The role of Ta2O5 thin film on a plasmonic refractive index sensor based on photonic crystal fiber

In this paper, a highly sensitive plasmonic refractive index (RI) sensor based on photonic crystal fiber (PCF) is proposed. Silver (Ag) is used as plasmonic material and tantalum pentoxide (Ta2O5), high RI material, is used as an overlayer over the silver thin film. The sensor performance is realized using surface plasmon resonance (SPR) phenomenon. The effect of tantalum pentoxide overlayer thickness on sensing parameter as well as on sensitivity is analyzed in detail using finite element method (FEM). The detailed study shows an interesting property that the increasing Ta2O5 layer thickness can tune the operating analyte RI from high RI region to low RI region i.e. towards the aqueous medium. The structural parameters of the proposed sensor are being optimized and its sensitivity is realized using wavelength interrogation technique. A maximum sensitivity of 50000 nm/RIU is reported. This study, no doubt, provides a new direction of designing RI sensor that could tune RI range by varying the only the Ta2O5 layer thickness to the desired operating analyte region. Besides, the simple design feasibility, low fabrication cost and portable nature of the proposed sensor make it suitable for industrial and chemical sensing applications.