  Electrically tuneable high mobility charges on graphene yield an efficient
electro-optical platform to control and manipulate terahertz (THz) waves.
Real-world applications require a multiplex THz device with efficient
modulation over a large active area. The trade-off between the efficient gating
and switching speed, however, hinders the realization of these applications.
Here, we demonstrate a large-format 256-pixel THz modulator which provides
high-frame-rate reconfigurable transmission patterns. The time-domain and
frequency-domain THz characterizations of graphene devices reveal the
relaxation pathways of gate-induced charges and ion packing at
graphene-electrolyte interface. The fundamental understanding of these limiting
factors enables us to break the trade-off permitting switching frequencies up
to 1 kHz. To show the promises of these devices, we demonstrate a single-pixel
THz camera which allows spatial and spectroscopic imaging of large-area objects
without any moving components. These results provide a significant advancement
towards the achievement of non-invasive THz imaging systems using
graphene-based platforms.
