Observation of helical edge states in topological photonic crystals

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K14634
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
• Research Institution: Kyoto University
• Principal Investigator: Inose Yuta 京都大学, 理学研究科, 特定助教 (90634501)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: トポロジカルフォトニクス / フォトニック結晶 / 共鳴トンネルダイオード発振器 / テラヘルツ

Outline of Final Research Achievements

We prepared two kinds of photonic crystals that have band gaps near 1 THz, and observed band inversion due to differences in the topology using terahertz time-domain spectroscopy. We directly observed the periodic spatial image of the electric field generated in the photonic crystals by real-time terahertz near-field microscope. However, our approach didn't reach an adequate level of signal intensity to get the evident image at the boundary of the two structures because of the lack of coupling efficiency of external light into the samples.
In addition, we conducted the behavior of a combined device consisting of compact terahertz light source and photonic crystal. We demonstrated that the spectrum of radiated terahertz light becomes narrow and stable under the influence of self-injection into the light source.

Free Research Field

フォトニック結晶、共鳴トンネルダイオード発振器

Academic Significance and Societal Importance of the Research Achievements

フォトニック結晶の特性は、スペクトル情報を通して評価されることが多い。本研究では電磁場の波動関数を直接観測したが、これは局在モードや導波モードなど光集積デバイスに用いられる各要素を精密に評価する手法としての応用が期待できる。
また、小型テラヘルツ光源とフォトニック結晶の結合デバイスに関する検証は、将来的に社会実装が期待される高効率な光集積デバイスの創成に繋がる成果である。