Bui Huu Nguyen, Phi Ngoc Hung, Alsaadi Abdulrahman, Lee Jong-Wook
School of Electronics and Information, Information and Communication System-on-Chip (SoC) Research Center, Kyung Hee University, 1732 Deogyeong-daero, Giheung, Yongin, Gyeonggi 17104, Republic of Korea.
ACS Appl Mater Interfaces. 2022 Jun 3. doi: 10.1021/acsami.2c04823.
Lorentz reciprocity is a fundamental physical property limiting advanced wave propagation control. Previously, special materials and magnetic bias were used to break the reciprocity; however, the approaches are limited by the bulky and costly implementation. To achieve nonreciprocity without magnetic bias, space-time-modulated metamaterials have been investigated for far-field wave propagation control. The metamaterial can also support wave propagation based on near-field coupling between the periodically arranged unit cells, i.e., magneto-inductive waves (MIWs). Near-field wave propagation control via the metamaterial has various significant applications; nevertheless, the potential for near-field wave propagation control has not been fully explored. Therefore, it is necessary to investigate the potential of the space-time-modulated near-field metamaterial. This paper demonstrates nonreciprocal MIW propagation control using a space-time-modulated metamaterial. To achieve field manipulation, we propose a tunable unit cell suitable for creating a cavity mode at a deep subwavelength scale (∼λ/10). Spatial field modulation, achieved by breaking the translational symmetry of the unit cells, allows for the creation of reconfigurable waveguides on the metamaterial. Temporal field modulation, achieved by breaking the capacitive symmetry of the varactor, allows for direction-dependent transmission in the waveguide. This spatiotemporal modulation successfully achieves nonreciprocal wave propagation and frequency conversion, investigated under various conditions. The proposed space-time-modulated metamaterial may provide significant advances for a wide range of systems that require dynamic, nonreciprocal, near-field wave propagation control.
洛伦兹互易性是限制先进波传播控制的一种基本物理特性。此前，人们使用特殊材料和磁偏置来打破互易性；然而，这些方法受到体积庞大和成本高昂的实施方式的限制。为了在无磁偏置的情况下实现非互易性，人们研究了时空调制超材料用于远场波传播控制。这种超材料还可以基于周期性排列的单元之间的近场耦合来支持波传播，即磁感应波（MIW）。通过超材料进行近场波传播控制有各种重要应用；然而，近场波传播控制的潜力尚未得到充分探索。因此，有必要研究时空调制近场超材料的潜力。本文展示了使用时空调制超材料实现非互易磁感应波传播控制。为了实现场操纵，我们提出了一种可调谐单元，适用于在深亚波长尺度（约λ/10）上创建腔模。通过打破单元的平移对称性实现的空间场调制，允许在超材料上创建可重构波导。通过打破变容二极管的电容对称性实现的时间场调制，允许在波导中进行方向依赖的传输。这种时空调制成功地实现了非互易波传播和频率转换，并在各种条件下进行了研究。所提出的时空调制超材料可能为广泛需要动态、非互易、近场波传播控制的系统带来重大进展。
