Review of plasmonic fiber optic biochemical sensors: improving the limit of detection

Abstract

This paper presents a brief overview of the technologies used to implement surface plasmon resonance (SPR) effects into fiber-optic sensors for chemical and biochemical applications and a survey of results reported over the last ten years. The performance indicators that are relevant for such systems, such as refractometric sensitivity, operating wavelength, and figure of merit (FOM), are discussed and listed in table form. A list of experimental results with reported limits of detection (LOD) for proteins, toxins, viruses, DNA, bacteria, glucose, and various chemicals is also provided for the same time period. Configurations discussed include fiber-optic analogues of the Kretschmann-Raether prism SPR platforms, made from geometry-modified multimode and single-mode optical fibers (unclad, side-polished, tapered, and U-shaped), long period fiber gratings (LPFG), tilted fiber Bragg gratings (TFBG), and specialty fibers (plastic or polymer, microstructured, and photonic crystal fibers). Configurations involving the excitation of surface plasmon polaritons (SPP) on continuous thin metal layers as well as those involving localized SPR (LSPR) phenomena in nanoparticle metal coatings of gold, silver, and other metals at visible and near-infrared wavelengths are described and compared quantitatively.

Graphical Abstract

Artist rendering of light from a tilted fiber Bragg grating probing the cladding surface where  a thin gold film and biofunctional layer are used to detects analytes

Fig. 1

Sketch of the operating principle of the Kretschmann–Raether prism (SPW surface plasmon wave)

Fig. 2

Sketch of the different fiber-optic SPR configurations. I geometry-modified optical fibers: a unclad/etched/tapered fiber, b side-polished/D-shaped fiber, c hetero-core structure, d U-shaped fiber, e arrayed fiber end-face; II fiber gratings: f LPFGs, g TFBGs; III specialty fibers: h PM fiber; i microstructured fiber

Fig. 3

Comparison between the best theoretical SPR response for 50-nm gold on silica in the Kretschmann–Raether configuration (thick blue line) and a measured TFBG-SPR spectrum with the same thickness of gold (thin red line). The arrows indicate the resonance to be followed in each case

Fig. 4

Fiber-optic SPR biosensors fabrication process: I bare fiber components, II fiber surface coating with nano-layer, III bio-sample detection: a direct detection; b sandwich assay; c sandwich assay amplified with Au nanoparticle; d sandwich assay with fluorescence tag. (EW evanescent wave, SPW surface plasmon wave)