Ultrahigh-sensitivity refractive-index sensor based on gold-coated side-polished photonic crystal fiber

The coupling characteristics of a gold-coated side-polished photonic crystal fiber based on surface plasmon resonance are simulated. The resonant points undergo a blue-shift unexpectedly when the refractive indices of the analytes range from 1.32 to 1.50, and a negative sensitivity is observed in the sensing scheme. The wavelength and amplitude are investigated to characterize the device. The highest negative wavelength sensitivity is −40,400 nm/RIU with a resolution of 2.48 × 10−6 RIU, and the corresponding amplitude sensitivity is as high as −1,246.47 RIU−1 with a resolution of 8.02 × 10−6 RIU. The sensor shows excellent performance that is comparable to previous reports.