Sensitivity enhancement of fiber-optic refractive index sensor based on multimode interference with gold nanoparticles

摘要

In this study, we investigated combinations of fiber-based multimode interference (MMI) sensors with gold nanoparticles (NPs). Gold NPs were synthesized and attached to the MMI sensor region using a silane-coupling agent. Light absorption due to the NPs was confirmed at wavelengths of 560nm and longer, including the telecommunication band (1300-1600 nm). We examined the variation in the interfered wavelengths with changes in the medium surrounding the MMI sensor, both with and without NPs. The interfered wavelengths were redshifted when the refractive index (RI) increased, and the shift with NPs was almost twice as large as the shift without NPs. We determined the sensitivity of the MMI sensor with NPs to be approximately 218.28 nm/RIU (refractive index unit) in a refractive index range from 1.31535 to 1.35199. (C) 2015 The Japan Society of Applied Physics