Sensitivity enhanced D-type large-core fiber SPR sensor based on Gold nanoparticle/Au film co-modification

Abstract

A D-type large core optical fiber sensor with high sensitivity and good stability based on the coupling of gold nanoparticles and Au film was proposed and demonstrated by simulation and experiments. The proposed sensor is numerically simulated based on the finite element method. The simulation shows that the electric field intensity of the gap coupling between gold nanoparticles and Au film is 4–5 times higher than that of Au film, and the electric field intensity on the surface of gold nanoparticles is twice as strong as that on the surface of Au films. The electric field coupling effect between the Au film surface plasmon resonance (SPR) and the gold nanoparticle localized surface plasmon resonance (LSPR) can improve the refractive index sensitivity of the sensor. Experimental results show that the refractive index sensitivity of D-type optical fiber/Au film/gold nanoparticles sensor reaches 3074 nm/refraction index unit (RIU), which is 1.4 times that of D-type optical fiber/Au film sensor. SPR–LSPR coupling effect is a good method to improve the sensing performance of optical fiber sensors, especially for detecting the refractive index changes of surrounding media. Compared with existing similar biosensors, the designed biosensor has higher sensitivity and the sensor proposed in this paper has great application prospects in the field of biological detection.