Coherent Feedback Control Of Two-Dimensional Excitons

Electric dipole radiation can be controlled by engineering of the photonic environment. A coherent interaction between forward and backward emission depends interferometrically on the position of a nearby mirror. The transverse coherence of exciton emission in a single layer of MoSe2 and the highly radiatively broadened nature of our samples removes fundamental physical limitations of previous experiments employing pointlike dipoles. This enables full control over the exciton radiative coupling rate and total linewidth at cryogenic temperatures from near zero to 1.8 +/- 0.4 meV and from 0.9 to 2.3 +/- 0.1 meV, respectively.