An ultraviolet sensor based on surface plasmon resonance in no-core optical fiber deposited by Ag and ZnO film

Abstract

A new ultraviolet (UV) optical fiber sensor based on surface plasmon resonance (SPR) is suggested in this research, which is fabricated by splicing a segment of no-core optical fiber (NCF) between two multimode optical fibers (MMFs). An Ag film and a ZnO film are successively deposited upon the surface of the NCF by magnetron sputtering, and the UV detection function is accomplished by utilizing SPR's sensitivity to ambient refractive index (RI) and ZnO RI's sensitivity to the UV irradiance. Due to the hydrophilic properties of ZnO, the sensor is encapsulated in absolute ethanol to produce stable SPR and isolate water molecules. The effects of film thickness (Ag and ZnO) and UV irradiance on sensor performance are discussed in detail. It is discovered that the UV sensitivity of the sensor increased with the ZnO thickness. At the deposition of a 10 nm thick ZnO film, the sensitivity can reach -1.462 nm / (mW/cm2), which is 6 times that of 2 nm thick film. The exploratory combination of SPR and UV sensitive materials tremendously simplifies UV detection technology, making the sensor highly reproducible and UV detection more efficient in the fields of environmental monitoring, food hygiene, and medical health.