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.

Plasmonic absorption characteristics based on dumbbell-shaped graphene metamaterial arrays

“…In the lower THz range, the interband contributions can be completely ignored. Because of Pauli exclusion principle, the surface conductivity can be approximated as a Drude-like model [41,42].…”

Enhanced THz EIT resonance based on the coupled electric field dropping effect within the undulated meta-surface

“…Recent studies have shown that the EIT effect can be mimicked by a series of classical optical systems, such as on-chip plasmonic structures [2], photonic crystals [3][4][5] and meta-surfaces [6][7][8][9][10]. Apart from its fundamental significance, meta-surface-induced transparency in subwavelength structures is the most recent and promising addition to the existing classical EIT schemes [11][12][13]. Terahertz bandpass devices, such as the THz modulators and sensing devices [14], have been developed by applying the transparency window of the EIT.…”

“…Gu et al observed the excitation and tuning of EIT by the interference between different excitation pathways of the dark mode in a planar terahertz metamaterial [10]. Xiao et al realize a complete modulation in the resonance strength of the EIT analog via manipulating the conductivity of graphene [11].…”

Actively tunable terahertz electromagnetically induced transparency analogue based on vanadium-oxide-assisted metamaterials

“…Compared with the conventional EIT, which requires severe experimental conditions [18], MM-based EIT analogue is easier to be produced and more stable, therefore suitable for practical chipscale applications [15].At the same time, for THz communication systems, THz devices with active tunability are required [19]. Therefore, various active optical materials have been utilized to turn passive MMs to be active, including liquid crystals [20,21], semiconductors [19,22,23], two-dimension (2D) materials [24][25][26] and phase-change materials (PCMs) [27]. PCMs, such as chalcogenide GeSbTe (GST) and vanadium dioxide (VO2), possess significantly different optical properties in different phase states, i.e., amorphous and crystalline states [28].…”