Lidar pixel with active polarization control

1. A light detection and ranging (LIDAR) system comprising: a laser that is configured to generate light; a splitter that is configured to split the light into a plurality of split lights; a polarization controller configured to receive a first split light of the plurality of split lights, the polarization controller including a first arm and a second arm, wherein the first arm includes a first phase shifter and a second phase shifter that are configured to be controlled to set a phase of light that passes through the first arm relative to the second arm, wherein the polarization controller includes at least one 2×2 splitter coupled to the first arm and the second arm; and a dual-polarization grating coupler including a first port to receive light from the first arm and a second port configured to receive light from the second arm, wherein the dual-polarization grating coupler is configured to couple the light from the first port into a first beam having a first polarization orientation, and wherein the dual-polarization grating coupler is configured to couple the light from the second arm into a second beam with a second polarization orientation, wherein the first port of the dual polarization grating coupler is optically coupled directly to the second phase shifter.

2. The LIDAR system of claim 1 further comprising:

an optical mixer configured to receive a second light of the plurality of split lights, wherein the dual-polarization grating coupler is configured to couple reflected light having the first polarization orientation into the first arm and configured to couple the reflected light having the second polarization orientation into the second arm,

and wherein the optical mixer is configured to output an output signal in response to the reflected light and the second light,

wherein the reflected light is at least one of the first beam or the second beam reflected from at least one object in a LIDAR operating environment.

3. The LIDAR system of claim 2 , wherein the splitter is coupled to the polarization controller and is coupled to the optical mixer to provide the second light to the optical mixer.

4. The LIDAR system of claim 2 , wherein the at least one 2×2 splitter includes a first 2×2 splitter and a second 2×2 splitter, wherein the polarization controller includes:

a first stage including the first 2×2 splitter and the first phase shifter, wherein the first 2×2 splitter connects to an interconnect that feeds into the optical mixer; and

a second stage including -the second 2×2 splitter and the second phase shifter.

5. The LIDAR system of claim 2 , wherein a polarization of the reflected light is at least partially based on one or more surfaces of the at least one object.

6. The LIDAR system of claim 1 , wherein the second beam with the second polarization orientation is orthogonal to the first polarization orientation.

7. The LIDAR system of claim 1 , wherein the first beam and the second beam superimpose to form a combined beam having an arbitrary polarization.

8. The LIDAR system of claim 7 , wherein the arbitrary polarization is at least partially determined by the first phase shifter and the second phase shifter.

9. An autonomous vehicle control system for an autonomous vehicle, the system comprising: a light detection and ranging (LIDAR) processing engine; and an active polarization controlled coherent pixel array coupled to the LIDAR processing engine, wherein pixels in the active polarization controlled coherent pixel array include: a polarization controller including a first arm and a second arm, wherein the first arm includes a first phase shifter and a second phase shifter that can be controlled to set a phase of the first arm relative to the second arm, wherein the polarization controller includes at least one 2×2 splitter coupled to the first arm and the second arm; and a dual-polarization grating coupler including a first port to receive light from the first arm and a second port configured to receive light from the second arm, wherein the dual-polarization grating coupler is configured to couple the light from the first port into a first beam having a first polarization orientation, and wherein the dual polarization grating coupler is configured to couple the light from the second arm into a second beam with a second polarization orientation, wherein the first port of the dual-polarization grating coupler is optically coupled directly to the second phase shifter.

10. The system of claim 9 , wherein the pixels in the active polarization controlled coherent pixel array includes:

an optical mixer configured to receive a portion of split light, wherein the dual-polarization grating coupler is configured to couple reflected light having the first polarization orientation into the first arm and configured to couple the reflected light having the second polarization orientation into the second arm,

and wherein the optical mixer is configured to output an output signal in response to the reflected light and the portion of split light,

wherein the reflected light is at least one of the first beam or the second beam reflected from at least one object in a LIDAR operating environment.

11. The system of claim 10 , wherein the pixels in the active polarization controlled coherent pixel array includes:

a splitter coupled to the polarization controller and coupled to the optical mixer to provide first light to the polarization controller, the splitter also being configured to provide the second light to the optical mixer, wherein the second light is the portion of split light.

12. The LIDAR system of claim 9 , wherein the first beam and the second beam superimpose to form a combined beam having an arbitrary polarization that is at least partially determined by the first phase shifter and the second phase shifter.

13. A system for an autonomous vehicle, the system comprising:

a light detection and ranging (LIDAR) pixel including:

a polarization controller configured to receive a first portion of split light, wherein the polarization controller includes a first arm and a second arm, and wherein a phase shifter of the polarization controller sets a phase of first-light propagating in the first arm relative to second-light propagating in the second arm, wherein the polarization controller includes at least one 2×2 splitter coupled to the first arm and the second arm;

a grating coupler configured to output an output beam in response to receiving the first-light and the second-light, wherein the grating coupler is configured to receive a reflected beam that is a reflection of the output beam off of an object in a LIDAR operating environment, wherein a first port of the grating coupler is optically coupled directly to the phase shifter; and

an optical mixer configured to output a beat signal in response to receiving a remaining portion of the split light and the reflected beam;

one or more processors configured to control the phase shifter in response to receiving the beat signal from the pixel; and

a control system configured to control the autonomous vehicle in response to the beat signal.

14. The system of claim 13 , wherein the grating coupler is a dual-polarization grating coupler configured to couple the first-light from the first arm into a first beam having a first polarization orientation, and wherein the dual-polarization grating coupler is configured to couple the second-light from the second arm into a second beam with a second polarization orientation orthogonal to the first polarization orientation.

15. The system of claim 13 , wherein the one or more processors control the phase shifter to increase a signal level of the beat signal.

16. The system of claim 13 , wherein the one or more processors control the phase shifter to maximize a signal level of the beat signal.

17. The system of claim 13 , wherein the output beam is an infrared output beam.

18. The system of claim 13 further comprising:

a splitter coupled to the polarization controller and to the optical mixer, wherein the splitter is configured to provide the first portion of the split light to the polarization controller, the splitter also being configured to provide the remaining portion of the split light to the optical mixer.

19. The system of claim 13 , wherein the polarization controller includes a second phase shifter.

20. The system of claim 19 , wherein the at least one 2×2 splitter includes a first 2×2 splitter and a second 2×2 splitter, wherein the polarization controller includes:

a first stage including the first 2×2 splitter and the phase shifter, wherein the first 2×2 splitter connects to an interconnect that feeds into the optical mixer; and

a second stage including the second 2×2 splitter and the second phase shifter.