Boosting the Figure Of Merit of LSPR-based refractive index sensing by phase-sensitive measurements

TL;DR

This paper demonstrates that phase-sensitive measurements of localized surface plasmon resonances significantly improve the figure of merit in refractive index sensing by reducing linewidths and capturing intrinsic phase transitions.

Contribution

It introduces phase-sensitive measurement techniques for LSPR sensors, achieving substantially higher FOMs compared to traditional intensity-based methods.

Findings

Linewidths are nearly ten times smaller with phase measurements.

FOM values up to 8.3 and 16.5 for different nanoparticle systems.

Phase information enhances sensitivity and resolution in plasmonic sensing.

Abstract

Localized surface plasmon resonances possess very interesting properties for a wide variety of sensing applications. In many of the existing applications only the intensity of the reflected or transmitted signals is taken into account, while the phase information is ignored. At the center frequency of a (localized) surface plasmon resonance, the electron cloud makes the transition between in- and out-of-phase oscillation with respect to the incident wave. Here we show that this information can experimentally be extracted by performing phase-sensitive measurements, which result in linewidths that are almost one order of magnitude smaller than those for intensity based measurements. As this phase transition is an intrinsic property of a plasmon resonance, this opens up many possibilities for boosting the figure of merit (FOM) of refractive index sensing by taking into account the phase of the plasmon resonance. We experimentally investigated this for two model systems: randomly distributed gold nanodisks and gold nanorings on top of a continuous gold layer and a dielectric spacer and observed FOM values up to 8.3 and 16.5 for the respective nanoparticles.