Enhanced chiroptical activity with slotted high refractive index dielectric nanodisks

Abstract

In this paper we employ finite difference time-domain (FDTD) calculations to demonstrate the enhancement of chiroptical activity in high refractive index dielectric slotted nanodisks. The chiral enhancement mechanism consists of pairing the electric and magnetic modes of the slit cavity with the resonances of the rest of the disk, i.e., the weak chiroptical activity (∼10−1) inside the chiral gap region (which is chiral itself) is enhanced through the interaction with the electric and magnetic resonances in the nanodisk. These results are extended to a two-dimensional periodic arrangement of slotted nanosdisks forming a metasurface. The chiral electromagnetic near field at the slotted region can be harnessed for increasing the asymmetry in energy absorption of circularly polarized light (CPL). This chiral enhancement makes this novel metasurface useful for sensing or to control the optical forces that can be exerted on chiral molecules placed in those slotted regions. The latter can be relevant to the pharmaceutical industry since distinct enantiomers of racemic drugs frequently exhibit different biological activities.