Near-field mapping has been widely used to study hyperbolic phonon-polaritons in van der Waals crystals. However, an accurate measurement of the polaritonic loss remains challenging because of the inherent complexity of the near-field signal and the substrate-mediated loss. Here we demonstrate that large-area monocrystalline gold flakes, an atomically flat low-loss substrate for image polaritons, provide a platform for precise near-field measurement of the complex propagation constant of polaritons in van der Waals crystals. As a topical example, we measure propagation loss of the image phonon-polaritons in hexagonal boron nitride, revealing that their normalized propagation length exhibits a parabolic spectral dependency. Furthermore, we show that image phonon-polaritons exhibit up to a twice longer normalized propagation length, while being 2.4 times more compressed compared to the case of the dielectric substrate. We conclude that the monocrystalline gold flakes provide a unique nanophotonic platform for probing and exploitation of the image modes in low-dimensional materials.
Bibliographical noteFunding Information:
Funding: This work was supported by the Basic Science Research Program through the National Research Foundation of Korea grant 2021R1I1A1A01057510 (to S.G.M.), Samsung Research Funding and Incubation Center of Samsung Electronics grant SRFC-IT1702-14 (to S.G.M. and M.S.J.), Korea Institute of Science and Technology grant 2E31532 (to D.K.H.), Elemental Strategy Initiative conducted by the Ministry of Education, Culture, Sports, Science, and Technology of Japan grant JPMXP0112101001 (to K.W. and T.T.), JSPS KAKENHI grants 19H05790 and JP20H00354 (to K.W. and T.T.), VILLUM FONDEN grant 16498 (to N.A.M.), and the BK21 FOUR Program through the National Research Foundation of Korea.
© 2022 The Authors, some rights reserved
PubMed: MeSH publication types
- Journal Article