Active spatial control of terahertz plasmons in graphene

Graphene offers the possibility for actively controlling plasmon confinement and propagation by tailoring its spatial conductivity. However, implementation of this concept has been hampered because it is difficult to control the conductivity pattern without disturbing the electromagnetic environment of graphene plasmons. Here we demonstrate full electrical control of plasmon reflection/transmission in graphene at electronic boundaries induced by a transparent patterned zinc oxide gate, which is designed to minimize the electromagnetic coupling to graphene in the terahertz range. This approach enables plasmons to be confined to desired regions. Our approach might be applied to various types of plasmonic devices, paving the way for implementing a programmable plasmonic circuit. Controlling spatial conductivity in graphene is important for plasmonic devices, yet conductivity patterning typically changes the electromagnetic environment. Here, teraherz plasmons in graphene are confined to specific regions via a patterned zinc oxide gate, reducing electromagnetic coupling.