Visualization of Plasmon Characteristics and Chiral Optical Fields Excited in Noble Metal Nanoplates

Plasmons excited in noble metal nanoparticles confine light and amplify the optical field in the vicinity of the nanoparticles. To design plasmonic fields for advanced applications, understanding of plasmons is indispensable. In this report, we describe near-field visualization of plasmons and chiral optical fields around noble metal nanoplates. Near-field transmission imaging revealed that the nanoplate exhibits multiple resonances and transmission images exhibit distinctive spatial features assignable to plasmonic wavefunctions. By using near-field transmission and reflection spectroscopy, we further unraveled the near-field absorption and scattering properties of the nanoplate. We performed three-dimensional near-field polarimetry and found that the observed spatial distribution is ascribable to chiral optical fields. We also revealed that the chiral optical field extends beyond the optical near-field, owing to distinct spatial distributions of electric and magnetic fields around the nanoplate. The findings in this report provide a fundamental basis for future plasmonic applications.