Multiple truly topological unidirectional surface magnetoplasmons at terahertz frequencies
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arXiv
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| Auteurs principaux: | , , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866910960753573888 |
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| author | Fan, Shengquan Guo, Tianjing Zhou, Binbin Xu, Jie Deng, Xiaohua Lei, Jiangtao Shen, Yun Fu, Meicheng Tsakmakidis, Kosmas L. Hong, Lujun |
| author_facet | Fan, Shengquan Guo, Tianjing Zhou, Binbin Xu, Jie Deng, Xiaohua Lei, Jiangtao Shen, Yun Fu, Meicheng Tsakmakidis, Kosmas L. Hong, Lujun |
| contents | Unidirectional propagation based on surface magnetoplasmons (SMPs) has recently been realized at the interface of magnetized semiconductors. However, usually SMPs lose their unidirectionality due to non-local effects, especially in the lower trivial bandgap of such structures. More recently, a truly unidirectional SMP (USMP) has been demonstrated in the upper topological non-trivial bandgap, but it supports only a single USMP, limiting its functionality. In this work, we present a fundamental physical model for multiple, robust, truly topological USMP modes at terahertz (THz) frequencies, realized in a semiconductor-dielectric-semiconductor (SDS) slab waveguide under opposing external magnetic fields. We analytically derive the dispersion properties of the SMPs and perform numerical analysis in both local and non-local models. Our results show that the SDS waveguide supports two truly (even and odd) USMP modes in the upper topological non-trivial bandgap. Exploiting these two modes, we demonstrate unidirectional SMP multimode interference (USMMI), being highly robust and immune to backscattering, overcoming the back-reflection issue in conventional bidirectional waveguides. To demonstrate the usefullness of this approach, we numerically realize a frequency- and magnetically-tunable arbitrary-ratio splitter based on this robust USMMI, enabling multimode conversion. We, further, identify a unique index-near-zero (INZ) odd USMP mode in the SDS waveguide, distinct from conventional semiconductor-dielectric-metal waveguides. Leveraging this INZ mode, we achieve phase modulation with a phase shift from -$π$ to $π$. Our work expands the manipulation of topological waves and enriches the field of truly non-reciprocal topological physics for practical device applications. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2501_09376 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Multiple truly topological unidirectional surface magnetoplasmons at terahertz frequencies Fan, Shengquan Guo, Tianjing Zhou, Binbin Xu, Jie Deng, Xiaohua Lei, Jiangtao Shen, Yun Fu, Meicheng Tsakmakidis, Kosmas L. Hong, Lujun Optics Unidirectional propagation based on surface magnetoplasmons (SMPs) has recently been realized at the interface of magnetized semiconductors. However, usually SMPs lose their unidirectionality due to non-local effects, especially in the lower trivial bandgap of such structures. More recently, a truly unidirectional SMP (USMP) has been demonstrated in the upper topological non-trivial bandgap, but it supports only a single USMP, limiting its functionality. In this work, we present a fundamental physical model for multiple, robust, truly topological USMP modes at terahertz (THz) frequencies, realized in a semiconductor-dielectric-semiconductor (SDS) slab waveguide under opposing external magnetic fields. We analytically derive the dispersion properties of the SMPs and perform numerical analysis in both local and non-local models. Our results show that the SDS waveguide supports two truly (even and odd) USMP modes in the upper topological non-trivial bandgap. Exploiting these two modes, we demonstrate unidirectional SMP multimode interference (USMMI), being highly robust and immune to backscattering, overcoming the back-reflection issue in conventional bidirectional waveguides. To demonstrate the usefullness of this approach, we numerically realize a frequency- and magnetically-tunable arbitrary-ratio splitter based on this robust USMMI, enabling multimode conversion. We, further, identify a unique index-near-zero (INZ) odd USMP mode in the SDS waveguide, distinct from conventional semiconductor-dielectric-metal waveguides. Leveraging this INZ mode, we achieve phase modulation with a phase shift from -$π$ to $π$. Our work expands the manipulation of topological waves and enriches the field of truly non-reciprocal topological physics for practical device applications. |
| title | Multiple truly topological unidirectional surface magnetoplasmons at terahertz frequencies |
| topic | Optics |
| url | https://arxiv.org/abs/2501.09376 |