扭曲纳米棒中杂化四极等离激元模式的手性二色性
Helical dichroism for hybridized quadrupole plasmon modes in twisted nanorods
AI总结：
本文揭示尺寸小于波长的扭曲纳米棒二聚体通过四极等离激元杂化产生显著手性二色性，且该效应源于轨道角动量而非自旋角动量。
摘要：
手性二色性（HD）源于手性等离激元结构与携带轨道角动量（OAM）的左、右涡旋光之间的相互作用，因其在基础物理和应用中的重要意义而受到多个学科领域的广泛关注。然而，HD与所激发的等离激元模式之间的精确关系仍不明确。由于对OAM光的弱手性光学响应，手性结构需要具有大于入射光波长的尺寸才能获得可观测的HD信号，这导致高阶等离激元模式的复杂叠加。在本工作中，我们揭示了一种尺寸小于入射光波长的简单扭曲纳米棒二聚体，由于纳米棒中激发的四极等离激元模式之间的强耦合以及随后的等离激元杂化，表现出显著的手性二色性。在与两个杂化四极模式对应的不同共振波长处，测量到了正、负HD响应，与计算结果吻合良好。HD的这种光谱行为明显不同于基于光自旋角动量（SAM）的圆二色性（CD），表明四极HD源于OAM而非SAM。这些发现为更深入地理解涉及角动量的光与物质相互作用铺平了道路。
英文摘要：
Helical dichroism (HD), originating from the interplay between chiral plasmonic structures and left and right vortex light carrying orbital angular momentum (OAM), has attracted significant attention across various disciplines owing to its implications in fundamental physics and applications. However, the precise relationship between HD and the excited plasmon modes remains elusive. Owing to the weak chiroptical response to OAM light, chiral structures have required dimensions larger than the incident light wavelength to obtain observable HD signals, resulting in complex superpositions of higher-order plasmon modes. In this work, we reveal that a simple twisted nanorod dimer with a size smaller than the incident light wavelength, exhibits remarkable HD due to the strong coupling between quadrupole plasmon modes excited in the nanorods, followed by the plasmon hybridization. Positive and negative HD responses were measured at different resonance wavelengths corresponding to two hybridized quadrupole modes, in good agreement with the calculated results. This spectral behavior of the HD is clearly different from that of the circular dichroism (CD) based on spin angular momentum (SAM) of light, indicating that the quadrupole HD arises from the OAM rather than the SAM. These findings pave the way for a deeper understanding of light-matter interactions concerning angular momentum.
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