近日，意大利CNR-纳米科学研究所和高等教育学院Miriam S. Vitiello团队实现了在拓扑绝缘体元元件中利用可调谐色散追踪太赫兹等离子体激元。该项研究成果发表在2025年8月26日出版的《光：科学与应用》杂志上。

二维材料中无质量载流子的集体振荡，即狄拉克等离子激元(DPPs) ，对于具有可调谐光响应的工程纳米光子器件具有至关重要的意义。然而，在纳米材料中定制DPP的光学特性是一项非常具有挑战性的任务，特别是在太赫兹（THz）频率下，DPP动量比自由空间光子的动量大一个数量级以上，并且DDP衰减很高。

研究组设想并演示了一种调整拓扑绝缘体超材料中DPP色散的策略。他们设计了横向耦合的线性元元件，由外延Bi₂Se₃制造，具有选定的耦合距离，目的是通过几何来调整其波向量。研究组通过相敏散射型扫描近场纳米显微镜发射并直接映射了耦合元原子内DPP的传播。研究组证明，可以通过改变元元件耦合距离来调节DPP波长，从而使间距为1μm的二聚体和三聚体中的极化子波矢量Re（k_p）增加高达20%，同时减少损耗和 >50%极化子衰减长度的增加。

附：英文原文

Title: Tracing terahertz plasmon polaritons with a tunable-by-design dispersion in topological insulator metaelements

Author: Viti, Leonardo, Schiattarella, Chiara, Sichert, Lucia, Wang, Zhengtianye, Law, Stephanie, Mitrofanov, Oleg, Vitiello, Miriam S.

Issue&Volume: 2025-08-26

Abstract: Collective oscillations of massless charge carriers in two-dimensional materials—Dirac plasmon polaritons (DPPs)—are of paramount importance for engineering nanophotonic devices with tunable optical response. However, tailoring the optical properties of DPPs in a nanomaterial is a very challenging task, particularly at terahertz (THz) frequencies, where the DPP momentum is more than one order of magnitude larger than that of the free-space photons, and DDP attenuation is high. Here, we conceive and demonstrate a strategy to tune the DPP dispersion in topological insulator metamaterials. We engineer laterally coupled linear metaelements, fabricated from epitaxial Bi2Se3, with selected coupling distances with the purpose to tune their wavevector, by geometry. We launch and directly map the propagation of DPPs confined within coupled meta-atoms via phase-sensitive scattering-type scanning near-field nanoscopy. We demonstrate that the DPP wavelength can be tuned by varying the metaelements coupling distance, resulting in up to a 20% increase of the polariton wavevector Re(kp) in dimers and triplets with a 1μm spacing, with reduced losses and a>50% increase of the polariton attenuation length.

DOI: 10.1038/s41377-025-01884-0

Source: https://www.nature.com/articles/s41377-025-01884-0