title: Mapping plasmonic near-field profiles and interferences by surface-enhanced Raman scattering.
abstract: Mapping near-field profiles and dynamics of surface plasmon polaritons is crucial for understanding their fundamental optical properties and designing miniaturized photonic devices. This requires a spatial resolution on the sub-wavelength scale because the effective polariton wavelength is shorter than free-space excitation wavelengths. Here by combining total internal reflection excitation with surface-enhanced Raman scattering imaging, we mapped at the sub-wavelength scale the spatial distribution of the dominant perpendicular component of surface plasmon fields in a metal nanoparticle-film system through spectrally selective and polarization-resolved excitation of the vertical gap mode. The lateral field-extension at the junction, which is determined by the gap-mode volume, is small enough to distinguish a spot size ~0.355λ0 generated by a focused radially polarized beam with high reproducibility. The same excitation and imaging schemes are also used to trace near-field nano-focusing and interferences of surface plasmon polaritons created by a variety of plasmon lenses.
authors.affiliation: School of Electrical & Electronic Engineering, Nanyang Technological University, Nanyang Avenue 639798, Singapore.
authors.forename: Luping
authors.initials: L
authors.lastname: Du
authors.forename: Dang Yuan
authors.initials: DY
authors.lastname: Lei
authors.forename: Guanghui
authors.initials: G
authors.lastname: Yuan
authors.forename: Hui
authors.initials: H
authors.lastname: Fang
authors.forename: Xi
authors.initials: X
authors.lastname: Zhang
authors.forename: Qian
authors.initials: Q
authors.lastname: Wang
authors.forename: Dingyuan
authors.initials: D
authors.lastname: Tang
authors.forename: Changjun
authors.initials: C
authors.lastname: Min
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Maier
authors.forename: Xiaocong
authors.initials: X
authors.lastname: Yuan