Analytical Study on Sensitivity Enhancement of an Angularly Interrogated LRSP Sensor

An analytical study of the sensitivity enhancement of an angularly interrogated long range surface plasmon (LRSP) sensor, with a closed symmetric transducer structure consisting of a prism, Teflon and gold layers, is presented. The effects of the sensor design parameters, such as wavelength and the thicknesses of the gold and Teflon layers, on the angular (S-theta) and intrinsic (IS theta) sensitivities are studied for cover refractive indices varying from 1.33 to 1.37. The angular and intrinsic sensitivity calculations for the transverse mode TM mode are conducted for wavelengths ranging from 500 nm to 1000 nm. The best averaged angular and intrinsic sensitivity values are 246 degRIU(-1) and 251 RIU-1 at 1000 nm, respectively; however, these values were achieved with different thickness combinations of the gold and Teflon layers supported by a BK7 triangular prism. The LRSP sensor's intrinsic sensitivity is better than the results calculated for prism-Teflon-gold LRSP configurations published in the literature. Although it is feasible to optimize the sensor's design parameters for high precision measurements of the bulk refractive index, the sensitivity of the LRSP on a very thin layer of the molecular formation must be investigated.