Lossy mode resonance fiber-optic sensor based on ZnO particles fabricated by chemical bath deposition

We present a lossy mode resonance (LMR) sensor fabricated by chemical bath deposition (CBD) using a U-shaped optical fiber with an exposed core. The ZnO particles that generate LMR were prepared by a very costly method in three steps via permanganate activation and the deposition of ZnO on the fiber core using CBD. The process of deposition was monitored in real time through the optical fiber, and a clear absorption spectrum with an LMR peak was obtained. The surface of the sensor with absorbance reaching 1.0 was covered with nano- to submicron particles of ZnO. The refractive index (RI) sensitivity of the sensor was measured using sucrose solution and was found to increase as the amounts of ZnO on the sensor increased, reaching 23 Abs/RI unit (RIU). The RI resolutions of the sensors with absorbance reaching 0.40, 0.65, and 1.0 during CBD were determined as ΔRI = 0.000060, 0.00017, and 0.00018, respectively, with a 99.7% confidence interval for the RI. Pretreatment during CBD was found to dramatically affect the fabrication of LMR sensors owing to their size and occupancy of deposited ZnO particles, the effects of which can be observed in real time using fiber optics.