Performance Analysis of Bimetallic Layer With Zinc Oxide for SPR-Based Fiber Optic Sensor

We present an efficient fiber optic SPR sensor consisting of bimetallic layers of silver (Ag) and gold (Au) in coordination with zinc oxide (ZnO) for refractive-index sensing in spectral mode. The performance of the sensor is explored in terms of electric field intensity, sensitivity, and the figure of merit theoretically as well as experimentally. Four kinds of sensors with layers of Ag/ZnO, Au/ZnO, Au/Ag/ZnO, and Ag/Au/ZnO over an unclad core of the fiber are studied. For simulation, two-dimensional multilayer matrix method along with geometrical optics is used. It is found that the sensor having layers of Ag/Au/ZnO with optimized thicknesses possesses maximum electric field intensity at the interface, large shift in the resonance wavelength, sharp SPR dip, and high value of the figure of merit. In addition, the additional layers of Au and ZnO can also be used for the tuning of resonance wavelength in the visible region of the electromagnetic spectrum and for the protection of Ag layer from oxidation and; hence, can improve the durability of the sensor. Further, ZnO layer can also be used to sense some of the gases.