Circular Dichroism Induced by the Coupling between Surface Plasmon Polaritons and Localized Surface Plasmon Resonances in a Double-Layer Complementary Nanostructure

Circular dichroism (CD) spectroscopy is an important technique for detecting and identifying chiral molecules in the fields of chemistry, biology, and other life sciences. Artificial plasmonic nanostructures exhibit considerable CD effects, but the preparation of 3D and multilayer chiral structures that exhibit large CD signals is usually difficult. Strong CD effects and simple fabrication processes are necessary. In this study, double-layer complementary nanostructures (DLCNs) that can generate prominent CD signals are prepared with a simple experimental method. Numerical calculations show that the physical mechanism underlying the CD effect is the coupling between localized surface plasmon resonances excited in complementary nanostructures and surface plasmon polaritons excited on a metal nanofilm under left-circularly polarized and right-circularly polarized light illuminations. The CD effect can be tuned by changing the parameter of the DLCN array. Results provide a way to generate CD effects with spatially complementary nanostructures and may provide an avenue for the chiral manipulation of light. These chiral nanostructures can be fabricated through simple methods, have considerable CD signals, and provide insights into the chiral optical response, providing novel tools for the design of chiral optoelectronic devices.