Title: Active modulation of electromagnetically induced transparency analogue in terahertz hybrid metal-graphene metamaterials,
Abstract: Metamaterial analogues of electromagnetically induced transparency (EIT) have
been intensively studied and widely employed for slow light and enhanced
nonlinear effects. In particular, the active modulation of the EIT analogue and
well-controlled group delay in metamaterials have shown great prospects in
optical communication networks. Previous studies have focused on the optical
control of the EIT analogue by integrating the photoactive materials into the
unit cell, however, the response time is limited by the recovery time of the
excited carriers in these bulk materials. Graphene has recently emerged as an
exceptional optoelectronic material. It shows an ultrafast relaxation time on
the order of picosecond and its conductivity can be tuned via manipulating the
Fermi energy. Here we integrate a monolayer graphene into metal-based terahertz
(THz) metamaterials, and realize a complete modulation in the resonance
strength of the EIT analogue at the accessible Fermi energy. The physical
mechanism lies in the active tuning the damping rate of the dark mode resonator
through the recombination effect of the conductive graphene. Note that the
monolayer morphology in our work is easier to fabricate and manipulate than
isolated fashion. This work presents a novel modulation strategy of the EIT
analogue in the hybrid metamaterials, and pave the way towards designing very
compact slow light devices to meet future demand of ultrafast optical signal
processing.