Optimization of plasmonic sensors based on sinusoidal and rectangular gratings

Abstract

Surface plasmon resonance (SPR) sensors based on metal gratings have received much attention for designing compact and portable biosensors. In this paper, we systematically optimize SPR sensors based on sinusoidal and rectangular gratings to improve the performance of this kind of sensors. A parameter (FOM*) is defined to evaluate the sensor performance, which combines the sensitivity, FWHM, and depth of the SPR absorption peak. We find that grating period of 560 nm is suitable to locate the SPR peaks in the optimal response range of silicon detectors and ensures high sensitivity. For sinusoidal gratings, the highest FOM* of 99.25 is achieved at grating depth of 15 nm. The highest FOM* for rectangular grating with continuous metal film is 123.70 when grating depth and duty cycle are 12 nm and 0.3, respectively. With grating depth of 24 nm and duty cycle of 0.8, the highest FOM* of 25.23 is obtained for rectangular grating with discontinuous metal film. These optimization results can be directly used to improve the detection limit of compact SPR sensors.