  The selection of a suitable plasmonic material is extremely crucial for
achieving high-performance photonic crystal fiber-based surface plasmon
resonance (PCF-SPR) sensors. However, most numerical investigations to date are
limited to PCF-SPR sensors with conventional circularly coated plasmonic metals
due to their availability and rigid properties. In this work, a single-core
arc-shaped photonic crystal fiber is designed and studied with sensing
ingredients coated outside the fiber. The simulation and numerical analyses
were performed using the full-vector finite element method (FV-FEM) to examine
the effects of using gold as active metal and also the deposition of $Ta_2 O_5$
on gold. The results show that the arc-shaped sensor with gold film can obtain
the maximum wavelength interrogation sensitivity (WIS) of 9500 nm/RIU within
the refractive index (RI) range of 1.25 to 1.39 while the maximum amplitude
interrogation sensitivity (AIS) is reached 579.26 $RIU^{-1}$ at 1.39 and
resolution is found to be 1.05 x ${10^{-5}}$. However, depositing $Ta_2 O_5$ on
the gold gives an improved maximum WIS and AIS of 22000 nm/RIU, and 1209.21
$RIU^{-1}$, respectively. With the coating of $Ta_2 O_5$, the resolution
improves to 4.55 x ${10^{-6}}$ making the proposed sensor design undoubtedly
effective in detecting different biological samples with a wide range of RI.
