  We show that a transition metal dichalcogenide monolayer with a radiatively
broadened exciton resonance would exhibit perfect extinction of a transmitted
field. This result holds for s- or p-polarized weak resonant light fields at
any incidence angle, due to the conservation of in-plane momentum of excitons
and photons in a flat defect-free two dimensional crystal. In contrast to
extinction experiments with single quantum emitters, exciton-exciton
interactions lead to an enhancement of reflection with increasing power for
incident fields that are blue detuned with respect to the exciton resonance. We
show that the interactions limit the maximum reflection that can be achieved by
depleting the incoming coherent state into an outgoing two-mode squeezed state.
