Su Chengshuai, Fu Ceji
Opt Express. 2021 Nov 22;29(24):39824-39837. doi: 10.1364/OE.444358.
Uniaxial hyperbolic materials enable excitation of phonon polaritons with utrahigh wavevectors that have been shown to be promising for many optical and thermal radiative applications and thus have attracted much attention recently. However, the characteristics of surface and volume phonon polaritons excited with uniaxial hyperbolic materials that exhibit in-plane anisotropy or in-plane isotropy have not been discussed thoroughly and some issues have so far remained elusive. In this paper, we conducted a comprehensive investigation on surface and volume phonon polaritons in a bulk or a thin slab of hexagonal boron nitride (hBN). We clarified the excitation, characteristics and topology of surface and volume phonon polaritons in such a uniaxial hyperbolic material. In particular, we showed that hyperbolic surface phonon polaritons (HSPhPs) can exist in the Type I hyperbolic band of hBN with confined wavevectors when the optic axis (OA) is parallel to the surface. For a thin hBN slab, we revealed a split of HSPhPs and a smooth transition between HSPhPs and HVPhPs in the Type II hyperbolic band. Furthermore, we also identified non-Dyakonov surface phonon polaritons excited without evanescent ordinary waves. These findings may extend the understanding of phonon polaritons in hyperbolic materials and offer new theoretical guidance for the design of infrared optical devices with hyperbolic materials.
单轴双曲材料能够激发具有超高波矢的声子极化激元，这些声子极化激元已被证明在许多光学和热辐射应用中具有潜力，因此最近受到了广泛关注。然而，对于具有面内各向异性或面内各向同性的单轴双曲材料所激发的表面和声子极化激元的特性，尚未进行深入讨论，到目前为止，一些问题仍然难以捉摸。在本文中，我们对六方氮化硼（hBN）体材料或薄板中的表面和声子极化激元进行了全面研究。我们阐明了这种单轴双曲材料中表面和声子极化激元的激发、特性和拓扑结构。特别是，我们表明当光轴（OA）平行于表面时，双曲表面声子极化激元（HSPhPs）可以存在于hBN的I型双曲带中，且波矢受限。对于薄hBN板，我们揭示了II型双曲带中HSPhPs的分裂以及HSPhPs和体声子极化激元（HVPhPs）之间的平滑过渡。此外，我们还确定了在没有倏逝寻常波的情况下激发的非狄亚科诺夫表面声子极化激元。这些发现可能会扩展对双曲材料中声子极化激元的理解，并为用双曲材料设计红外光学器件提供新的理论指导。
