Circular Dichroism of Single Particles

Circular dichroism (CD) occurs in chiral molecules and nanostructures. It is manifested over a wide range of length scales, from molecules to crystals and large nanostructures. Being a weak phenomenon (typically a small fraction of absorption), CD is routinely measured on macroscopic quantities of matter in solutions, crystals, or arrays of fabricated meta-particles. These ensemble-averaged measurements mask the sensitivity of CD to small structural variations between individual nano-objects or to the possible coexistence of opposite enantiomers in the ensemble. We have developed far field extinction microcopy, which enables sensitive CD measurement on individual nano-objects, encompassing dramatic suppression of linear optical activity artifacts. Here, we report on CD of both chiral shaped plasmonic nanostructures (gold Gammadions) and achiral shaped inorganic nanocrystals having a chiral crystal lattice (HgS). CD spectra and spatial mapping were measured. Simulations on Gammadions, mimicking the experim...