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Sci Adv. 2016 Mar 11;2(3):e1501349. doi: 10.1126/sciadv.1501349. eCollection 2016 Mar.

Resolving enantiomers using the optical angular momentum of twisted light.

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Division Molecular Imaging and Photonics, Department of Chemistry, KU Leuven (University of Leuven), Celestijnenlaan 200D, Box 2425, 3001 Leuven, Belgium.


Circular dichroism and optical rotation are crucial for the characterization of chiral molecules and are of importance to the study of pharmaceutical drugs, proteins, DNA, and many others. These techniques are based on the different interactions of enantiomers with circularly polarized components of plane wave light that carries spin angular momentum (SAM). For light carrying orbital angular momentum (OAM), for example, twisted or helical light, the consensus is that it cannot engage with the chirality of a molecular system as previous studies failed to demonstrate an interaction between optical OAM and chiral molecules. Using unique nanoparticle aggregates, we prove that optical OAM can engage with materials' chirality and discriminate between enantiomers. Further, theoretical results show that compared to circular dichroism, mainly based on magnetic dipole contributions, the OAM analog helical dichroism (HD) is critically dependent on fundamentally different chiral electric quadrupole contributions. Our work opens new venues to study chirality and can find application in sensing and chiral spectroscopy.


Optics; chirality; twisted light

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