  Ferroelectricity, a spontaneous and reversible electric polarization, is
found in certain classes of van der Waals (vdW) material heterostructures. The
discovery of ferroelectricity in twisted vdW layers provides new opportunities
to engineer spatially dependent electric and optical properties associated with
the configuration of moir\'e superlattice domains and the network of domain
walls. Here, we employ near-field infrared nano-imaging and nano-photocurrent
measurements to study ferroelectricity in minimally twisted WSe2. The
ferroelectric domains are visualized through the imaging of the plasmonic
response in a graphene monolayer adjacent to the moir\'e WSe2 bilayers.
Specifically, we find that the ferroelectric polarization in moir\'e domains is
imprinted on the plasmonic response of the graphene. Complementary
nano-photocurrent measurements demonstrate that the optoelectronic properties
of graphene are also modulated by the proximal ferroelectric domains. Our
approach represents an alternative strategy for studying moir\'e
ferroelectricity at native length scales and opens promising prospects for
(opto)electronic devices.
