Effect of Noble Metal Thin Film Thicknesses on Surface Plasmon Resonance (SPR) Signal Amplification

This work is carried out to study the effect of noble metal thicknesses, namely gold and silver on the SPR characteristics for smart food packaging technology applications. A Kretschmann prism coupling was introduced to excite surface plasmon polaritons (SPP). The optical refractive indices values of gold and silver were set as Rgold=0.1759+3.4104i and Rsilver=0.0585+4.2665i respectively. The thicknesses of noble metal thin films were varied between t=25nm and 95nm with the increment of 10nm for each reading. SPR signal analyses were performed by studying the characteristics of SPR peaks such as Q-factor and FWHM. Both analyses demonstrated an outstanding optical properties of silver at t=55nm in comparison with gold due to its low FWHM and high Q-factor values which proves its ability to generate excellent amount of SPP. The employment of silver witnessed the enhancement of Q-factor value up to 7.09% and the decrement of FWHM about 76.58%, relatively with gold. The introduction of silver able to convert 87.20% SPP, whilst the usage of gold only capable to excite 81.4% SPP. In conclusion, application of silver noble metal at t=55nm able to generate maximum SPR. This excellent criterion placed silver as a spectacular candidate in the development of low cost and high sensitive SPR sensor for food quality assessment applications.