  Free-space optics (FSO) offer promising solutions in wireless systems where
many different devices need to communicate and interoperate, exchanging massive
amounts of data as in communication and sensor networks, and in technologies
for positioning and ranging. In these applications, control and manipulation of
the light field is required for properly generating and correctly receiving FSO
beams even in the presence of unpredictable objects and turbulence in the light
path. In this work, we use a programmable mesh of Mach-Zehnder Interferometers
(MZIs) to automatically control the complex field radiated and captured by an
array of optical antennas. Several functionalities are demonstrated, including
the generation of perfectly shaped beams with non-perfect optical antennas, the
imaging of a desired field pattern through an obstacle or a diffusive medium,
and the identification of an unknown obstacle inserted in the FSO path.
Compared to conventional devices used for the manipulation of FSO beams, such
as spatial light modulators (SLMs), our programmable circuit can self-configure
through automated control strategies and can be integrated with other
functionalities implemented onto the same photonic chip.
