Jiang Jingyao, Zheng Zebo, Huang Wuchao, Cao Zhaolong, Xu Ningsheng, Chen Huanjun, Deng Shaozhi
State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, and School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, China.
Nano Lett. 2025 Jul 9;25(27):10953-10961. doi: 10.1021/acs.nanolett.5c02388. Epub 2025 Jun 18.
Hyperbolic phonon polaritons (HPhPs) in polar van der Waals crystals, such as α-MoO and α-VO, enable deep subwavelength light confinement and in-plane manipulation via hyperbolic dispersion, yet momentum mismatch hinders efficient excitation. We present a far-field method to excite in-plane HPhPs using plasmonic gold nanorods. Surface plasmon resonance (SPPR) in nanorods mediates strong interactions between free-space waves and HPhPs in α-MoO. Excitation efficiency is highly sensitive to nanorod length and angular orientation relative to the [100] crystal axis of α-MoO. Maximum HPhP near-field intensity is achieved when the nanorods are aligned to optimize coupling with the anisotropic polaritonic modes, with efficiency closely linked to the resonance conditions of the plasmonic antennas. Numerical designs are corroborated well with near-field optical characterizations. Therefore, our approach establishes a platform to study interactions between plasmonic antennas and anisotropic polaritons, advancing controlled manipulation of in-plane polaritonic modes in van der Waals materials.
诸如α-MoO₃和α-V₂O₅等极性范德华晶体中的双曲型声子极化激元（HPhPs），能够通过双曲型色散实现深亚波长光限制和面内操纵，然而动量失配阻碍了有效激发。我们提出了一种利用等离子体金纳米棒激发面内HPhPs的远场方法。纳米棒中的表面等离子体共振（SPPR）介导了自由空间波与α-MoO₃中的HPhPs之间的强相互作用。激发效率对纳米棒长度以及相对于α-MoO₃[100]晶轴的角取向高度敏感。当纳米棒排列以优化与各向异性极化激元模式的耦合时，可实现最大的HPhP近场强度，其效率与等离子体天线的共振条件密切相关。数值设计与近场光学表征结果吻合良好。因此，我们的方法建立了一个研究等离子体天线与各向异性极化激元之间相互作用的平台，推动了对范德华材料中面内极化激元模式的可控操纵。
