  We demonstrate generation of chiral modes -- vortex flows with fixed
handedness in exciton-polariton quantum fluids. The chiral modes arise in the
vicinity of exceptional points (non-Hermitian spectral degeneracies) in an
optically-induced resonator for exciton polaritons. In particular, a vortex is
generated by driving two dipole modes of the non-Hermitian ring resonator into
degeneracy. Transition through the exceptional point in the space of the
system's parameters is enabled by precise manipulation of real and imaginary
parts of the closed-wall potential forming the resonator. As the system is
driven to the vicinity of the exceptional point, we observe the formation of a
vortex state with a fixed orbital angular momentum (topological charge). Our
method can be extended to generate high-order orbital angular momentum states
through coalescence of multiple non-Hermitian spectral degeneracies, which
could find application in integrated optoelectronics.
