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We review our recent studies on the design, fabrication, and experimental verification by angle-resolved reflection spectroscopy of topological photonic crystals (PhCs) and topologically protected edge modes in the mid-infrared frequency range. We adopted a sample design based on the symmetry reduction from the honeycomb lattice to the C6v-symmetric lattice to tune the frequencies of E1- and E2-symmetric eigenmodes on the gamma point of the Brillouin zone. In addition to topologically trivial and non-trivial band gaps, we also succeeded in observing double Dirac cones with an isotropic linear dispersion relation by accidental degeneracy of the E1- and E2-symmetric modes. Our specimens had simple structures of PhC slabs fabricated in SOI (silicon-on-insulator) wafers without under-etching of a sacrificial layer beneath the PhC. Therefore, the photonic band gaps are generally narrow due to the small contrast of refractive indexes. Nevertheless, we achieved a sufficiently wide band gap of 6% relative to the midgap frequency, which facilitated our observation of the edge modes. We also verified experimentally that the edge modes were linearly polarized on the gamma point due to the 1:1 mixture of the original left- and right-circular polarizations. All these experimental observations were achieved by using our home-made reflection measurement apparatus with a 0.3 degree angle resolution.

権利情報:

• Creative Commons BY Attribution 4.0 International
  

キーワード: Mid-IR, Topological Edge Mode, Photonic crystals, High-angle resolution

刊行年月日: 2025-10-15

出版者: Physical Society of Japan

掲載誌:

• Journal of the Physical Society of Japan (ISSN: 00319015) vol. 94 issue. 10 101004

研究助成金:

原稿種別: 出版者版 (Version of record)

MDR DOI:

公開URL: https://doi.org/10.7566/jpsj.94.101004

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更新時刻: 2026-02-11 08:30:03 +0900

MDRでの公開時刻: 2026-02-10 18:03:06 +0900