Zheng Zebo, Jiang Jingyao, Xu Ningsheng, Wang Ximiao, Huang Wuchao, Ke Yanlin, Zhang Shouren, Chen Huanjun, Deng Shaozhi
State Key Laboratory of Optoelectronic Materials and Technologies, Guangdong Province Key Laboratory of Display Material and Technology, School of Electronics and Information Technology, Sun Yat-sen University, Sun Yat-sen, 510275, China.
Frontier Institute of Chip and System, Fudan University, Shanghai, 200433, China.
Adv Mater. 2022 Feb;34(6):e2104164. doi: 10.1002/adma.202104164. Epub 2021 Dec 23.
Hyperbolic phonon polaritons (HPhPs) sustained in polar van der Waals (vdW) crystals exhibit extraordinary confinement of long-wave electromagnetic fields to the deep subwavelength scale. In stark contrast to uniaxial vdW hyperbolic materials, recently emerged biaxial hyperbolic materials, such as α-MoO and α-V O , offer new degrees of freedom for controlling light in two-dimensions due to their distinctive in-plane hyperbolic dispersions. However, the control and focusing of these in-plane HPhPs remain elusive. Here, a versatile technique is proposed for launching, controlling, and focusing in-plane HPhPs in α-MoO with geometrically designed curved gold plasmonic antennas. It is found that the subwavelength manipulation and focusing behaviors are strongly dependent on the curvature of the antenna extremity. This strategy operates effectively in a broadband spectral region. These findings not only provide fundamental insights into the manipulation of light by biaxial hyperbolic crystals at the nanoscale but also open up new opportunities for planar nanophotonic applications.
在极性范德华（vdW）晶体中维持的双曲线型声子极化激元（HPhPs）将长波电磁场显著限制在深亚波长尺度。与单轴vdW双曲线型材料形成鲜明对比的是，最近出现的双轴双曲线型材料，如α-MoO和α-VO，由于其独特的面内双曲线型色散，为二维光控制提供了新的自由度。然而，这些面内HPhPs的控制和聚焦仍然难以实现。在此，提出了一种通用技术，用于通过几何设计的弯曲金等离子体天线在α-MoO中发射、控制和聚焦面内HPhPs。研究发现，亚波长操纵和聚焦行为强烈依赖于天线末端的曲率。该策略在宽带光谱区域有效运行。这些发现不仅为双轴双曲线型晶体在纳米尺度上操纵光提供了基本见解，也为平面纳米光子应用开辟了新机会。
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