Sensitivity enhancement of a surface plasmon resonance based fiber optic sensor using ZnO thin film: a theoretical study

•An SPR based fiber optic sensor with bi layers of metal–ZnO is theoretically studied.•Three metals; Au, Ag and Cu have been used in the study.•Top ZnO layer protects metallic layer from oxidation and enhances the sensitivity.•Increase in thickness of Au/Ag/Cu layer increases the sensitivity.•Sensitivity also increases with increase in ZnO layer thickness.

A surface plasmon resonance (SPR) based fiber optic sensor with bi layers of metal–ZnO is proposed and theoretically studied. Three metals: gold (Au), silver (Ag) and copper (Cu) have been exercised in the study. The top ZnO layer is shown to protect the metallic layer from oxidation and to enhance the sensitivity of the SPR sensor. Besides, increase in thickness of Au/Ag/Cu layer increases the sensitivity of SPR sensor for all thicknesses of ZnO layers. For a fixed thickness of ZnO layer, the sensitivity of sensor is larger for Au layer than that of Ag/Cu layer. Sensitivity also increases with increase in ZnO layer thickness for all thicknesses of Au/Ag/Cu layers. The SPR sensor based on bi layers of 40 nm Au–15 nm ZnO demonstrates the maximum sensitivity of 3161 nm/RIU.