0.6 THz using this one-layer VO2 nested composite structure. Moreover, within a 55 GHz (575 GHz-630 GHz) bandwidth, the phase shift exceeds 130 degrees. This attractive phase shift modulation may provide prospective applications in THz imaging, communications, etc.