Coupling of surface plasmons between two silver films in a Ag/SiO2/Ag plasmonic thermal emitter with grating structure

The reflection and emission spectra of Ag/SiO2/Ag trilayer plasmonic thermal emitters with different SiO2 thicknesses are investigated. The top Ag film is perforated with periodic slits. It is found that the coupling of surface plasmons at the top and bottom Ag/SiO2 interface results in the redshift in thermal emission peaks. In this Ag/SiO2/Ag plasmonic thermal emitter, the electromagnetic field exhibits either Fabry-Perot resonance or propagating surface plasmons depending on the thickness of SiO2 layer. By varying the thickness of SiO2 layer, transition from localized to grating-coupled propagating surface plasmon modes is observed.