Polarization-dispersive imaging spectrometer for scattering circular dichroism spectroscopy of single chiral nanostructures.

Circular dichroism spectroscopy is one of the most important tools in nanoscopic chiroptics. However, there is lack of simple, fast and reliable method for measuring the circular dichroism responses of single nanostructures. To tackle this issue, we report a polarization-dispersive imaging spectrometer which is capable of measuring the scattering circular dichroism response of a single chiral nanostructure with a single shot. Using this technique, we studied the scattering circular dichroism spectra of a model system, the vertically coupled plasmonic nanorod pair. Both experimental and theoretical results indicate that the polarization-dispersive spectrometer measures the imaginary part of nonlocal susceptibility of the structure. We further applied the technique to 3-dimensional Au nanorod structures assembled on DNA origami templates together with correlated scanning electron microscopic measurements. Rich chiroptical phenomena were unveiled at the single nanostructure level.