Single chip scanning lidar and method of producing the same

• US 9,310,471 B2
• Filed: 06/27/2014
• Issued: 04/12/2016
• Est. Priority Date: 06/27/2014
• Status: Active Grant

• Current Assignee: HRL Laboratories LLC (The Boeing Co.)
• Original Assignee: HRL Laboratories LLC (The Boeing Co.)
• Inventors: Sayyah, Keyvan, Patterson, Pamela R., Efimov, Oleg M.
• Primary Examiner(s): Ratcliffe, Luke
• Assistant Examiner(s): Abraham, Samantha K
• Application Number:
  US14/317,695
• Publication Number:
  US 20150378012A1
• Time in Patent Office: 655 Days
• US Class Current: 1/1
• CPC Class Codes: G01S 17/02 Systems using the reflection of electromagnetic waves other than radio waves G01S17/66 takes precedence
• CPC Class Codes: G01S 17/34 using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4808 Evaluating distance, position or velocity data
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: H01S 5/021 Silicon based substrates
• CPC Class Codes: H01S 5/0215 Bonding to the substrate
• CPC Class Codes: H01S 5/0262 Photo-diodes, e.g. transceiver devices, bidirectional devices H01S5/0265 takes precedence
• CPC Class Codes: H01S 5/12 the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers comprising a photonic bandgap structure H01S5/11; surface-emitting lasers H01S5/18

Abstract

A chip-scale scanning lidar includes a two dimensional (2D) scanning micromirror for a transmit beam and a 2D scanning micromirror for a receive beam, a laser diode and a photodetector, a first waveguide and first grating outcoupler coupled to a front facet of the laser diode, a second waveguide and a second grating outcoupler coupled to a rear facet of the laser diode on a substrate. A first fixed micromirror, a second micromirror, a third micromirror, and a focusing component are in a dielectric layer bonded to the substrate over the laser diode and photodetector. The photodetector is optically coupled to the second fixed micromirror and the third fixed micromirror for coherent detection.

Claims

1. A method of fabricating a chip-scale scanning lidar comprising:

forming a two dimensional (2D) scanning micromirror for a transmit beam on a substrate;

forming a two dimensional (2D) scanning micromirror for a receive beam on the substrate;

forming a laser diode on the substrate;

forming a photodetector on the substrate;

forming a first waveguide on the substrate connected on one end of the first waveguide to a first facet of the laser diode;

forming a first grating outcoupler on the substrate connected to another end of the first waveguide;

forming a second waveguide on the substrate connected on one end of the second waveguide to a second facet of the laser diode;

forming a second grating outcoupler on the substrate connected to another end of the second waveguide;

forming a first fixed micromirror and a second fixed micromirror in a first dielectric layer;

forming a third fixed micromirror in a second dielectric layer;

forming a focusing component in a third dielectric layer;

bonding the first, second and third dielectric layers together to form a composite structure;

aligning the composite structure to the substrate over the laser diode and photodetector; and

bonding the composite structure to the substrate over the laser diode and photodetector.

2. The method of claim 1:

wherein forming a laser diode on the substrate comprises;

fabricating the laser diode on a second substrate; and

bonding the second substrate to the substrate;

wherein forming a photodetector on the substrate comprises;

fabricating the photodetector on a third substrate; and

bonding the third substrate to the substrate.

3. The method of claim 1 wherein:

wherein forming a laser diode on the substrate comprises;

bonding laser diode material layers to the substrate using molecular, adhesive, or compression metal bonding techniques; and

processing the laser diode material layers to form the laser diode;

wherein forming a photodetector on the substrate comprises;

bonding photodetector material layers to the substrate using molecular, adhesive, or compression metal bonding techniques; and

processing the photodetector material layers to form the laser diode.

4. The method of claim 1 wherein:

the first waveguide, the second waveguide, the first grating outcoupler, and the second grating outcoupler are formed of material layers transparent at an operating wavelength of the laser diode.

5. The method of claim 4 wherein:

the material layers comprise Si₃N₄ for a core layer and SiO₂ for a cladding layer for an operating wavelength of the laser diode in the visible to the LWIR bands, or the material layers comprise Si for a core layer and SiO₂ for a cladding layer for an operating wavelength of the laser diode in the near-IR to mid-IR bands.

6. The method of claim 1 wherein:

forming the first fixed micromirror and the second fixed micromirror in the first dielectric layer comprises molding techniques;

forming the third fixed micromirror in the second dielectric layer comprises molding techniques; and

forming the microlens in the third dielectric layer comprises molding techniques.

