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; lambda = 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. (C) 2012 Optical Society of America