  The nonlinear optical and optoelectronic properties of graphene with the
emphasis on the processes of harmonic generation, frequency mixing, photon drag
and photogalvanic effects as well as generation of photocurrents due to
coherent interference effects, are reviewed. The article presents the
state-of-the-art of this subject, including both recent advances and
well-established results. Various physical mechanisms controlling transport are
described in depth including phenomenological description based on symmetry
arguments, models visualizing physics of nonlinear responses, and microscopic
theory of individual effects.
