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Circular dichroism (CD) is widely used to detect structural chirality in molecules and nanostructures, yet in anisotropic systems its interpretation can be obscured by polarization conversion. To clarify the physical origin of CD in three-dimensional twisted gold nanorod dimers (TNDs), we experimentally retrieve the full complex Jones matrix in the circular-polarization basis for multiple twist angles, where conversion appears as off-diagonal elements. The TNDs exhibit a strong asymmetry between the diagonal elements while maintaining nearly symmetric conversion amplitudes, yielding pronounced intrinsic CD with suppressed circular conversion dichroism (CCD). A coupled-oscillator model reproduces this Jones-matrix symmetry and explains the twist-angle dependence, establishing a matrix-resolved criterion for distinguishing intrinsic CD from conversion-channel contributions (CCDs) in anisotropic nanophotonic systems.
Onodera et al. (Wed,) studied this question.