Xu Jie, Xiao Sanshui, He Panpan, Wang Yazhou, Shen Yun, Hong Lujun, Luo Yamei, He Bing
Opt Express. 2022 Jan 31;30(3):3941-3953. doi: 10.1364/OE.447874.
Unidirectionally propagating wave (UPW) such as surface magnetoplasmon (SMP) has been a research hotspot in the last decades. In the study of the UPW, metals are usually treated as perfect electric conductors (PECs). However, it was reported that the transverse resonance condition induced by the PEC wall(s) may significantly narrow up the complete one-way propagation (COWP) band. In this paper, ultra-broadband one-way waveguides are built by utilizing the epsilon-negative (ENG) metamaterial (MM) and/or the perfect magnetic conductor (PMC) boundary. In both cases, the total bandwidth of the COWP bands are efficiently enlarged by more than three times than the one in the original metal-dielectric-semiconductor-metal structure. Moreover, the one-way waveguides consisting of gradient-index metamaterial are proposed to achieve broadband truly rainbow trapping (TRT). In the full-wave simulations, clear broadband TRT without back reflection is observed in terahertz regime. Besides, giant electric field enhancement is achieved in a PMC-based one-way structure, and the amplitude of the electric field is enormously enhanced by five orders of magnitude. Our findings are beneficial for researches on broadband terahertz communication, energy harvesting and strong-field devices.
诸如表面磁等离子体激元（SMP）之类的单向传播波（UPW）在过去几十年中一直是研究热点。在单向传播波的研究中，金属通常被视为理想电导体（PEC）。然而，据报道，由PEC壁引起的横向共振条件可能会显著缩小完全单向传播（COWP）带宽。在本文中，通过利用负介电常数（ENG）超材料（MM）和/或理想磁导体（PMC）边界构建了超宽带单向波导。在这两种情况下，COWP带的总带宽都比原始金属 - 电介质 - 半导体 - 金属结构中的带宽有效扩大了三倍以上。此外，还提出了由梯度折射率超材料组成的单向波导，以实现宽带真彩虹俘获（TRT）。在全波模拟中，在太赫兹波段观察到了清晰的无背反射宽带TRT。此外，在基于PMC的单向结构中实现了巨大的电场增强，电场幅度极大地增强了五个数量级。我们的研究结果有利于宽带太赫兹通信、能量收集和强场器件的研究。
