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The vector beam assisted “hot‐spot” optimization in tip‐enhanced Raman spectroscopy
Author(s) -
Zhou Rong,
Chen Li,
Kong Ting,
Chen Huan,
Zhang Zhenglong,
Shen Hao,
Zheng Hairong
Publication year - 2021
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.6202
Subject(s) - raman spectroscopy , plasmon , optics , surface enhanced raman spectroscopy , materials science , electric field , polarization (electrochemistry) , spectroscopy , optoelectronics , beam (structure) , excited state , chemistry , raman scattering , physics , atomic physics , quantum mechanics
Tip‐enhanced Raman spectroscopy has already promised extremely high plasmonic enhancement due to the successful optical confinement inside the nanocavity or sub‐nanocavity between the tip apex and substrate. Yet the dipole‐like charge oscillation enabled the gap enhancement, and hence, only the vertical polarization component could match and contribute to the overall efficiency. To avoid the noise and pursuit the mode purity, we chose the vector beam to form a tightly focused vertical electric field to generate such a “hot‐spot.” For the bottom illuminated method, taking the opaqueness and absorption characteristics of the beam by the metal substrate into consideration, the substrate thickness becomes the critical factor concerning gap plasmons coupling effect and incident light transmittance. Here, the spatial resolution lines of the vector beam excited from the bottom were compared with that of side method excited by linearly polarized beam, which shows that the vector beam presents greater symmetric characteristics. In addition to better elucidating the mechanism of tip‐enhanced Raman spectroscopy, our results can be applied to a rational reference and guidance for later experiments.