  Light modulation is an essential operation in photonics and optoelectronics.
With existing and emerging technologies increasingly demanding compact,
efficient, fast and broadband optical modulators, high-performance light
modulation solutions are becoming indispensable. The recent realization that
two-dimensional layered materials could modulate light with superior
performance has prompted intense research and significant advances, paving the
way for realistic applications. In this review, we cover the state-of-the-art
of optical modulators based on two-dimensional layered materials including
graphene, transition metal dichalcogenides and black phosphorus. We discuss
recent advances employing hybrid structures, such as two-dimensional
heterostructures, plasmonic structures, and silicon/fibre integrated
structures. We also take a look at future perspectives and discuss the
potential of yet relatively unexplored mechanisms such as magneto-optic and
acousto-optic modulation.
