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arXiv 2301.01248physics.optics
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从远场测量捕获近场圆二色性增强

Capturing near-field circular dichroism enhancements from far-field measurements

Jorge Olmos-Trigo, Jon Lasa-Alonso, Iker Gómez-Viloria, Gabriel Molina-Terriza, Aitzol García-Etxarri

摘要:

分子圆二色性(CD)光谱面临着显着的局限性,由于手性轻物质相互作用的固有弱点。在这种观点中,谐振光学天线构成了一个有前途的解决方案,这个问题,因为它们可以被调谐,以增加CD增强因子,fCD,描述与给定的螺旋度相关的散射体的电磁近场增强的幅度。在这里,我们推导出一个精确的多极展开的fCD,这是有效的推导出集成的近场CD增强的手性分子在一般照明条件下的任何大小和形状的散射体的存在下。基于我们的分析结果,我们表明,近场fCD因子可以与可以在远场计算的幅度相关,即,散射截面和螺旋度期望值。此外,我们表明,在无损圆柱对称样品的情况下,近场fCD因子可以推断实验仅从两个远场测量在特定的散射角。我们的贡献铺平了道路,能够提高分子CD光谱设备的实验表征。

英文摘要:

Molecular Circular dichroism (CD) spectroscopy faces significant limitations due to the inherent weakness of chiroptical light-matter interactions. In this view, resonant optical antennas constitute a promising solution to this problem since they can be tuned to increase the CD enhancement factor, fCD, a magnitude describing the electromagnetic near-field enhancement of scatterers associated with a given helicity. Here, we derive an exact multipolar expansion of fCD, which is valid to deduce the integrated near-field CD enhancements of chiral molecules in the presence of scatterers of any size and shape under general illumination conditions. Based on our analytical findings, we show that the near-field fCD factor can be related to magnitudes that can be computed in the far-field, i.e., the scattering cross-section and the helicity expectation value. Moreover, we show that in the case of lossless cylindrically symmetric samples, the near-field fCD factor can be inferred experimentally only from two far-field measurements at specific scattering angles. Our contribution paves the way for the experimental characterization of devices capable of enhancing molecular CD spectroscopy.

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