Circular dichroism enhancement induced by surface plasmons in the structure of a metallic grating coated by chiral TDBCs

Abstract

We investigate the enhancement of the circular dichroism (CD) spectrum in a metallic grating by coating it with chiral TDBCs. Using the finite difference time domain method, we obtain reflection spectra and CD spectra. The amplification of TDBCs chirality is achieved through the excitation of both surface plasmon polaritons (SPPs) and localized surface plasmons (LSPs) in the Ag grating structure. Our results indicate that, compared to chiral TDBCs alone, the enhancement factor of chiral TDBCs coated on the metallic grating can reach up to 200 times. The coupling between chiral TDBCs and electromagnetic fields induced by SPPs and LSPs is tuned by both the period and groove thickness of the grating structure. Under certain conditions, strong coupling phenomena are observed, demonstrating a competitive relationship between the dissipation of our proposed structure and the coupling of electromagnetic fields and chiral TDBCs. The substantial amplification of the CD spectra suggests that our proposed structure provides a novel method to enhance the chirality of TDBCs experimentally.