Chirality of stacked plasmonic nanorods

The Optical activity of a stacked of Au nanorods based on the coupled dipole approximation is studied thoroughly. It is shown that chirality strongly depends on the spatial phase retardation and the couplings' strength between two plasmonic nanorods. The optimum vertical space for obtaining a tradeoff between phase retardation and the couplings' strength is determined. Moreover, it is shown that by increasing the length of the nanorods, the circular dichroism spectrum experiences a red shift and its amplitude linearly increases. The theoretical results are well supported by the numerical computation.