Absorption Manipulation in a Narrowband Infrared Absorber Based on the Hybridization of Gap Plasmon and Fabry-Perot Resonance

We report a narrowband infrared absorber consisting of a metallic grating separated from a metallic substrate by a dielectric layer. In this absorber, the near-perfect absorption results from the hybridization of the gap plasmon mode and the Fabry-Perot resonance mode. The grating layer acts as an efficient absorbing material because of enhanced electric field in the grating slits, and the absorption spectrum can be manipulated by Fabry-Perot resonance. According to this spectrum manipulation mechanism, the resonance wavelength and bandwidth of absorption can be tuned by changing the dielectric layer thickness. Furthermore, the absorption resonance wavelength can be tuned by changing the incidence angle. This absorption manipulation mechanism can be applied in coherent thermal emitters.