Planar optical head for free space optical communications, coherent lidar, and other applications

A multi-aperture optical system, comprising:

• a photonic integrated circuit;
• a spacer substrate coupled to the photonic integrated circuit;
• a plurality of optical cells, each optical cell including:
• a focusing optical element formed on the spacer substrate and configured to receive a light incident on the optical cell, and focus the light through the photonic integrated circuit and onto a folding element the folding element being integrated into the photonic integrated circuit to couple light incident on the optical cell into a waveguide, wherein:
• the waveguide is integrated into the photonic integrated circuit, coupled to a phase shifter, and configured to transport the light reflected by the folding element through a phase shifter;
• and
• the phase shifter is coupled to the focusing optical element, and configured to shift a phase of an optical signal received by the focusing optical element;
• a beam combiner coupled to the phase shifters, and configured to combine light output from the phase shifters;
• and
• a photodetector coupled to the beam combiner to receive the combined light output from the beam combiner and output a corresponding signal,
• wherein the photonic integrated circuit, the spacer substrate, the plurality of optical cells, the beam combiner, and the photodetector are integrated as a single monolithically formed optical head.