Performance parameters of a Ag-coated evanescent field optical fiber sensor for temperature measurement via surface plasmon resonance

The performance parameters of a type of sensing device for temperature measurement are determined experimentally and theoretically using a technique of excitation of surface plasmon resonances in optical fibers. The developed device consists of a tapered optical fiber coated with silver nanoparticles (AgNPs) that were obtained using the green synthesis technique. For the verification of the experimental results, the transference matrix model, the Drude model and the theory of surface plasmon resonance in the Kretschmann configuration was used. During the investigation it is verified that the transmittance measured as a response signal of the optical fiber is in accordance with the theoretical results obtained from the mathematical modeling. To determine the performance parameters of the device developed for temperature measurement, the sensitivity S and the figure of merit FOM of the device were determined from the rate of change of the plasmon resonance wavelength shift as a function of the temperature gradients and transmission spectra at the output of the tapered optical fiber for different temperature values, observing a red shift of the plasmonic resonance wavelength with decreasing temperature. For the case of FOM, this was determined indirectly using S and Full Width at Half Maximum FWHM. Experimental results reveal that the developed devices exhibit sensitivities in the order of -0.18 nm/°C to -0.52 nm/°C with excellent reproducibility, while the FOM is in the order of 1.7 × 10^{− 2} °C^{− 1} to 2.4 × 10^{− 2} °C^{− 1}. Theoretical and experimental results reveal that the sensitivity of the sensor presents a dependence on the geometrical parameters of the device, the nature of the coating and the surface of the device.