One step method to attach gold nanoparticles onto the surface of an optical fiber used for refractive index sensing

•A novel, simple and fast method was developed to detect the refraction index.•An optical fiber surface was modified with gold nanoparticles.•A refractive index sensor based on localized surface plasmon resonance was added.•This sensor has a sensitivity of 765 nm/RIU and a resolution of ∼1 × 10−4 RIU.•A refractive index range of 1.333–1.365 was obtained with this sensor.

Localized surface plasmon resonance (LSPR) has recently emerged as an efficient and powerful tool for bio-photonic applications due to its high sensitivity to refractive index changes. One technique to excite LSP is by the interaction of the evanescent wave of the light guided by an optical fiber with metallic nanoparticles deposited over the surface of the fiber. This paper proposes a novel, simple, and fast method to attach gold nanoparticles to the optical fiber surface, which can be used to construct highly sensitive refractive index sensors based on localized surface plasmon resonance. A hetero-core structured fiber, composed by a small section of single-mode fiber inserted in a multimode fiber, was coated with nanoparticles using the method proposed here. A sensor sensitivity and resolution of 765 nm/RIU and ∼1 × 10−4 RIU, respectively, were estimated over a refractive index range of 1.333–1.365. This coating method is appealing to construct optical fiber refractive index sensors since it is very simple and low cost.

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