Optical Chirality from Dark-Field Illumination of Planar Plasmonic Nanostructures

Yongsop Hwang, Ben Hopkins*, Dapeng Wang, Arnan Mitchell, Timothy J. Davis, Jiao Lin, Xiao Cong Yuan

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    11 Citations (Scopus)


    Dark-field illumination is shown to make planar chiral nanoparticle arrangements exhibit circular dichroism in extinction, analogous to true chiral scatterers. Single oligomers, consisting rotationally symmetric arrangements of gold nanorods, are experimentally observed to exhibit circular dichrosim at their maximum scattering with strong agreement to numerical simulation. A dipole model is developed to show that this effect is caused by a difference in the projection of a nanorod onto the handed orientation of electric fields created by a circularly polarized dark-field normally incident on a glass-air interface. Owing to this geometric origin, the wavelength of the peak chiral response is experimentally shown to shift depending on the separation between nanoparticles. All presented oligomers have physical dimensions less than the operating wavelength, and the applicable extension to closely packed planar arrays of oligomers is demonstrated to amplify the magnitude of circular dichroism. This realization of strong chirality in these oligomers demonstrates a new path to engineer optical chirality from planar devices using dark-field illumination.

    Original languageEnglish
    Article number1700216
    JournalLaser and Photonics Reviews
    Issue number6
    Publication statusPublished - Nov 2017


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