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arXiv · 2301.01248

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
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Abstract

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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Jorge Olmos-Trigo, Jon Lasa-Alonso, Iker Gómez-Viloria, Gabriel Molina-Terriza, Aitzol García-Etxarri. 2023-01-03. Capturing near-field circular dichroism enhancements from far-field measurements. https://arxiv.org/abs/2301.01248

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