Demonstration of an ultrasensitive refractive-index plasmonic sensor by enabling its quadrupole resonance in phase interrogation

Abstract

We present an ultrasensitive plasmonic sensing system by introducing a nanostructured X-shaped plasmonic sensor (XPS) and measuring its localized optical properties in phase interrogation. Our tailored XPS exhibits two major resonant modes of a low-order dipole and a high-order quadrupole, between which the quadrupole resonance allows an ultrahigh sensitivity, due to its higher quality factor. Furthermore, we design an in-house common-path phase-interrogation system, in contrast to conventional wavelength-interrogation methods, to achieve greater sensing capability. The experimental measurement shows that the sensing resolution of the XPS reaches 1.15×10(-6) RIU, not only two orders of magnitude greater than the result of the controlled extinction measurement (i.e., 9.90×10(-5) RIU), but also superior than current reported plasmonic sensors.

Detuned Plasmonic Bragg Grating Sensor Based on a Defect Metal-Insulator-Metal Waveguide

“…In addition, an ultra-compact loop-stub biosensor and structure of metal nanoslit arrays have been proposed [ 18 , 19 ]. In order to improve the sensing performance straightforwardly, Zhengqi Liu presents a sensor based on the suspended plasmonic crystal [ 20 ], a nanostructured X-shaped plasmonic sensor has been designed for investigation phase interrogation [ 21 ]. A mechanical sensor has been presented to achieve trapping and releasing of light and high-speed rainbow trapping and releasing [ 22 , 23 ].…”

Quantum Mechanical Identification of Quadrupolar Plasmonic Excited States in Silver Nanorods

“…Plasmonic noble metal nanostructures have been of broad interest in recent years, since their unique optical properties can enhance important properties of nearby molecules such as absorption, , fluorescence, , and Raman spectroscopy. − In a classical electrodynamics picture, the plasmonic states involve coherent oscillation of all of the conduction band electrons within the nanostructure. − Although the majority of interest has been in the dipolar plasmon resonances where the full electron cloud responds in phase with the electric field of light (Figure ), higher-order plasmon resonances such as quadrupoles have long been known to occur and in the past several years have gained attention for various applications. − The quadrupolar modes are typically optically dark in small nanostructures, but can be excited via near-field radiation − or, in larger nanostructures where the retardation of light across the nanostructure is significant, by far-field radiation. ,− Electrodynamics simulations ,, and experimental studies ,, consistently show that the quadrupolar modes are higher in energy and have much narrower absorption peaks than the corresponding dipolar modes. In rod-shaped nanostructures, electron energy loss spectroscopy (EELS) experiments have revealed the spatial distribution of the longitudinal plasmon modes with various multipolar character.…”

“…Perhaps counterintuitively, the quadrupolar modes can in some cases provide more enhancement of the spectroscopic or chemical properties of nearby molecules or semiconductor particles than the dipolar modes. In particular, the quadrupolar modes of various nanostructures have been shown to yield larger figures of merit for refractive index sensing, ,,, stronger enhancement of surface-enhanced Raman spectroscopy, ,, and may have the dominant contribution to the emission enhancement of nearby semiconductor particles. , Thus, an improved understanding of the chemical nature and structural dependence of the quadrupolar plasmon modes may contribute to the design of nanostructures for many applications.…”

Alternating Nanolayers of Dielectric MgF2 and Metallic Ag as Hyperbolic Metamaterials: Probing Surface States and Optical Topological Phase Transition and Implications for Sensing Applications

“…Illustration of the optical setup of our homemade wavelength and angle interrogation system . The lens set is utilized to collimate the white light source.…”