Highly sensitive plasmonics temperature sensor based on photonic crystal fiber with a liquid core

An ultra-high sensitivity temperature sensor based on photonic crystal fiber (PCF) is proposed and demonstrated. The central hole and the two holes coated with nanoscale gold film are assumed to be filled with temperature sensitive liquid. The refractive index of the liquid decreases as the temperature increases with the temperature sensitive coefficient of -3.9 × 10−4/oC. The liquid of the central hole with high refractive index supports liquid-core mode. As the phase matching condition is satisfied, the liquid-core mode couples to the surface plasmon polariton mode and presents energy loss. The influences of the PCF structural parameters and the thickness of the gold film on the resonance wavelength, loss value and sensitivity are studied. The resonance wavelength and confinement loss increase as the temperature increases. The average sensitivity can reach to 9.89 nm/oC (∼25359 nm/RIU) as the temperature changes from 35 °C to 45 °C and the R-square is 0.99992. By replacing the liquid core by silica core, we find the sensitivity is very low. We also compare the PCF without liquid in the holes coated with gold film by our structure and find that the sensitivity is nearly unchanged and the confinement loss is slightly decreased.