title: Plasmonic lens focused longitudinal field excitation for tip-enhanced Raman spectroscopy.
abstract: A novel tip-enhanced Raman spectroscopy setup with longitudinal field excitation generated by a plasmonic lens is investigated. A symmetry-breaking structure plasmonic lens that is expected to realize a strong longitudinal electric field focus has been designed to generate suitable excitation for enhancement in a tip antenna. The focusing performance of the plasmonic lens is theoretically simulated by the finite-difference time-domain method and experimentally verified by the detection of optical near-field distribution. A plasmonic lens assisted tip-enhanced Raman spectroscopy setup has been constructed and used to investigate specimens of carbon nanotubes. Tip-enhanced Raman spectra with distinct excitation wavelengths show similar Raman shifts but different intensities. Experimental results presented in this paper demonstrate that the Raman signal is considerably enhanced. It indicates that the novel tip-enhanced Raman spectroscopy configuration is feasible and is a promising technique for tip-enhanced Raman spectroscopy measurements and characterizations.
authors.affiliation: Qian Xuesen Laboratory of Space Technology, China Academy of Space Technology, Youyi Road No. 104, Haidian, Beijing, 100094 China.
authors.forename: Mingqian
authors.initials: M
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, 30 Shuang Qing Lu, Haidian, Beijing, 100084 China.
authors.forename: Jia
authors.initials: J
authors.lastname: Wang
keywords: Longitudinal electric field; Plasmonic lens; Surface plasmon polaritons; Tip-enhanced Raman spectroscopy; Tip-enhancement