Ultrabroadband absorber using a deep metallic grating with narrow slits

We report an ultrabroadband absorber using a deep metallic grating with narrow slits in the infrared regime. In this absorber, the ultrabroadband electromagnetic wave has been perfectly transmitted through the vacuum-grating interface due to the plasmonic Brewster angle effect, and its energy can attenuate effectively through the slits because of the enhanced electric field inside the slits. In addition, simulation results show that this ultrabroadband absorber works over a narrow angle range which is a very important feature of directional thermal source.