Methods, systems and devices for free-space optical communications

1. A flat optical terminal comprising:

a plurality of functional layers in a layer stack, with each functional layer implementing a different function of optical compensation and beam processing, the layer stack comprising:

a first layer including an optical phase array;

a second layer stacked on top of the first layer including a liquid crystal modulator or an array of micro-electromechanical elements; and

a third layer stacked on top of the second layer including a polarization grating.

2. The flat optical terminal of claim 1 , wherein the layer stack further comprises a modulation/demodulation layer coupled to the optical phase array in the first layer.

3. The flat optical terminal of claim 1 , wherein the optical phase array includes multiple antenna elements binned in one or more two-dimensional antenna blocks.

4. The flat optical terminal of claim 3 , wherein each of the antenna blocks is connected to a common bus and coupled to a block-associated phase tuning element.

5. The flat optical terminal of claim 1 , wherein the optical phase array includes multiple rows of antenna elements connected in parallel to each other to a common bus.

6. The flat optical terminal of claim 5 , wherein each common bus is configured to be fed via a single phase tuning element per common bus.

7. The flat optical terminal of claim 1 , wherein the multiple antenna elements are overlaid with flat optical lenses.

8. The flat optical terminal of claim 7 , wherein the flat optical lenses are microlenses or Newtonian telescopes made from flat meta-lenses.

9. The flat optical terminal of claim 7 , wherein each antenna element is overlaid with a single flat optical lens.

10. The flat optical terminal of claim 7 , wherein subsets of multiple antenna elements are overlaid with a common flat optical lens.