Plasmonic Sensor Using a Combination of Grating and Prism Couplings

Surface plasmon-polariton (SPP) waves guided by an interface of a metal and a dielectric material with a combination of grating- and prism-coupled configurations are theoretically investigated for the optical sensing. Change in the refractive index of the partnering dielectric material is sensed by determining the change in the incidence angle and wavelength of excitation of the SPP waves. Two absorptance peaks are observed to determine the sensitivity for a single refractive index in the angular interrogation scheme. One peak corresponds to the prism-coupled configuration and the other peak to the grating-coupled configuration. The double sensing can increase the confidence in the optical measurements. The sensitivity of the proposed sensor is also investigated in the wavelength interrogation scheme.