Methods and Systems for Optical Beam Steering

• US 20170371227A1
• Filed: 06/22/2017
• Published: 12/28/2017
• Est. Priority Date: 06/22/2016
• Status: Active Application

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Mihika Prabhu
• Inventors: SKIRLO, Scott, Sorace-Agaskar, Cheryl Marie, Soljacic, Marin, Verghese, Simon, Herd, Jeffrey S., Juodawlkis, Paul William, Yang, Yi, Englund, Dirk Robert, Prabhu, Mihika
• Granted Patent: US 10,261,389 B2
• Time in Patent Office: Days
• CPC Class Codes: G02F 1/2955 by controlled diffraction or phased-array beam steering controlled diffraction for optical waveguide switching G02F1/313
• CPC Class Codes: G02F 1/311 Cascade arrangement of plural switches
• CPC Class Codes: G02F 1/3136 of interferometric switch type
• CPC Class Codes: G02F 2201/02 fibre
• CPC Class Codes: G02F 2201/06 integrated waveguide
• CPC Class Codes: G02F 2201/302 grating coupler
• CPC Class Codes: G02F 2203/70 Semiconductor optical amplifier [SOA] used in a device covered by G02F

Abstract

An integrated optical beam steering device includes a planar dielectric lens that collimates beams from different inputs in different directions within the lens plane. It also includes an output coupler, such as a grating or photonic crystal, that guides the collimated beams in different directions out of the lens plane. A switch matrix controls which input port is illuminated and hence the in-plane propagation direction of the collimated beam. And a tunable light source changes the wavelength to control the angle at which the collimated beam leaves the plane of the substrate. The device is very efficient, in part because the input port (and thus in-plane propagation direction) can be changed by actuating only log₂ N of the N switches in the switch matrix. It can also be much simpler, smaller, and cheaper because it needs fewer control lines than a conventional optical phased array with the same resolution.

Claims

1. An optical beam steering apparatus comprising:

a substrate;

a plurality of waveguides formed on the substrate, the plurality of waveguides comprising a first waveguide and a second waveguide;

a planar dielectric lens, formed on the substrate in optical communication with the plurality of waveguides, to collimate light emitted by the first waveguide as a first collimated beam propagating in a first direction in a plane of the substrate and to collimate light emitted by the second waveguide as a second collimated beam propagating in a second direction in the plane of the substrate different than the first direction; and

an output coupler, formed on the substrate in optical communication with the planar dielectric lens, to guide the first collimated beam in the first direction and to guide the second collimated beam in the second direction and to couple at least a portion of the first collimated beam and the second collimated beam out of the plane of the substrate.

2. The optical beam steering apparatus of claim 1, wherein the plurality of waveguides comprises at least 32 waveguides in optical communication with the planar dielectric lens.

3. The optical beam steering apparatus of claim 1, wherein the plurality of waveguides comprises at least 100 waveguides in optical communication with the planar dielectric lens.

4. The optical beam steering apparatus of claim 1, wherein the plurality of waveguides comprises at least 1000 waveguides in optical communication with the planar dielectric lens.

5. The optical beam steering apparatus of claim 1, wherein the light emitted by the first waveguide has an arbitrary phase relative to the light emitted by the second waveguide.

6. The optical beam steering apparatus of claim 1, wherein the planar dielectric lens has a shape selected to satisfy the Abbé

sine condition.

7. The optical beam steering apparatus of claim 1, wherein the planar dielectric lens has a single focal point.

8. The optical beam steering apparatus of claim 1, wherein the planar dielectric lens has at least two focal points.

9. The optical beam steering apparatus of claim 1, wherein the output coupler comprises a one-dimensional grating configured to diffract the first collimated beam and the second collimated beam out of the plane of the substrate.

10. The optical beam steering apparatus of claim 1, further comprising:

a tunable light source, in optical communication with the plurality of waveguides, to tune a wavelength of the light emitted by the first waveguide and the light emitted by the second waveguide.

