Résumé
A metamaterial perfect absorber based on layered, doped and undoped semiconductors is experimentally and theoretically investigated. Design rules are given to control the multispectral, narrow, strong absorption features (>98% absorption) in the mid-IR spectrum. The proposed sub-wavelength grating structures support localized surface plasmons and photonic resonances associated to the quarter wavelength optical thickness of the undoped spacer layer. The resonances hybridize depending on the geometric setup of the metamaterial and the material properties of the heavily doped semiconductor. The angular response of the resonances is studied to determine the acceptance angle. While the absorption is best at near-normal incidence, the spectral position of the absorption bands is weakly dependent on the angular incidence up to angles of 45 degrees. Complementary to the polarization-dependent grating design of the metamaterial, an alternative based on a crossed grating nanopattern is also investigated for polarization insensitivity. Furthermore, it is demonstrated that the metamaterial perfect absorber provides a tailored thermal emission spectrum. Based on the heavily doped InAsSb/GaSb metamaterial platform, integrable and miniaturized perfect absorbers and thermal sources can be built.