  Atmospheric turbulences can generate scintillation or beam wandering
phenomena that impairs free space optical (FSO) communication. In this paper,
we propose and demonstrate a proof-of-concept FSO communication receiver based
on a spatial demultiplexer and a photonic integrated circuit coherent combiner.
The system collects the light from several Hermite Gauss spatial modes and
coherently combine on chip the energy from the different modes into a single
output. The FSO receiver is characterized with a wavefront emulator bench that
generates arbitrary phase and intensity patterns. The multimode receiver
presents a strong resilience to wavefront distortions, compared to a monomode
FSO receiver. The system is then used to detect a modulation of the optical
beam through a random wavefront profile.
