Tunable large resonant absorption in a midinfrared graphene Salisbury screen

Abstract

The optical absorption properties of periodically patterned graphene plasmonic resonators are studied experimentally as the graphene sheet is placed near a metallic reflector. By varying the size and carrier density of the graphene, the parameters for achieving a surface impedance closely matched to free-space $({Z}_{0}\phantom{\rule{0.16em}{0ex}}=\phantom{\rule{0.16em}{0ex}}377\phantom{\rule{0.16em}{0ex}}\ensuremath{\Omega})$ are determined and shown to result in 24.5% total optical absorption in the graphene sheet. Theoretical analysis shows that complete absorption is achievable with higher doping or lower loss. This geometry, known as a Salisbury screen, provides an efficient means of light coupling to the highly confined graphene plasmonic modes for future optoelectronic applications.