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When a low-dimensional polaritonic material is placed in proximity to a highly conductive metal, polariton modes couple to their images in the metal, forming highly compressed image polaritons. So far, near-field mapping has been used to observe such modes in graphene and hexagonal boron nitride (hBN). However, an accurate measurement of their intrinsic loss remains challenging because of the inherent complexity of the near-field signal, particularly for the hyperbolic phonon-polaritons. Here we demonstrate that monocrystalline gold flakes, an atomically-flat low-loss substrate for image modes, provide a platform for precise near-field measurement of the complex propagation constant of image polaritons. As a topical example, we measure dispersion of the hyperbolic image phonon-polaritons (HIP) in hBN, revealing that their normalized propagation length exhibits a parabolic spectral dependency. At the frequency of the maximal propagation, image modes exhibit nearly two times lower normalized loss, while being 2.4 times more compressed compared to the phonon-polaritons in hBN on a dielectric substrate. We conclude that the image phonon-polaritons in van der Waals crystals provide a unique nanophotonic platform where strong light-matter interaction and wave phenomena can be harnessed at the same time.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: Near-field mapping, phonon-polaritons, van der Waals crystals

刊行年月日: 2022-07-15

出版者: American Association for the Advancement of Science (AAAS)

掲載誌:

• Science Advances (ISSN: 23752548) vol. 8 issue. 28

研究助成金:

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.1126/sciadv.abn0627

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更新時刻: 2025-03-03 16:30:36 +0900

MDRでの公開時刻: 2025-03-03 16:30:36 +0900