  The ability to control the chirality of physical devices is of great
scientific and technological importance, from investigations of topologically
protected edge states in condensed matter systems to wavefront engineering,
isolation, and unidirectional communication. When dealing with large networks
of oscillators, the control over the chirality of the bulk states becomes
significantly more complicated and requires complex apparatus for generating
asymmetric coupling or artificial gauge fields. Here we present a new approach
for precise control over the chirality of a triangular array of hundreds of
symmetrically-coupled lasers, by introducing a weak non-Hermitian complex
potential, requiring only local on-site control of loss and frequency. In the
unperturbed network, lasing states with opposite chirality (staggered vortex
and staggered anti-vortex) are equally probable. We show that by tuning the
complex potential to an exceptional point, a nearly pure chiral lasing state is
achieved. While our approach is applicable to any oscillators network, we
demonstrate how the inherent non-linearity of the lasers effectively pulls the
network to the exceptional point, making the chirality extremely resilient
against noises and imperfections.
