Sensitivity enhancement of a conventional gold grating assisted surface plasmon resonance sensor by using a bimetallic configuration

A surface plasmon resonance (SPR)-based refractive index sensor using a silver grating fabricated over the gold film is proposed. The performance of the sensor has been evaluated on the basis of sensitivity, full width half maximum (FWHM), and dip strength of the reflection spectrum. Rigorous coupled wave analysis has been utilized to study the effect of grating parameters on sensing performance. Our systematic analysis exhibits that inappropriate grating parameters may lead to poor performance of the sensor. Sensitivity of the conventional gold grating (grating engraved in gold) assisted SPR sensor is obtained to be 321°/RIU. Further, we have shown that sensitivity and FWHM could be improved by using a bimetallic structure that consists of a silver grating on a thin gold film and thereby increases the quality factor. Sensitivity of the proposed structure is 346°/RIU with a quality factor more than 97.46 RIU−1.