posted on 2021-09-28, 20:12authored byTomoya Oshikiri, Quan Sun, Hiroki Yamada, Shuai Zu, Keiji Sasaki, Hiroaki Misawa
The optical near
field (NF) induced by circularly polarized light
(CPL) is a hot scientific topic. We observed a chiral NF intensity
distribution on a series of achiral gold nanorectangular structures
(Au-NRs) under CPL irradiation by using multiphoton photoemission
electron microscopy (MP-PEEM). Additionally, the differential NF spectra
under left and right CPL irradiation, which represent the asymmetry
of the NF intensity distribution, were investigated. We propose an
interpretation that the chiral NF intensity distribution on an achiral
metallic nanostructure is extrinsically generated by the interference
between two plasmonic modes by combining state-of-the-art MP-PEEM
techniques and the classical oscillator model. Our interpretation
well explains both the experimental and simulation results. Furthermore,
the intensity of the NF and its phase angle of each mode under linearly
polarized light irradiation were revealed to be critical factors for
the generation of extrinsic chirality in the NF intensity distribution.