High circular dichroism through planar plasmonic metasurfaces and enhancement through surface plasmon resonances

Research on metasurfaces featuring high circular dichroism has been very active in the last decade, because of possible applications in various fields, such as spintronics, polarization optics and stereochemistry. Despite literature displaying various proposed geometries and methods, today it is hard to define an alternative choice combining high Circular Dichroism (CD), easy realization and robustness of performance. In this work, we show the design approach and first experimental demonstration of a planar plasmonic metamaterial based on a comma-shaped geometry, which can be used to obtain high CD. Our metasurface combines intrinsic chirality and enhancement effects due to high field localization. In particular, the relative correspondence between numerical analyses and experiments shows the possibility to tune the effects of Surface Plasmon Resonances to a certain extent. This is equivalent to the possibility of engineering stable peak values on specific wavelength ranges, even in the presence of geometrical non-idealities due to fabrication. Samples were built through standard top-down fabrication procedures, helped by the symmetry of the extrusion. The ease in implementation, combined with reliable performances, make our proposed metamaterial eligible for adoption for further research in high precision spectroscopy and optical manipulation at industrial scale.