Leveraging Superchiral Light for Manipulation of Optical Chirality in the Near-Field of Plasmonic Metamaterials

Methods for generating enhanced chiroptical response are of great importance in biological and biochemical applications primarily due to the ubiquitous presence of chiral substances in the organic world. Exhibiting an unprecedentedly strong chiroptical response, metamaterials are considered as a good candidate for achieving the highly sought after enhanced optical chirality. Here we demonstrate that optical chirality in the near-field of planar chiral metamaterials can be controlled by the so-called superchiral light composed by two counter-propagating beams of circularly polarized light (CPL) of the opposite handedness. In contrast with the scenario of single CPL excitation, continuous manipulation of optical chirality including the handedness selective enhancement and switching effect is observed. Moreover, the volumetric examination reveals that the enhanced optical chirality is much more delocalized, indicating a further improved accessibility for plasmonic nanostructure based enantiomeric sensing. Finally, we demonstrate the potential of the proposed optical chirality manipulation for optical information processing in a proof-of-concept study involving a coherent imaging system.