Cross-Comparison of Surface Plasmon Resonance-Based Optical Fiber Sensors With Different Coating Structures

Abstract

In this paper, optical fiber sensors, based on both surface plasmon resonance (SPR) and localized SPR (LSPR) approaches, have been successfully developed and cross-compared. The SPR sensor has been constructed by coating a thin layer of gold film on a piece of an optical fiber with the cladding having first been removed. Several LSPR sensors, however, have been configured in a slightly different way through coating several unclad fibers, each with a thin layer of gold-nanorods (GNRs) with a different aspect ratio. Subsequently, both SPR and LSPR sensors are exposed to solutions with different refractive index and their corresponding plasmon resonance wavelength shifts have been recorded and cross-compared. The experimental results obtained confirm that the SPR sensor has demonstrated a much higher sensitivity than that of any of the LSPR sensors, irrespective of the variation of the aspect ratio of GNRs coated. The LSPR sensors, however, have demonstrated a much better linearity compared to that of the SPR sensor.