  The near-field interaction of plasmonic nanostructures and chiral molecules
induces circular dichroism in achiral nanostructure. The induced circular
dichroism (ICD) strength is several orders greater than the molecular inherent
CD (MCD), and it generally appears at visual range (VR) where the CD signal is
easily detectable. Therefore, the ICD is considered as a potential method to
detect single molecular chirality. In this study, cross shaped nanohole (CSN)
is proposed for enhancing the MCD signal. The maximum enhancement of the
structure reached 450 folds of molecular inherent MCD. Through analysis of the
surface plasmon resonance mode, it is found that overlapping of the electric
dipole (ED) and magnetic dipole (MD) surface plasmon resonance (SPR) in CSN is
essential for the CD enhancement. Furthermore, we investigated the effects of
the thickness of structure, length of longer and shorter arms of nanohole, the
displacement of shorter arm of the nanohole and x period of CSN on the circular
dichroism enhancement, and found the enhancement factor and location of CD
enhancement peak to be tunable by the structural parameters
