control of chemical reactions by the potential modulation with vibrational polaritons

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K21175
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 32:Physical chemistry, functional solid state chemistry, and related fields
• Research Institution: Nara Institute of Science and Technology
• Principal Investigator: Katsuki Hiroyuki 奈良先端科学技術大学院大学, 先端科学技術研究科, 准教授 (10390642)
• Project Period (FY): 2020-07-30 – 2022-03-31
• Keywords: 振動ポラリトン / マイクロキャビティ / 液晶分子

Outline of Final Research Achievements

We have prepared an optical cavity with ~10um long, and resonate the vibrational transition of liquid crystalline molecule and a mid-infrared cavity photon to form a new quasiparticle called vibrational polaritons. We discuss the influence of phase transition from isotropic to smectic A phase on the Rabi splitting parameter, based on the angle-dependent transmittance spectroscopy. We could successfully observe the strong coupling in both phases. The Rabi splitting parameter, which represents the intensity of light-matter interaction, is largest for smectic phase with electric field parallel to the molecular director axis. These results supports that the macroscopic collective transition dipole moment is formed as a result of the molecular alignment. Since the Rabi splitting determines the upper and lower polariton energy, such phenomena result in the shift of the transmission frequency of the microcavity. This phenomenon can be applied for the optical switching applications.

Free Research Field

コヒーレント制御、超高速分光

Academic Significance and Societal Importance of the Research Achievements

配向の揃った液晶分子をマイクロキャビティ内に閉じ込め、光子と分子振動の強結合状態（振動ポラリトン）を作成した。配向相において分子間の協調効果が働き、イソトロピック相と比較してラビ分裂パラメータが大きく増大することが確認された。また、吸収の偏光依存性とラビ分裂の大きさから、液晶の配向軸のばらつきについて見積もることができることが示された。また本結果は、振動ポラリトンを利用した化学反応制御への応用においても、分子の配向を揃えることでラビ分裂パラメータを増大させ、振動ポラリトンの効果を増幅できる可能性を示唆しており、化学反応への応用にも有効であると考えられる。