Selective absorption and emission from a stacked subwavelength and Bragg grating backed with metal film

The ultranarrow-band spectrum selective absorption and emission effect of stacked grating structures is studied. Two TE polarization absorbers/emitters are designed and investigated. One is composed of a metallic grating backed with a Bragg grating. The other one consists of a metallic grating and a reduced Bragg grating backed with a metallic film. Both exhibit near-unity absorption and emission at the resonant wavelengths but with ultranarrow spectrum and antenna-like response. The electric field distributions at resonant wavelengths are presented to provide a satisfactory qualitative understanding of such absorption/emission behavior. The designed absorbers/emitters have application in various scientific and technological fields and it is also believed the conclusions may be helpful for the design of a ultranarrow absorber/emitter.