  Graphene is a mechanically robust 2D material promising for flexible
optoelectronic applications. However, its electromagnetic properties under
strain are experimentally poorly understood. Here we present the far-infrared
transmission spectra of large-area chemical-vapor deposited monolayer graphene
on a polyethylene terephthalate substrate subjected to uniaxial strain. The
effective strain value is calibrated using the Raman spectroscopy and corrected
for a relaxation of wrinkles and folds seen directly by atomic-force
microscopy. We find that while the Drude weight and the Fermi level remain
constant, the scattering rate increases by more than 10% per 1% of applied
strain, showing a high level of reproducibility during strain cycling. As a
result, the electronic mobility and optical absorption of graphene at terahertz
and lower frequencies appear to also be sensitive to strain, which opens
pathways to control these key parameters mechanically. We suggest that such a
functionality can be potentially used in flexible optoelectronic and
microelectromechanical systems based on graphene. By combining our findings
with existing theoretical models, we discuss the possible mechanisms of
strain-controlled Drude scattering.
