Matching and funneling light at the plasmonic Brewster angle

Abstract

The ultrabroadband impedance matching of metallic gratings at the plasmonic Brewster angle [A. Al\`u et al., Phys. Rev. Lett. 106, 123902 (2011)] is analyzed here in several realistic scenarios and configurations, and in the case of nonmonochromatic excitation. This phenomenon is the analogy of the well-known Brewster transmission for dielectric slabs but, when applied to plasmonic gratings, has the remarkable property of funneling and concentrating light within subwavelength slits. We analyze here how the presence of absorption and of realistic substrates and/or superstrates may influence the phenomenon, its beamwidth and angular selectivity, and its overall performance in the case of broadband, ultrashort incident pulses in the time domain. We prove that broadband signals may be concentrated and transmitted almost unaffected through narrow apertures, even in the presence of absorption, very different from conventional extraordinary optical transmission based on resonant phenomena.