Low Dimensional Nanostructure-Assisted Long-Range Surface Plasmon Resonance Sensors With High Figure of Merit.

Long-range surface plasmon resonance (LRSPR) sensors have been extensively studied by virtue of their extremely narrow full width at half maxima (FWHM) characteristics, but their low sensitivity remains an important factor limiting the figure of merit (FOM), making the sensors have difficulties in detecting small refractive index changes accurately. To address this problem, this paper proposes and demonstrates a low dimensional nanostructure (Au nanospheres, WS2) assisted LRSPR sensor to achieve an effective enhancement of the sensor interfaced electric field and thus improve the sensitivity. The performance parameters of the two sensors are compared with the LRSPR sensor by finite element method analysis, and the results showed that the assistance of the low dimensional nanostructure has a positive effect on the sensor. The first refractive index sensing experiment of the WS2-assisted LRSPR sensor was realized with a 25.47% increase in sensitivity and a 7.13% increase in FOM simultaneously, and the Au nanospheres-assisted LRSPR sensor with a 29.23% increase in sensitivity and a 15.95% increase in FOM simultaneously. The introduction of low dimensional nanostructures provides a flexible and effective means of sensitization for LRSPR sensors, making the plasmon resonance sensors combine high sensitivity, narrow FWHM and high FOM, which have promising applications in biochemical sensing.

Plasmonic crescent nanoarray-based surface lattice resonance sensor with a high figure of merit.

Due to the natural accumulation of radiation losses arising from the localization and random arrangement of nanoparticles, the figure of merit (FOM) of localized surface plasmon resonance (LSPR) sensors is usually very low (the value is usually less than 5 RIU-1). However, radiation losses of individual particles will be offset by adjusting the phase of the scattered field which is dependent on the structure parameters of arrays. Based on this, a two-dimensional periodic crescent nanoarray-based surface lattice resonance (SLR) sensor with a high FOM is proposed in this work. Some significant results have been obtained by mode field analysis and adjustment of structural parameters. On the one hand, the line-shape of the SLR spectrum is divided into a Fano-like line and a separate line. And the former usually has an FOM of 101 magnitude while the latter has an FOM of 103 magnitude. On the other hand, the relative size of the excitation wavelengths between SLR and LSPR is also vital. The FOM is higher but resonance depth decreases faster when the relative size increases. In this work, a full width at half-maximum (FWHM) of less than 0.5 nm and FOM of more than 1000 RIU-1 (the quality factor is more than 3000) are achieved by the proposed crescent nanoarrays. In addition, this structure demonstrates that plasmonic nanoarray-based SLR has enormous potential in trace substance detection.