Phillips Cassandra, Gilburd Leonid, Xu Xiaoji G, Walker Gilbert C
Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada.
Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, United States.
J Phys Chem Lett. 2019 Sep 5;10(17):4851-4856. doi: 10.1021/acs.jpclett.9b01829. Epub 2019 Aug 12.
Phonon polaritons (PhPs) are quasiparticles created by coupling of photons to polar lattice vibrations. Previously, PhPs have been observed as both surface and volume confined waves. The dispersion of the polariton depends strongly on the nature of the material. Volume polaritons show asymptotic behavior near the longitudinal optical phonon frequency of the material, whereas surface polaritons instead approach the surface phonon frequency. Boron nitride nanotubes (BNNTs) were found to exhibit the dispersion of volume modes below the surface phonon frequency. However, around and above the surface phonon frequency, the behavior becomes that of a surface wave with an amplified near-field response. These findings improve our understanding of photonics within BNNTs and suggest potential applications that take advantage of the high fields and density of states in that spectral region.
声子极化激元（PhPs）是通过光子与极性晶格振动耦合产生的准粒子。此前，人们已观察到PhPs既表现为表面受限波，也表现为体受限波。极化激元的色散强烈依赖于材料的性质。体极化激元在材料的纵向光学声子频率附近呈现渐近行为，而表面极化激元则趋近于表面声子频率。人们发现氮化硼纳米管（BNNTs）在低于表面声子频率时表现出体模色散。然而，在表面声子频率及其以上，其行为变为具有放大近场响应的表面波。这些发现增进了我们对BNNTs内光子学的理解，并暗示了利用该光谱区域的高场和态密度的潜在应用。
