Alfaro-Mozaz F J, Rodrigo S G, Vélez S, Dolado I, Govyadinov A, Alonso-González P, Casanova F, Hueso L E, Martín-Moreno L, Hillenbrand R, Nikitin A Y
CIC nanoGUNE BRTA, 20018 Donostia-San Sebastián, Spain.
Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, 50009 Zaragoza, Spain.
Nano Lett. 2021 Sep 8;21(17):7109-7115. doi: 10.1021/acs.nanolett.1c01452. Epub 2021 Aug 20.
Phonon polaritons (PhPs) in van der Waals (vdW) crystal slabs enable nanoscale infrared light manipulation. Specifically, periodically structured vdW slabs behave as polaritonic crystals (vdW-PCs), where the polaritons form Bloch modes. Because the polariton wavelengths are smaller than that of light, conventional far-field spectroscopy does not allow for a complete characterization of vdW-PCs or for revealing their band structure. Here, we perform hyperspectral infrared nanoimaging and analysis of PhPs in a vdW-PC slab made of h-BN. We demonstrate that infrared spectra recorded at individual spatial positions within the unit cell of the vdW-PC can be associated with its band structure and local density of photonic states (LDOS). We thus introduce hyperspectral infrared nanoimaging as a tool for the comprehensive analysis of polaritonic crystals, which could find applications in the reconstruction of complex polaritonic dispersion surfaces in momentum-frequency space or for exploring exotic electromagnetic modes in topological photonic structures.
范德华（vdW）晶体平板中的声子极化激元（PhPs）能够实现纳米级红外光操控。具体而言，周期性结构的vdW平板表现为极化激元晶体（vdW-PCs），其中极化激元形成布洛赫模式。由于极化激元波长小于光的波长，传统远场光谱法无法对vdW-PCs进行完整表征，也无法揭示其能带结构。在此，我们对由h-BN制成的vdW-PC平板中的PhPs进行了高光谱红外纳米成像和分析。我们证明，在vdW-PC晶胞内各个空间位置记录的红外光谱可与其能带结构及光子态局域密度（LDOS）相关联。因此，我们引入高光谱红外纳米成像作为一种用于全面分析极化激元晶体的工具，它可应用于动量-频率空间中复杂极化激元色散面的重构，或用于探索拓扑光子结构中的奇异电磁模式。