11. The optical beam steering apparatus of claim 10, further comprising:

a network of optical switches, formed on the substrate in optical communication with the tunable light source and the plurality of waveguides, to guide the light emitted by the first waveguide from the tunable light source to the first waveguide when in a first state and to guide the light emitted by the second waveguide from the tunable light source to the second waveguide when in a second state.

12. The optical beam steering apparatus of claim 11, wherein the plurality of waveguides comprises N waveguides and wherein up to log₂ N optical switches in the network of optical switches are actuated to switch from the first state to the second state.

13. The optical beam steering apparatus of claim 11, further comprising:

a plurality of optical amplifiers, formed on the substrate in optical communication with the network of optical switches and the plurality of waveguides, to amplify the light emitted by the first waveguide and the light emitted by the second waveguide.

14. A method of optical beam steering with a plurality of waveguides, a planar dielectric lens, and an output coupler formed on a substrate, the method comprising:

guiding light with a first waveguide in the plurality of waveguides to the planar dielectric lens;

collimating the light emitted by the first waveguide with the planar dielectric lens to produce a first collimated beam propagating in a first direction within a plane of the substrate;

guiding the first collimated beam in the first direction with the output coupler; and

coupling at least a portion of the first collimated beam out of the plane of the substrate with the output coupler.

15. The method of claim 14, further comprising:

guiding light with a second waveguide in the plurality of waveguides to the planar dielectric lens;

collimating the light emitted by the second waveguide with the planar dielectric lens to produce a second collimated beam propagating in a second direction different from the first direction within the plane of the substrate;

guiding the second collimated beam in the second direction with the output coupler; and

coupling at least a portion of the second collimated beam out of the plane of the substrate with the output coupler.

16. The method of claim 15, wherein the light emitted by the first waveguide has an arbitrary phase relative to the light emitted by the second waveguide.

17. The method of claim 14, wherein the planar dielectric lens has a shape selected to satisfy the Abbé

sine condition.

18. The method of claim 14, further comprising:

tuning a wavelength of the light guided with the first waveguide so as to steer the first collimated beam emitted by the output coupler with respect to the plane of the substrate.

19. The method of claim 18, wherein tuning the wavelength comprises steering the first collimated beam to one of at least 15 resolvable angles with respect to a surface normal of the plane of the substrate.

20. The method of claim 18, wherein tuning the wavelength comprises steering the first collimated beam to one of at least 50 resolvable angles with respect to a surface normal of the plane of the substrate.

21. The method of claim 18, wherein tuning the wavelength comprises steering the first collimated beam to one of at least 100 resolvable angles with respect to a surface normal of the plane of the substrate.

22. The method of claim 18, wherein tuning the wavelength comprises steering the first collimated beam to one of at least 1000 resolvable angles with respect to a surface normal of the plane of the substrate.

23. The method of claim 14, further comprising:

guiding the light to the first waveguide with a network of optical switches formed on the substrate.

24. The method of claim 23, wherein the plurality of waveguides comprises N waveguides and further comprising:

actuating up to log₂ N optical switches in the network of optical switches to switch the light from the first waveguide to a second waveguide in the plurality of waveguides.

25. The method of claim 14, further comprising:

amplifying the light guided by the first waveguide with an optical amplifier formed on the substrate in optical communication with the plurality of waveguides.

26. The method of claim 14, further comprising:

receiving light via the output coupler;

guiding the light via the output coupler to the planar dielectric lens; and

coupling the light into a waveguide in the plurality of waveguides with the planar dielectric lens.

27. A lidar comprising:

a light source to emit a beam of light;

a network of optical switches, in optical communication with the tunable light source, to guide the beam of light to a first waveguide in a plurality of waveguides;

a planar dielectric lens, in optical communication with the plurality of waveguides and having a shape selected to satisfy the Abbé

sine condition, to collimate the beam of light emitted by the first waveguide as a first collimated beam propagating in a first direction; and

a periodic structure, in optical communication with the planar dielectric lens, to diffract at least a portion of the first collimated beam at an angle with respect to the first direction.