Self-Assembly of Plasmonic Nanoantenna-Waveguide Structures for Subdiffractional Chiral Sensing
Journal article
Abstract
Spin-momentum locking is a peculiar effect in the near-field of guided optical or plasmonic modes. It can be utilized to map the spinning or handedness of electromagnetic fields onto the propagation direction. This motivates a method to probe the circular dichroism of an illuminated chiral object. In this work, we demonstrate local, subdiffraction limited chiral coupling of light and propagating surface plasmon polaritons in a self-assembled system of a gold nanoantenna and a silver nanowire. A thin silica shell around the nanowire provides precise distance control and also serves as a host for fluorescent molecules, which indicate the direction of plasmon propagation. We characterize our nanoantenna{\textendash}nanowire systems comprehensively through correlated electron microscopy, energy-dispersive X-ray spectroscopy, dark-field, and fluorescence imaging. Three-dimensional numerical simulations support the experimental findings. Besides our measurement of far-field polarization, we estimate sensing capabilities and derive not only a sensitivity of 1 mdeg for the ellipticity of the light field, but also find 103 deg cm2/dmol for the circular dichroism of an analyte locally introduced in the hot spot of the antenna{\textendash}wire system. Thorough modeling of a prototypical design predicts on-chip sensing of chiral analytes. This introduces our system as an ultracompact sensor for chiral response far below the diffraction limit.
Publication Details
Author list: Rothe M, Zhao Y, Müller J, Kewes G, Koch CT, Lu Y, Benson O
Journal: ACS Nano
Publication year: 2020
Volume number: 15
Issue number: 1
Publisher: American Chemical Society
ISSN: 1936-0851
eISSN: 1936-086X
