Active modulation of electromagnetically induced transparency analogue in terahertz hybrid metal-graphene metamaterials

摘要

Metamaterial analogues of electromagnetically induced transparency (EIT) havebeen intensively studied and widely employed for slow light and enhancednonlinear effects. In particular, the active modulation of the EIT analogue andwell-controlled group delay in metamaterials have shown great prospects inoptical communication networks. Previous studies have focused on the opticalcontrol of the EIT analogue by integrating the photoactive materials into theunit cell, however, the response time is limited by the recovery time of theexcited carriers in these bulk materials. Graphene has recently emerged as anexceptional optoelectronic material. It shows an ultrafast relaxation time onthe order of picosecond and its conductivity can be tuned via manipulating theFermi energy. Here we integrate a monolayer graphene into metal-based terahertz(THz) metamaterials, and realize a complete modulation in the resonancestrength of the EIT analogue at the accessible Fermi energy. The physicalmechanism lies in the active tuning the damping rate of the dark mode resonatorthrough the recombination effect of the conductive graphene. Note that themonolayer morphology in our work is easier to fabricate and manipulate thanisolated fashion. This work presents a novel modulation strategy of the EITanalogue in the hybrid metamaterials, and pave the way towards designing verycompact slow light devices to meet future demand of ultrafast optical signalprocessing.