A nanostructure consisting of a periodic array of the letter G produces a luminescent pattern whose handedness depends on the chirality of the illuminating light.
Two objects have opposite handedness (or chirality) if their mirror images cannot be superimposed. This property is important in biology and chemistry, affecting, for example, the interactions among proteins. Circularly polarized light, too, can be left-handed or right-handed. These two chiralities have been shown to give rise to different plasmon modes in nanostructures.
Now, Ventsislav Valev and colleagues at Leuven, Hasselt and Limburg universities have demonstrated that the handedness of incoming light can change the handedness of the luminescent pattern produced by a plasmonic nanostructure1. The nanostructure consists of a repeated series of the block letter G in various orientations, and generates a second harmonic signal in the shape of a ratchet when illuminated with red light. The handedness of the ratchet can be controlled by the handedness of the red light.
The results are a unique example of chirality in non-linear optics, and show that the handedness of a material can be determined by illuminating it with a single chirality of polarized light.
References
Valev, V. K. et al. Plasmonic ratchet wheels: switching circular dichroism by arranging chiral nanostructures. Nano Lett. 10.1021/nl9021623 (2009).
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Segal, M. Gee whiz. Nature Nanotech (2009). https://doi.org/10.1038/nnano.2009.375
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DOI: https://doi.org/10.1038/nnano.2009.375
