  We previously reported [Naruse, et al. Sci. Rep. 4, 6077, 2014] that the
geometrical randomness of disk-shaped silver nanoparticles, which exhibit high
reflection at near-infrared wavelengths, serves as the origin of a
particle-dependent localization and hierarchical distribution of optical
near-fields in the vicinity of the nanostructure. In this study, we show that
the induced polarizations are circular, particularly at resonant wavelengths.
We formulate optical near-field processes between nanostructures, accounting
for their polarizations and geometries, and attribute circular polarization to
the layout-dependent phase difference between the electrical susceptibilities
associated with longitudinal and transverse-electric components. This study
clarifies the fundamental optical properties of random nanostructured matter
and offers generic theoretical concepts for implementing nanoscale
polarizations of optical near-fields.
