Aberration correction of optical phased arrays

Patent metadata

Field	Value
Publication number	US-10976542-B2
Application number	US-201916260016-A
Country	US
Kind code	B2
Filing date	Jan 28, 2019
Priority date	Jan 26, 2018
Publication date	Apr 13, 2021
Grant date	Apr 13, 2021

Abstract

Aspects of the present disclosure describe systems, methods, and structures for aberration correction of optical phased arrays that employ a corrective optical path difference (OPD) in the near-field of an OPA to correct or cancel out aberrations in emitted beams of the OPA including those reaching far-field distances by generating a spatially-varying OPD across the aperture of the OPA that is substantially equal and opposite to an equivalent OPD of the aberration(s).

First claim

The invention claimed is:

1. An optical phased array (OPA) structure comprising:
an array of optical antennas that emit light, said array of antennas defining an overall aperture of the OPA; and
a phase corrector configured to apply at least one of: (1) a spatially-varying optical path difference (OPD) across the overall aperture of the OPA, where the spatially-varying OPD is substantially equal and opposite to an equivalent OPD that would cause any far-field beam aberrations, or (2) a spatially-varying optical phase shift across the overall aperture of the OPA, where the spatially-varying optical phase shift is substantially equal and opposite to an equivalent optical phase shift that would cause any far-field beam aberrations;
wherein the overall aperture of the OPA is arranged as a plurality of sub-apertures, and the phase corrector comprises a plurality of index-controlling elements underlying the OPA structure, each one of the index-controlling elements associated with a particular sub-aperture, and each one of the index-controlling elements operable to adjust at least one of the OPD or optical phase shift of the sub-aperture to which it is associated.

2. The OPA structure of claim 1 wherein:
the plurality of index-controlling elements comprise a plurality of individually operable heater elements in thermal communication with the overall aperture.

3. The OPA structure of claim 1 wherein:
the plurality of index-controlling elements comprise a plurality of individually operable electrodes positioned within the overall aperture.

4. The OPA structure of claim 1 further comprising:
a plurality of individually operable phase shifters positioned outside of the overall aperture, each one of the phase shifters positioned in an optical path at the entrance to an optical waveguide, said waveguide including a plurality of antennae, wherein at least one antenna of the plurality of antennae is positioned in a different sub-aperture from another antenna of the same waveguide.

5. The OPA structure of claim 2 wherein:
a change in at least one of OPD or optical phase shift of antennae associated with a particular sub-aperture occurs when the heater element associated with that particular sub-aperture is activated.

6. The OPA structure of claim 3 wherein:
a change in at least one of OPD or optical phase shift of antennae associated with a particular sub-aperture occurs when a voltage is applied to the electrode associated with that particular sub-aperture.

7. The OPA structure of claim 1 wherein:
at least two of the antennae share a common waveguide, each one of the two antennae associated with a different sub-aperture, wherein at least one of the index-controlling elements is positioned intermediate to the two antennae.

8. The OPA structure of claim 1 wherein:
the plurality of index-controlling elements comprise a plurality of electrodes underlying the OPA structure on a surface opposite to an OPA surface including the antennae.

9. A method for aberration correction of an optical phased array (OPA), the method comprising:
operating the optical phased array such that light is emitted into a far-field of the OPA;
detecting the far-field light;
determining, from the detected far-field light, OPA aberrations; and
applying using a phase corrector, from the determined OPA aberrations, at least one of:
(1) a spatially-varying optical path difference (OPD) across an overall aperture of the OPA, or (2) a spatially-varying optical phase shift across the overall aperture of the OPA;

wherein the overall aperture of the OPA is arranged as a plurality of sub-apertures, and the phase corrector comprises a plurality of index-controlling elements underlying the OPA, each one of the index-controlling elements associated with a particular sub-aperture, and each one of the index-controlling elements adjusting at least one of the OPD or optical phase shift of the sub-aperture to which it is associated.

10. The method of claim 9 wherein:
the plurality of index-controlling elements comprise a plurality of individually operable electrodes positioned within the overall aperture, and the applied OPD or optical phase shift is effected by application of a voltage to one or more of the individually operable electrodes.

11. The method of claim 9 wherein:
the plurality of index-controlling elements comprise a plurality of individually operable heater elements positioned within the OPA, and the applied OPD or optical phase shift is effected by activation of one or more of the individually operable heater elements.

12. A method for aberration correction of an optical phased array (OPA), the method comprising:
determining any variations in characteristics of waveguides comprising the OPA;
determining from the determined variations in waveguide characteristics a spatially-varying optical path difference (OPD) or a spatially-varying optical phase shift to be applied to sub-apertures within an overall aperture of the OPA such that a predetermined far-field emission pattern of the OPA is achieved; and
applying the spatially-varying OPD or optical phase shift to the aperture using a plurality of index-controlling elements underlying the OPA, each one of the index-controlling elements associated with a particular sub-aperture, and each one of the index-controlling elements operable to adjust at least one of the OPD or optical phase shift of the sub-aperture to which it is associated.

13. The method of claim 12 wherein:
the plurality of index-controlling elements comprise a plurality of heater elements in thermal communication with particular ones of the plurality of waveguides.

14. The method of claim 12 wherein:
the plurality of index-controlling elements include at least one index-controlling element positioned intermediate to a pair of antenna emitter structures in optical communication with a particular one of the plurality of waveguides.

15. The OPA structure of claim 1 wherein:
at least one of the index-controlling elements is configured to induce a spatially-varying index of a waveguide in optical communication with one or more of the antennas.

16. The OPA structure of claim 15 wherein:
the index-controlling element induces the spatially-varying index by breaking down a crystalline structure of a material of the waveguide or a material in proximity to the waveguide, or by crystalizing an amorphous material of the waveguide or a material in proximity to the waveguide.

17. The method of claim 9 wherein:
at least one of the OPD or optical phase shift adjusted by one or more of the index-controlling elements comprises a spatially-varying index of a waveguide in optical communication with one or more antennas of an array of optical antennas providing the emitted light.

18. The method of claim 17 wherein:
applying the spatially-varying index comprises breaking down a crystalline structure of a material of the waveguide or a material in proximity to the waveguide, or crystalizing an amorphous material of the waveguide or a material in proximity to the waveguide.

19. The method of claim 12 wherein determining any variations in characteristics of waveguides comprising the OPA comprises: measuring resonance frequencies associated with optical resonators positioned in proximity to optical antennas at locations along the waveguides.

Assignees

• Analog Photonics LLC

Inventors

• Russo Peter Nicholas
• Hosseini Ehsan
• Poulton Christopher
• Timurdogan Erman
• Vermeulen Diedrik
• Watts Michael Robert
• Whitson Michael

Classifications

• G02B27/0068 Primary

  having means for controlling the degree of correction, e.g. using phase modulators, movable elements (controlling the phase of light using moving or deformable elements G02B26/06) · CPC title

• G02B27/0087

  Phased arrays · CPC title

• G02F2203/18

  adaptive optics, e.g. wavefront correction · CPC title

• G02F1/2955

  by controlled diffraction or phased-array beam steering (controlled diffraction for optical waveguide switching G02F1/313) · CPC title

• H04B10/50

  Transmitters · CPC title