Controlling Thermal Emission by Parity-Symmetric Fano Resonance of Optical Absorbers in Metasurfaces

In this study, we designed a metasurface based on Al/SiN/Al nanosandwich optical absorbers. Parity-symmetric dark magnetic resonance modes, antisymmetric bright magnetic resonance modes, and surface lattice modes are established simultaneously in such a meta-surface. By changing the structural parameters, the wavelength of the dark mode can be tuned to overlap with the lattice mode. Fano resonance is introduced by coupling between the dark and the lattice modes. Angular-resolved thermal emission experiments showed that the thermal emission induced by the Fano resonance exhibited a narrow wavelength spectrum and directional radiation angle. Fano-type thermal emitters proposed in this work can possibly be used as coherent infrared light sources in the future.