chirality switching via rotation of bilayer fourfold meta-structure

Chiral effects have been observed from the interaction of chiral plasmonics nanostructures with light. such nanostructures enhance the chiral response of molecules and provide an ideal platform for biological and chemical sensing. here, we investigate the chiral switching effects of an array of subwavelength nanostructures with a unit cell composed of four double-layered nanostrips arranged to be rotationally symmetric. we observe chiral switching leading to a change in circular dichroism (cd) signature when the mutual angle between the first and second layer increases from 0° to 90° with respect to each other. this mutual angle can be manipulated to switch the handedness of the nanostructure and cause a change in the outgoing light. we also investigated the field distribution of each mode when circularly polarized light is normally incident into the structure. these modes can be categorized into longitudinal and transverse modes depending on the orientation of their dipole moments. the mode studies clearly show the nature of each plasmonics mode.