Study On Characteristics Of Optical Activity Of Chiral Micro-nano Structures

Chiral metamaterials,exhibiting giant gyrotropy,circular dichroism,optical activity and asymmetric transmission,have attracted growing attention in the scientific communities in recent years.As a remarkable charactristic of chiral metamaterials,asymmetric transmission effect is reciprocal and arises from polarization conversion dichroism,which is popular in the scientific research field.In this paper,we propose a bilayered chiral metamaterial,which consists of periodic metallic arrays of two L-shaped structures and a nanorod twisted on both sides of a dielectric slab.The FDTD simulated results show that even the structure is with chiral symmetry,an optical chirality breaking window arises within the asymmetric transmission pass band.After analyzing the plasmonic mode properties,we attribute the chirality breaking effect to the plasmonic analogue of electromagnetically induced transparency effect.The optical chirality breaking window can be modulated by changing the length of the nanorods.Moreover,the window is sensitive to the index change of the surrounding medium,and can be applied on the field of biosensor.