Hybrid Surface Plasmonic Guided Resonance In A System With Dielectric Covered Metallic Grating

Surface plasmon polaritons(SPPs)are the collective resonant oscillations of conduction electrons especially on the surface of metal material coupled to the electromagnetic field.Twokinds of surface plasmonic modes can be supported by the metal-dielectric surface boundary: the guided surface modes and the guided resonance surface modes.The guided surface plasmonic modes are completely confined on the metal-dielectric surface boundary without any coupling to external radiations.The surface guided resonance modes also have the electromagnetic energy strongly confined on the metal-dielectric surface boundary,which can be excited by grating prism or near-field excitation.Unlike the guided surface plasmonic modes,the guided resonance surface modes can interact with and coupled to external radiations.These surface plasmonic guided modes and guided resonant modes supported by bare metallic gratings have been studied intensively.The optical properties of resonant guided modes in a system with metallic grating covered by dielectric material are investigated by the finite-difference time-domain method and coupled-mode theory.Two kinds of guided resonant modes,the hybrid surface modes supported by the dielectric material and plasmonic surface modes supported by the metallic grating,are mutually coupling and mixing due to anti-crossing.The optical reflective properties of the system are also modeled and investigated by the coupled-mode theory.Conditions for the absorption reduction are also obtained.All the characteristics of the coupling systems are confirmed numerically by the finite-difference time-domain method.This study can be applied to the sensor,the metal grating covered with a layer of media can prevent oxidation,greatly improving the performance and life of the sensor.