Effects of gold film thickness on spectrum profile and sensitivity of a multimode-optical-fiber SPR sensor

For a multimode-optical-fiber surface plasmon resonance (SPR) sensor with a gold film supporting surface plasmon waves (SPWs), we have investigated the effects of gold thickness on sensor performance experimentally to find the optimal thickness when a white-light source is used. It is found that the sensor with a thickness of around 65 nm enables most precise measurement of a resonance wavelength and gives relatively high sensitivity, which is 1557 nm/RIU in the refractive index range of 1.333–1.3469. Also, we have confirmed that a simulation model based on meridional rays cannot explain the minimum reflectance of SPR spectra for values below 0.5.