  We demonstrate a synthetic Hall effect for light, using an acousto-optically
modulated nanophotonic resonator chain. To produce this effect, we
simultaneously generate the required synthetic electric field using temporal
modulation, and the required synthetic magnetic field using spatial modulation
of the resonator chain. We show how the combination of these synthetic fields
transverse to the direction of light propagation can be used to produce
non-reciprocal optical transmission, as a basis for new photonic and
topological devices.
