1 research outputs found
Decoding Polarization in a Single Achiral Gold Nanostructure from Emitted Far-Field Radiation
The
emergence of optical chirality in the light emitted from plasmonic
nanostructures is commonly associated with their geometrical chirality.
Although it has been demonstrated that even achiral structures can
exhibit chiral near-fields, the existence of chiroptical far-field
responses of such structures is widely neglected. In this paper, we
present a detailed analysis of the polarization state in a single
planar achiral plasmonic nanostructure that sustains more than one
prominent plasmon mode. In consideration of the relative phase, the
superposition of the fields associated with these modes determines
the polarization state of the emitted light in the far-field. Supported
by simulations of the surface charge distribution of the particle,
we show that the polarization state of the emitted light is already
determined in the near-field. The chiroptical far-field responses
are analyzed by polarized single-particle dark-field scattering spectroscopy.
We introduce an analytical model that enables us to obtain the polarization
information from the spectra of structures with dipolar resonances
taken under unpolarized illumination. The same principle is confirmed
in polarimetric spectroscopy measurements on rhomboids with systematically
varied angles, therefore, introducing increasing values of geometrical
chirality to the structures. The agreement between the calculation
and measurement demonstrates the general validity of our model for
both chiral and achiral structures