title: Plasmonic rainbow rings induced by white radial polarization.
abstract: This Letter presents a scheme to embed both angular/spectral surface plasmon resonance (SPR) in a unique far-field rainbow feature by tightly focusing (effective NA=1.45) a polychromatic radially polarized beam on an Au (20 nm)/SiO2 (500 nm)/Au (20 nm) sandwich structure. Without the need for angular or spectral scanning, the virtual spectral probe snapshots a wide operation range (n=1-1.42; λ=400-700 nm) of SPR excitation in a locally nanosized region. Combined with the high-speed spectral analysis, a proof-of-concept scenario was given by monitoring the NaCl liquid concentration change in real time. The proposed scheme will certainly has a promising impact on the development of objective-based SPR sensor and biometric studies due to its rapidity and versatility.
authors.affiliation: Department of Photonics and Institute of Electro-optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan.
authors.forename: Tzu-Hsiang
authors.initials: TH
authors.lastname: Lan
authors.forename: Yi-Kuan
authors.initials: YK
authors.lastname: Chung
authors.forename: Jie-En
authors.initials: JE
authors.lastname: Li
authors.forename: Chung-Hao
authors.initials: CH
authors.lastname: Tien