Magnetic Control of the Plasmonic Chirality in Gold Helicoids

Chiral plasmonic nanostructures have facilitated a promising method for manipulating the polarization state of light. While a precise structural modification at the nanometer-scale-level could offer chiroptic responses at various wavelength ranges, a system that allows fast response control of a given structure has been required. In this study, we constructed uniformly arranged chiral gold helicoids with cobalt thin-film deposition that exhibited a strong chiroptic response with magnetic controllability. Tunable circular dichroism (CD) values from 0.9 degrees to 1.5 degrees at 550 nm wavelength were achieved by reversing the magnetic field direction. In addition, a magnetic circular dichroism (MCD) study revealed that the gap structure and size-related surface plasmon resonance induced MCD peaks. We demonstrated the transmitted color modulation, where the color dynamically changed from green-to-red, by controlling the field strength and polarizer axis. We believe current work broadens our understanding of magnetoplasmonic nanostructure and expands its potential applicability in optoelectronics or optical-communications.