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
School of Electronic Science and Engineering , University of Electronic Science and Technology of China , Chengdu 610054 , China.
National Key Laboratory of Application Specific Integrated Circuit , Hebei Semiconductor Research Institute , Shijiazhuang 050051 , China.
Nano Lett. 2019 Nov 13;19(11):7588-7597. doi: 10.1021/acs.nanolett.9b01273. Epub 2019 Aug 22.
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.
太赫兹（THz）调制器通常通过动态操纵有源超表面单个单元胞内不同谐振模式之间的转换来实现。在本信函中，为了实现真正的高速太赫兹调制，我们提出了一种交错网状二维电子气（2DEG）纳米结构复合超表面，它具有两种状态：具有大量表面谐振特性的集体态和具有元原子谐振特性的个体态。通过用电栅控制纳米级二维电子气的电子传输，在这种复合超表面中可以实现集体 - 个体态转换。与局限于元单元的传统谐振模式转换不同，这种态转换使谐振模式能够灵活地分布在整个超表面，导致模拟和实验传输光谱中频率偏移近99%。此外，这种机制可以有效抑制寄生模式并显著降低超表面的电容。由此，这种复合超表面能够通过高速调制有效地控制太赫兹波的传输特性。结果，在静态实验中观察到93%的调制深度，在动态实验中实现了高达3 GHz的调制正弦信号，同时 -3 dB带宽可达1 GHz。这种可调谐的集体 - 个体态转换在无线通信和编码成像中可能具有巨大的应用潜力。
