Study of the mechanism of the interfacial Pockels effect and its application

2022 Fiscal Year Final Research Report

• Project/Area Number: 20H02659
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 30020:Optical engineering and photon science-related
• Research Institution: Tokyo University of Science
• Principal Investigator: Tokunaga Eiji 東京理科大学, 理学部第一部物理学科, 教授 (70242170)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: ポッケルス効果 / 水 / 界面 / 電気光学効果 / プラズモン / コヒーレント完全吸収 / 静的誘電率 / イオン液体

Outline of Final Research Achievements

Research was conducted to elucidate the mechanism of the Pockels effect of the electrode interface water and to develop its application. The Pockels coefficients of silver and Ti electrode interface water were evaluated by the shift of surface plasmon resonance peak and by the shift of interference structure due to surface oxide film, respectively, and the Pockels coefficient was shown to be smaller for noble metal interface water and larger for base metal interface water with oxide film. This is consistent with the electrode material dependence of the bulk water Pockels effect. The Pockels coefficients of liquids with larger static dielectric constants than water were also evaluated, and it was shown that the dielectric constant of the liquid does not correlate with the magnitude of the Pockels coefficient. Coherent perfect absorption, which can extract a huge optical modulation signal from the interfacial Pockels effect, was realized in various thin films.

Free Research Field

光物性　非線形光学

Academic Significance and Societal Importance of the Research Achievements

空間反転対称性が破れている2つの材料の界面は、電場に比例する屈折率変化であるポッケルス効果(1次の電気光学効果)が起こる必要条件を満たすが、実際に大きなポッケルス効果を発現する条件は未解明である。現在、酸化物透明電極の界面水が実用電気光学結晶よりも桁違いに大きいポッケルス係数を持つことが知られている。金属電極界面水のポッケルス係数が、酸化膜のできる金属で大きいことは水と電極表面の水素結合性の相互作用が重要であることを示唆し、大きな界面ポッケルス効果の条件解明のために意義深い。特にTi電極は酸化膜で保護され耐久性・耐腐食性が高いので、その界面水は紫外用光変調器への実用的可能性がある。