High-Speed Efficient Terahertz Modulation Based on Tunable Collective-Individual State Conversion within an Active 3 nm Two-Dimensional Electron Gas Metasurface

• Published in: Nano letters 2019-11, Vol.19 (11), p.7588-7597
• Main Authors: Zhao, Yuncheng, Wang, Lan, Zhang, Yaxin, Qiao, Shen, Liang, Shixiong, Zhou, Tianchi, Zhang, Xilin, Guo, Xiaoqing, Feng, Zhihong, Lan, Feng, Chen, Zhi, Yang, Xiaobo, Yang, Ziqiang
• Format: Article
• Language: English
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.9b01273

Terahertz (THz) modulators are always realized by dynamically manipulating the conversion between different resonant modes within a single unit cell of an active metasurface. In this Letter, to achieve real high-speed THz modulation, we present a staggered netlike two-dimensional electron gas (2DEG) nanostructure composite metasurface that has two states: a collective state with massive surface resonant characteristics and an individual state with meta-atom resonant characteristics. By controlling the electron transport of the nanoscale 2DEG with an electrical grid, collective-individual state conversion can be realized in this composite metasurface. Unlike traditional resonant mode conversion confined in meta-units, this state conversion enables the resonant modes to be flexibly distributed throughout the metasurface, leading to a frequency shift of nearly 99% in both the simulated and experimental transmission spectra. Moreover, such a mechanism can effectively suppress parasitic modes and significantly reduce the capacitance of the metasurface. Thereby, this composite metasurface can efficiently control the transmission characteristics of THz waves with high-speed modulations. As a result, 93% modulation depth is observed in the static experiment and modulated sinusoidal signals up to 3 GHz are achieved in the dynamic experiment, while the −3 dB bandwidth can reach up to 1 GHz. This tunable collective-individual state conversion may have great application potential in wireless communication and coded imaging.