Waveguide devices for the physics and applications of non-Hermitian Photonic systems

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04927
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 30020:Optical engineering and photon science-related
• Research Institution: Hiroshima University
• Principal Investigator: Kadoya Yutaka 広島大学, 先進理工系科学研究科(先), 教授 (90263730)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: non-Hermite / Photonics / Waveguide / Grating / Meta-surface

Outline of Final Research Achievements

The purpose of this study is to realize an optical device in which a bound state in the continuum (BIC) and an exceptional point (ExP) coexist, which are the features of non-Hermitian physics, in the structure of a waveguide equipped with a grating, and to demonstrate the theoretical prediction that these points can be controlled by the structural parameters of the device. We selected the terahertz band as the wavelength range and invented an asymmetric double-layer metal grating (DMG) structure that can realize the predictions, and theoretically confirmed that the BIC can be easily controlled. We also established a simple fabrication method of DMGs and demonstrated experimentally the operation by an efficient extraction of a totally-reflected wave. In addition, we obtained an idea of research on the relationship between ExP and propagation direction-selective couplers. The invented DMG structure is useful also for improving output of terahertz generators.

Free Research Field

光デバイス工学

Academic Significance and Societal Importance of the Research Achievements

近年注目を集める非エルミート物理は物理学的な興味にとどまらず，実デバイスにおける影響・利用の観点からも重要である．光学系においては，従来はほとんど認識されていなかったが，本研究で対象としたように導波路＋カプラ―という，いわばありふれた構造でも発現するため，その理解や制御方法の確立は工学的にも極めて重要である．本研究では実証には至らなかったが，容易な構造で制御ができることを示し，また構造の作製と動作検証までを行っており，光学デバイスにおける非エルミート物理の理解と応用に資する結果を得た．また，考案した構造はテラヘルツ波光源の高出力化にも資するものであり，社会的意義も大きい．