  We demonstrate that 100% light absorption can take place in a single
patterned sheet of doped graphene. General analysis shows that a planar array
of small lossy particles exhibits full absorption under critical-coupling
conditions provided the cross section of each individual particle is comparable
to the area of the lattice unit-cell. Specifically, arrays of doped graphene
nanodisks display full absorption when supported on a substrate under total
internal reflection, and also when lying on a dielectric layer coating a metal.
Our results are relevant for infrared light detectors and sources, which can be
made tunable via electrostatic doping of graphene.
