Speckle reduction in photonic phased arrays

1. An optical phased-array device comprising:

at least one array of phase-controlled elements; and

at least one optical network in communication with the phase-controlled elements;

wherein said optical phased-array device is configured such that it includes:

at least one transmitter aperture from which an optical signal is emitted; and

multiple receiver apertures into which backscattered optical energy is collected along a respective acceptance angle;

wherein at least a first of the receiver apertures includes a first subset of the phase-controlled elements of the array of phase-controlled elements coupled in a first portion of the optical network and a second subset of the phase-controlled elements of the array of phase-controlled elements coupled in a second portion of the optical network; and

wherein at least the first of the receiver apertures is configured to provide:

optical energy coupled through the first portion of the optical network to a first optical detector in a detector structure that is operationally connected to a local oscillator that is coherent with the emitted optical signal; and

optical energy coupled through the second portion of the optical network to a second optical detector in the detector structure different from the first optical detector in the detector structure.

2. The optical phased-array device of claim 1 , further comprising:

a respective detector structure associated with each of the receiver apertures.

3. The optical phased-array device of claim 2 , further comprising:

a respective amplifier connected to and associated with each detector structure;

a processor connected to each detector structure via the associated amplifier; and

a local oscillator operationally connected to each detector structure.

4. The optical phased-array device of claim 1 , wherein the at least one optical network comprises:

a first optical collection network in communication with phase-controlled elements of a first array of phase-controlled elements included in a first receiver aperture of the multiple receiver apertures; and

a second optical collection network in communication with phase-controlled elements of a first array of phase-controlled elements included in a second receiver aperture of the multiple receiver apertures.

5. The optical phased-array device of claim 4 , wherein the at least one optical network further comprises:

an optical distribution network in communication with phase-controlled elements of a third array of phase-controlled elements included in the transmitter aperture.

6. The optical phased-array device of claim 1 , wherein the detector structure comprises: a coherent detection arrangement including a splitter and at least two optical detectors, and wherein the local oscillator is operationally connected to the at least two optical detectors via the splitter.

7. The optical phased-array device of claim 1 , wherein the detector structure comprises: at least two optical detectors in an in-phase/quadrature (I/Q detection arrangement including at least one 90 degree hybrid component that provides in-phase and quadrature outputs that have a relative 90 degree phase shift with respect to each other, and wherein the local oscillator is operationally connected to the at least two optical detectors via the 90 degree hybrid component.

8. The optical phased-array device of claim 1 , wherein the at least one transmitter aperture is a single transmitter aperture.

9. The optical phased-array device of claim 1 , wherein at least two of the receiver apertures include at least some of the phase-controlled elements of the array of phase-controlled elements.

10. The optical phased-array device of claim 9 , wherein the receiver apertures are arranged along an axis in a plane in which the phase-controlled elements are configured to provide steering of the respective acceptance angles using phases of the phase-controlled elements.

11. A method comprising:

providing at least one optical wave to an optical network in communication with an array of phase-controlled elements;

emitting an optical signal from at least one transmitter aperture that includes at least some of the phase-controlled elements;

receiving backscattered optical energy into multiple receiver apertures, wherein a first of the receiver apertures includes a first subset of the phase-controlled elements of the array of phase-controlled elements coupled in a first portion of the optical network and a second subset of the phase-controlled elements of the array of phase-controlled elements coupled in a second portion of the optical network, and the backscattered optical energy is collected into each of the receiver apertures along a respective acceptance angle; and

providing from at least one of the receiver apertures:

optical energy coupled through the first portion of the optical network to a first optical detector in a detector structure that is operationally connected to a local oscillator that is coherent with the emitted optical signal; and

optical energy coupled through the second portion of the optical network to a second optical detector in the detector structure different from the first optical detector in the detector structure.

12. The method of claim 11 , wherein electrical signals generated by the first optical detector and the second optical detector are post-processed and added electronically.

13. The method of claim 11 , wherein a speckle pattern of backscattered optical energy collected into the first of the receiver apertures includes variations smaller than a size of an array of phase-controlled elements included in the first of the receiver apertures, and portions of different modes of the speckle pattern are directed to different optical detectors in the detector structure.

14. The optical phased-array device of claim 1 , wherein the first portion of the optical network and the second portion of the optical network include at least one M×N coupler in common, where M and N are both >1.

15. The optical phased-array device of claim 1 , wherein the first optical detector and the second optical detector are coupled to different levels of the optical network.