Optical phased arrays with evanescently-coupled antennas

A method of creating a far-field radiation pattern in the far field of an optical phased array from a coherent optical beam having a free-space wavelength λ0, the optical phased array comprising at least one waveguide and a plurality of antenna elements disposed in a plane of the at least one waveguide, the method comprising:

• (A) guiding the coherent optical beam via the at least one waveguide;
• (B) evanescently coupling respective portions of the coherent optical beam from the at least one waveguide to respective antenna elements in the plurality of antenna elements;
• and
• (C) emitting the respective portions of the coherent optical beam from the respective antenna elements so as to produce the far-field radiation pattern.

An optical phased array to form a far-field radiation pattern from a coherent optical beam having a free-space wavelength of about λ0, the optical phased array comprising:

• a substrate;
• a column waveguide, formed in or on the substrate, to guide the coherent optical beam;
• a plurality of directional couplers, formed in or on the substrate, to evanescently couple respective portions of the coherent optical beam from the column waveguide so as to produce a plurality of row beams;
• a plurality of row waveguides, formed in or on the substrate, each row waveguide in the plurality of row waveguides in optical communication with a corresponding directional coupler in the plurality of directional couplers, to guide the plurality of row beams;
• a plurality of phase shifters, formed in or on the substrate, each phase shifter in the plurality of phase shifters evanescently coupled to a corresponding row waveguide in the plurality of row waveguides and configured to impart a corresponding phase shift to a corresponding portion of the corresponding row beam in the plurality of row beams so as to produce a corresponding phase-shifted beam;
• a plurality of antenna elements, formed in or on the substrate, each antenna element in the plurality of antenna elements in optical communication with a corresponding phase shifter in the plurality of phase shifters and configured to emit the corresponding phase-shifted beam at an angle with respect to the substrate so as to form the far-field radiation pattern;
• and
• a plurality of independently controllable heaters, each independently controllable heater in the plurality of independently controllable heaters in thermal communication with a corresponding phase shifter in the plurality of phase shifters and configured to heat the respective phase shifter so as to vary the corresponding phase shift in order to vary the far-field radiation pattern and/or to compensate for phase error in the column waveguide and/or the plurality of row waveguides.