Enhanced reflection chiroptical effect of planar anisotropic chiral metamaterials placed on the interface of two media

The strong chiroptical effect is highly desirable and has a wide range of applications in biosensing, chiral catalysis, polarization tuning, and chiral photo detection. In this work, we find a simple method to enhance the reflection circular dichroism (CD_R) by placing the planar anisotropic chiral metamaterials (i.e., Z-shaped PACMs) on the interface of two media (i.e., Z-PCMI) with a large refractive index difference. The maximum reflection CD_R from the complex system can reach about 0.840 when the refractive index is set as n _top = 4.0 and n _bottom = 1.49, which is approximately three times larger than that of placing the Z-shaped PACMs directly on the substrate (i.e., Z-PCMS). While the minimum reflection CD_R is 0.157 when the refractive index is set as n _bottom = 1.49. So we can get a large available range of reflection CD_R from –0.840 to –0.157. Meanwhile, the transmission CD_T remains unchanged with the refractive index n _top increment. Our in-depth research indicates that the large reflection CD_R is derived from the difference of non-conversion components of the planar anisotropic chiral metamaterials' reflection matrices. In short, we provide a simple and practical method to enhance the chiroptical effect by changing the refractive index difference between two media without having to design a complex chiral structure. (paper)