Yuncheng Zhao, Lan Wang, Yaxin Zhang, Shen Qiao, Shixiong Liang, Xilin Zhang, Xiaoqing Guo, Zhihong Feng, Feng Lan, Zhi Chen, Xiaobo Yang, Ziqiang Yang,
https://pubs.acs.org/doi/abs/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 paper, 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 -3dB bandwidth can reach up to 1GHz. This tunable collective-individual state conversion may have great application potential in wireless communication and coded imaging.
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