Circular dichroism effect in a double-layer dolmen array nanostructure.

Chiral plasmonic nanostructures have been studied widely in past years and have various applications in biological sensing, negative refractive indexing, and analytical chemistry. Dolmen is also a commonly used nanostructure in many recent research papers. By placing dolmens in different directions and forming a double-layer dolmen array (DLDA), a new nanostructure with good circular dichroism (CD) effect is designed in this paper. We get up to the maximum of 0.5 of CD effect through numerical simulation. Among three obvious resonance wavelengths of CD effect, magnetic dipole resonance appears in two of them and contributes to the origin of a strong CD effect. In these different coupling modes, the strongest one locating at the largest wavelength is the result of a big magnetic dipolar resonance generated by circulation current in two layers of dolmen together, and the second strongest CD effect is caused by individual magnetic dipolar resonance in the opposite direction located in each layer. At the weakest one, the circulation current disappears and only a regular electric dipolar resonance appears. This simulation result shows that magnetic dipolar resonance of plasmonic nanostructure could create a strong CD effect, and much more effectively in the DLDA we propose. The results can help us in designing novel chiral optical nanostructures and provide applications in the interactions between photons and electrons.