Liu Kaizhen, Huang Guangyan, Li Xiang, Zhu Guangpeng, Du Wei, Wang Tao
Institute of Functional Nano & Soft Materials (FUNSOM), Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Soochow University, 199 Ren'ai Road, Suzhou, Jiangsu, 215123, P. R. China.
State Key Laboratory of Infrared Physics, Chinese Academy of Sciences, 500 Yutian Road, Shanghai, 200083, P. R. China.
Adv Mater. 2022 Feb;34(8):e2109088. doi: 10.1002/adma.202109088. Epub 2022 Jan 15.
Vibrational strong coupling (VSC), the strong coupling between optical resonances and the dipolar absorption of molecular vibrations at mid-infrared frequencies, holds the great potential for the development of ultrasensitive infrared spectroscopy, the modification of chemical properties of molecules, and the control of chemical reactions. In the realm of ultracompact VSC, there is a need to scale down the size of mid-infrared optical resonators and to elevate their optical field strength. Herein, by using single quartz micropillars as mid-infrared optical resonators, the strong coupling is demonstrated between surface phonon polariton (SPhP) resonances and molecular vibrations from far-field observation. The single quartz micropillars support sharp SPhP resonances with an ultrasmall mode volume, which strongly couples with the molecular vibrations of 4-nitrobenzyl alcohol (C H NO ) molecules featuring pronounced mode splitting and anticrossing dispersion. The coupling strength depends on the molecular concentration and reaches the strong coupling regime with only 7300 molecules. The findings pave the way for promoting the VSC sensitivity, miniaturing the VSC devices, and will boost the development of ultracompact mid-infrared spectroscopy and chemical reaction control devices.
振动强耦合（VSC）是指光学共振与中红外频率下分子振动的偶极吸收之间的强耦合，在超灵敏红外光谱学的发展、分子化学性质的改性以及化学反应的控制方面具有巨大潜力。在超紧凑型VSC领域，需要缩小中红外光学谐振器的尺寸并提高其光场强度。在此，通过使用单根石英微柱作为中红外光学谐振器，从远场观测中证明了表面声子极化激元（SPhP）共振与分子振动之间的强耦合。单根石英微柱支持具有超小模式体积的尖锐SPhP共振，其与4-硝基苄醇（C₇H₇NO₂）分子的分子振动强烈耦合，表现出明显的模式分裂和反交叉色散。耦合强度取决于分子浓度，仅7300个分子就能达到强耦合状态。这些发现为提高VSC灵敏度、缩小VSC器件尺寸铺平了道路，并将推动超紧凑型中红外光谱学和化学反应控制装置的发展。