7. The method of claim 1 further comprising:

forming cavities in the third dielectric layer to provide space to fit any vertical extent of the laser diode and the photodetector.

8. The method of claim 1 wherein the two dimensional (2D) scanning micromirror for receiving on the substrate comprises an array of 2-dimensional scanning micromirrors.

9. The method of claim 1 wherein:

the laser diode emits in any spectral band from UV to LWIR; and

the photodiode is responsive in any spectral band from UV to LWIR.

10. The method of claim 1 wherein:

light emitted from the second facet of the laser diode is used as the local oscillator for coherent detection of the received beam by the photodetector.

11. The method of claim 1 wherein:

the laser diode is frequency operates in a pulsed mode, a quasi-continuous wave (CW) mode, or a frequency modulated continuous wave (FMCW) mode.

12. The method of claim 1 further comprising forming post detection lidar processing circuitry on the substrate.

13. The method of claim 1 wherein the focusing component comprises a Fresnel Zone Plate (FZP) or a microlens.

14. The method of claim 1 wherein the laser diode comprises a Distributed Bragg Reflector (DBR) laser or a Distributed Feedback (DFB) laser.

15. The method of claim 1 wherein the 2D scanning micromirror for the receive beam is configured to scan synchronously with the 2D scanning micromirror for the transmit beam.

16. A chip-scale scanning lidar comprising:

a substrate;

a two dimensional (2D) scanning micromirror for a transmit beam on the substrate;

a two dimensional (2D) scanning micromirror for a receive beam on the substrate;

a laser diode on the substrate;

a photodetector on the substrate;

a first waveguide on the substrate connected on one end of the first waveguide to a first facet of the laser diode;

a first grating outcoupler on the substrate connected to another end of the first waveguide;

a second waveguide on the substrate connected on one end of the second waveguide to a second facet of the laser diode;

a second grating outcoupler on the substrate connected to another end of the second waveguide;

a first fixed micromirror in a dielectric layer, the first fixed micromirror optically coupled to the first grating outcoupler;

a second fixed micromirror in the dielectric layer, the second fixed micromirror optically coupled to the second grating outcoupler;

a third fixed micromirror in the dielectric layer the third fixed micromirror optically coupled to the two dimensional (2D) scanning micromirror for the receive beam; and

a focusing component in the dielectric layer the focusing component optically coupled to the third fixed micromirror;

wherein the photodetector is optically coupled to the second fixed micromirror and the third fixed micromirror for coherent detection; and

wherein the dielectric layer is aligned to and bonded to the substrate over the laser diode and photodetector.

17. The lidar of claim 16 wherein:

the first waveguide, the second waveguide, the first grating outcoupler, and the second grating outcoupler comprise material layers transparent at an operating wavelength of the laser diode.

18. The lidar of claim 17 wherein:

the material layers comprise Si₃N₄ for a core layer and SiO₂ for a cladding layer for an operating wavelength of the laser diode in the visible to the LWIR bands, or the material layers comprise Si for a core layer and SiO₂ for a cladding layer for an operating wavelength of the laser diode in the near-IR to mid-IR bands.

19. The lidar of claim 16 further comprising:

cavities in the dielectric layer to provide space to fit any vertical extent of the laser diode and the photodetector.

20. The lidar of claim 16 wherein the two dimensional (2D) scanning micromirror for receiving on the substrate comprises an array of 2-dimensional scanning micromirrors.

21. The lidar of claim 16 wherein:

the laser diode emits in any spectral band from UV to LWIR; and

the photodiode is responsive in any spectral band from UV to LWIR.

22. The lidar of claim 16 wherein:

the laser diode operates in a pulsed mode, a quasi-continuous wave (CW) mode, or a frequency modulated continuous wave (FMCW) mode.

23. The lidar of claim 16 further comprising post detection lidar processing circuitry on the substrate.

24. The lidar of claim 16 wherein the focusing component comprises a Fresnel Zone Plate (FZP) or a microlens.

25. The lidar of claim 16 wherein the laser diode comprises a Distributed Bragg Reflector (DBR) laser or a Distributed Feedback (DFB) laser.

26. The lidar of claim 16 wherein the 2D scanning micromirror for the receive beam is configured to scan synchronously with the 2D scanning micromirror for the transmit beam.

27. The lidar of claim 16 wherein:

light emitted from the second facet of the laser diode is used as the local oscillator for coherent detection of the received beam by the photodetector.