Hexagonal boron nitride has been proposed as an excellent candidate to achieve subwavelength infrared light manipulation owing to its polar lattice structure, enabling excitation of low-loss phonon polaritons with hyperbolic dispersion. We show that strongly subwavelength hexagonal boron nitride planar nanostructures can exhibit ultra-confined resonances and local field enhancement. We investigate strong light-matter interaction in these nanoscale structures via photo-induced force microscopy, scattering-type scanning near-field optical microscopy, and Fourier transform infrared spectroscopy, with excellent agreement with numerical simulations. We design optical nano-dipole antennas and directly image the fields when bright- or dark-mode resonances are excited. These modes are deep subwavelength, and strikingly, they can be supported by arbitrarily small structures. We believe that phonon polaritons in hexagonal boron nitride can play for infrared light a role similar to that of plasmons in noble metals at visible frequency, paving the way for a new class of efficient and highly miniaturized nanophotonic devices.

中文翻译：

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范德华纳米结构中的超限定中红外共振声子极化子。

六方氮化硼由于其极性晶格结构而被提议作为实现亚波长红外光操纵的极佳候选者，从而能够激发具有双曲线色散的低损耗声子极化子。我们表明强亚波长六角形氮化硼平面纳米结构可以表现出超限共振和局部场增强。我们通过光诱导力显微镜，散射型扫描近场光学显微镜和傅立叶变换红外光谱法研究了这些纳米级结构中强烈的物质相互作用，并与数值模拟取得了很好的一致性。我们设计了光学纳米偶极天线，并在激发亮模式或暗模式谐振时直接对场成像。这些模式是深亚波长，它们可以由任意小的结构支撑。我们认为，六方氮化硼中的声子极化子可以在可见光下对红外光起到与贵金属中的等离激元类似的作用，从而为新型的高效，高度小型化的纳米光子器件铺平了道路。