Chiral Plasmonic Nanohelix: Circular Dichroism

Metal nanostructures with no mirror symmetry — helices, gammadions, DNA-templated nanoparticle assemblies — can absorb left- and right-circularly-polarized light differently even though gold itself has no molecular chirality. This simulator builds a helical chain of plasmonic gold nanospheres and solves a self-consistent discrete-dipole (coupled-dipole) model: each particle is a damped Lorentzian oscillator driven by the incident circular field and by the near-field radiation of every other particle. Flip the helix handedness, change the particle count and pitch, and sweep the driving wavelength to watch the induced dipole pattern and the resulting plasmonic circular-dichroism spectrum, CD(λ) = A(LCP) − A(RCP), respond exactly as it does for a real chiral plasmonic nanostructure.