Abstract
We investigated the near-field response in silver nanoparticle aggregates to the excitation of circular polarized light. In a right-angle trimer system, the local field intensity excited by right-hand circularly polarized light is almost one thousand times larger than the left-hand case. By analyzing the polarization and phase of the local field in plasmonic hotspots, we found this local circular dichroism is originated from the near-field interference excited by orthogonal polarized incident lights. The local circular dichroism can be tuned by the rotation of the third particle, the interparticle distance, and the dielectric environment. This phenomenon could also widely exist in more complicated nanoaggregates. These findings would benefit for resolving light handedness, and enhancing circular dichroism and optical activity.
Highlights
Giant local circular dichroism within an asymmetric plasmonic nanoparticle trimer Hancong Wang[1,2], Zhipeng Li1,2, Han Zhang[1,3], Peijie Wang2 & Shuangchun Wen[1]
By analyzing the polarization and phase of the local field in plasmonic hotspots, we found this local circular dichroism is originated from the near-field interference excited by orthogonal polarized incident lights
Chiroptical effects are typically characterized by small differences of extinction coefficients or refractive indexes in the interaction of left-hand circularly polarized light (LCP) and right-hand circularly polarized light (RCP) with chiral molecules, leading to circular dichroism (CD) or optical activity (OA)[1]
Summary
Giant local circular dichroism within an asymmetric plasmonic nanoparticle trimer Hancong Wang[1,2], Zhipeng Li1,2, Han Zhang[1,3], Peijie Wang2 & Shuangchun Wen[1]. We investigated the near-field response in silver nanoparticle aggregates to the excitation of circular polarized light. New chiral center might generate for different sorption sites in aggregates, which makes it challenging to obtain the stability and repeatability of SEROA It was found even for an achiral molecule in a planar nanoparticle trimer, Raman scattering of the molecule can carry a considerable degree of circular polarization, that is, scattered circular polarization Raman optical activity (SCP ROA)[22,23]. The origin of this plasmonic ROA in the molecule-aggregates system is the nanoantenna effect of asymmetric particles excited by the Raman emission of the molecule[24]. This study could provide a more flexible way to design plasmonic nanostructures with strong CD or ROA response for various applications such as polarization sensitive devices[3,8] and plasmonic sensors[36,37]
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