High-performance bimetallic film surface plasmon resonance sensor based on film thickness optimization

The performance of a surface plasmon resonance (SPR) sensor with silver-gold bimetallic film based on angular interrogation was presented. To achieve minimal reflectance at resonance angle, the thicknesses of silver and gold layers of the bimetallic sensor were optimized at first. Then, the sensitivity and full-width-half-maximum (FWHM) of SPR sensors with optimum silver-gold thicknesses were investigated. With the increasing of the thickness of silver layer in bimetallic film, both the sensitivity and FWHM of the SPR sensor decreases, which indicates that the bimetallic sensor can obtain higher sensitivity than the SPR sensor with single silver layer, and smaller FWHM than the one with single gold layer. In addition, by analyzing the electric field inside the bimetallic SPR sensor, we studied the underlying physics of the improvement of the bimetallic sensor performance.