Optical Circular Conversion Dichroism via Heterogeneous Planar Nanoplasmonic Metasurface

Chirality as a physical phenomenon originating from lacking mirror symmetry in many natural substances exposes fascinating optical activities, including circular dichroism (CD) and optical circular conversion dichroism (O-CCD). While naturally occurring chiroptical properties are negligible in real substances, boosting these properties to significant levels is one of the main challenges for designing functional photonic and optoelectronic devices. Here, we introduce a new paradigm for the realization of planar metasurfaces with substantial O-CCD, reporting that considerable chiral effects of three-dimensional chiral structure are practically provided by feasible metasurfaces by picking out nanooscillators with strong near-field interaction, different optical properties including loss and radiation, and high overlap between their spectral positions. We apply this concept to heterogeneous nanoplasmonic structures, composed of L-pair of Au–Ag nanorods, as archetypical configurations for substantially raising dichroism compared to materially homogenous ones, i.e., Au–Au and Ag–Ag pairs with different length, respectively. The essential prerequisite for phase lag associated with the third dimension along lightwave propagation is compensated by proposed heterogeneity in metasurface design. Theoretical findings based on the simple hybridization model are adequately supported by the computational results.