Dual-resonance optical fiber lossy mode resonance refractive index sensor.

In this paper, we propose a dual-channel surface refractive index sensor based on optical fiber lossy mode resonance (LMR). A multilayer transmission matrix model is constructed to simulate and analyze the optical fiber LMR effect based on two semiconductor oxides, SnO2 and TiO2. Through the rational design of structural parameters, we successfully realize the coexistence of mutually independent LMRs on a single fiber, thereby enabling dual-channel sensing. The dual-channel optical fiber LMR sensor was prepared by electrostatically assembling TiO2 nanofilms and SnO2 nanofilms on the sidewall of the optical fiber. The refractive index sensitivity of the dual-channel optical fiber LMR was evaluated via wavelength interrogation, achieving dual-channel refractive index sensing. The refractive index sensitivities are 538.422 nm/RIU and 615.647 nm/RIU in the range of 1.3350 ~ 1.3742. The dual-channel optical fiber LMR refractometer designed in this investigation is a promising platform for the simultaneous detection of multiple protein species and heavy metal ions in biochemical applications.