Credit: © 2009 ACS

An object possesses handedness (or chirality) if its mirror image cannot be superimposed on it. Circularly polarized light can also be left-handed or right-handed, and these two chiralities have been shown to give rise to different plasmon modes in nanostructures. Now, Ventsislav Valev and colleagues at the Katholieke Universiteit Leuven, Univerisity Hasselt and transnational University Limburg, all in Belgium, have demonstrated that the handedness of incoming light can change the handedness of the luminescent pattern produced by an array of plasmonic nanostructures (Nano Lett. 9, 3945–3948; 2009).

The array is made from G-shaped (right) or mirror-G-shaped (far right) gold nanostructures in various orientations. Yellow lines have been drawn around the shapes in these scanning electron micrographs to improve their visibility. The actual arrays used in the experiments consist of 3,333 × 3,333 nanostructures. When illuminated with red light, the array generates a ratchet-shaped second harmonic signal with a handedness that can be controlled by the handedness of the red light. The team can also measure the handedness of the material by illuminating it with a single chirality of polarized light, rather than the two chiralities needed in other approaches.