  Two-dimensional graphene layers exhibit many fascinating properties which
have sparkled into applied research with the aim to build innovative electronic
devices. Here, we theoretically demonstrate that, when the carriers velocity is
constrained along one direction, a monoatomic graphene layer exhibits
dichroism. A fraction $2\pi\alpha$ of the light polarized along the carriers
motion is absorbed, while light polarized perpendicularly to that direction is
not absorbed. A stack of two-dimensional graphene layers whose carriers
velocity is constrained along one direction (such as a stack subjected to a
suitable gate voltage) is thus able to polarize light up to the wished degree
by selective absorption. These findings pave the way for built-in controllable
optical polarizers in upcoming graphene nanoscale devices.
