Self-mixing interference device for sensing applications

Patent metadata

Field	Value
Publication number	US-12345529-B2
Application number	US-202318094255-A
Country	US
Kind code	B2
Filing date	Jan 6, 2023
Priority date	Jul 1, 2019
Publication date	Jul 1, 2025
Grant date	Jul 1, 2025

Abstract

Disclosed herein are self-mixing interferometry (SMI) sensors, such as may include vertical cavity surface emitting laser (VCSEL) diodes and resonance cavity photodetectors (RCPDs). Structures for the VCSEL diodes and RCPDs are disclosed. In some embodiments, a VCSEL diode and an RCPD are laterally adjacent and formed from a common set of semiconductor layers epitaxially formed on a common substrate. In some embodiments, a first and a second VCSEL diode are laterally adjacent and formed from a common set of semiconductor layers epitaxially formed on a common substrate, and an RCPD is formed on the second VCSEL diode. In some embodiments, a VCSEL diode may include two quantum well layers, with a tunnel junction layer between them. In some embodiments, an RCPD may be vertically integrated with a VCSEL diode.

First claim

What is claimed is:

1. A self-mixing interferometry (SMI) sensor, comprising
a resonant cavity photodetector (RCPD) comprising a first set of semiconductor layers formed on a substrate, wherein the first set of semiconductor layers include:
a first emission side distributed Bragg reflector;
a first base side distributed Bragg reflector; and
a first active region layer positioned between the first emission side distributed Bragg reflector and the first base side distributed Bragg reflector; and

a vertical cavity surface emitting laser (VCSEL) diode comprising a second set of semiconductor layers formed on the first set of semiconductor layers, wherein the second set of semiconductor layers include:
a second emission side distributed Bragg reflector;
a second base side distributed Bragg reflector; and
a second active region layer positioned between the second emission side distributed Bragg reflector and the second base side distributed Bragg reflector.

2. The SMI sensor of claim 1 , wherein:
the first set of semiconductor layers laterally extend beyond the second set of semiconductor layers; and
an etch stop layer is positioned between the first set of semiconductor layers and the second set of semiconductor layers.

3. The SMI sensor of claim 2 , further comprising:
first and second electrical supply contacts positioned on an upper surface of the VCSEL diode; and
a third electrical supply contact positioned on a portion of the second set of semiconductor layers that laterally extends beyond the first set of semiconductor layers.

4. The SMI sensor of claim 3 , wherein:
the VCSEL diode is configured to emit a laser light toward an object under forward bias to the first and second electrical supply contacts; and
the RCPD is configured to receive second reflections or backscatters of the emitted laser light from the object under a reverse bias to the third electrical supply contact.

5. The SMI sensor of claim 1 , further comprising a ground contact layer coupled to the substrate, wherein the ground contact layer is positioned on an opposite side of the substrate as the first set of semiconductor layers.

6. The SMI sensor of claim 1 , further comprising processing circuitry configured to:
measure a measurable parameter produced by the RCPD; and
determine at least one of a displacement or a motion of an object using at least the measured parameter.

7. The SMI sensor of claim 1 , wherein:
the VCSEL diode is configured to emit a laser light under forward bias;
a first portion of the emitted laser light is directed toward an object separate from the SMI sensor; and
a second portion of the emitted laser light is directed toward the RCPD.

8. The SMI sensor of claim 1 , wherein the VCSEL diode is configured to emit laser light with a natural wavelength of 940 nanometers.

9. A self-mixing interferometry (SMI) sensor, comprising:
a first set of semiconductor layers formed on a substrate, wherein the first set of semiconductor layers include a first active region layer positioned between a first emission side distributed Bragg reflector and a first base side distributed Bragg reflector;
a vertical cavity surface emitting laser (VCSEL) diode comprising a second set of semiconductor layers formed on the first set of semiconductor layers, wherein the second set of semiconductor layers include a second active region layer positioned between a second emission side distributed Bragg reflector and the second base side distributed Bragg reflector; and
a third set of semiconductor layers formed on the substrate and positioned laterally adjacent to the first set of semiconductor layers.

10. The SMI sensor of claim 9 , wherein the third set of semiconductor layers include a third active region layer positioned between a first emission side distributed Bragg reflector and a first base side distributed Bragg reflector.

11. The SMI sensor of claim 9 , wherein the VCSEL diode is configured to emit a laser light while forward biased and undergo self-mixing interference caused by receiving first reflections or backscatters from an object.

12. The SMI sensor of claim 11 , wherein:
the first set of semiconductor layers is configured to receive second reflections or backscatters of the emitted laser light from the object;
the second set of semiconductor layers is configured to receive third reflections or backscatters of the emitted laser light from the object; and
determine at least one of a displacement or a motion of the object using outputs from the first set of semiconductor layers and the second set of semiconductor layers.

13. The SMI sensor of claim 11 , wherein the first set of semiconductor layers and the second set of semiconductor layers are configured to be reverse biased during emission of the laser light by the VCSEL diode.

14. The SMI sensor of claim 9 , further comprising:
first and second electrical supply contacts positioned on an upper surface of the VCSEL diode; and
third and fourth electrical supply contacts positioned on an upper surface of the second RCPD.

15. The SMI sensor of claim 14 , wherein the first set of semiconductor layers and the third set of semiconductor layers are a same set of semiconductor layers, separated by a trench.

16. A self-mixing interferometry (SMI) sensor, comprising:
a resonant cavity photodetector (RCPD) comprising a first set of semiconductor layers formed on a substrate; and
a vertical cavity surface emitting laser (VCSEL) diode formed over the RCPD and comprising a second set of semiconductor layers formed on the first set of semiconductor layers; and
an etch stop layer between the first set of semiconductor layers and the second set of semiconductor layers;
wherein:
the VCSEL diode is configured to emit laser light when forward biased and undergo self-mixing interference upon reception of reflections or backscatters of the emitted laser light from an object, the self-mixing interference altering a property of the emitted laser light; and
the RCPD is configured to be reverse biased during emission of the laser light by the VCSEL diode and detect an alteration in the property of the emitted laser light.

17. The SMI sensor of claim 16 , wherein:
the VCSEL diode additionally comprises a forward biased quantum well to emit light; and
the RCPD additionally comprises a reverse biased quantum well to absorb light.

18. The SMI sensor of claim 16 , wherein the RCPD is a first RCPD and further comprising a second RCPD positioned laterally adjacent the first RCDP and comprising a third set of semiconductor layers formed on the substrate.

19. The SMI sensor of claim 18 , further comprising processing circuitry that is configured to determine at least one of a displacement or a motion of the object using outputs from the first RCPD and the second RCPD.

Assignees

• Apple Inc

Inventors

• Tan Fei
• Laflaquiere Arnaud
• Lin Chin Han
• Lyon Keith
• Drader Marc A
• Li Weiping

Classifications

• G01S7/4916 Primary

  using self-mixing in the laser cavity · CPC title

• G01S17/34

  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 title

• H01S5/183

  having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL] · CPC title

• G01B11/026

  by measuring distance between sensor and object (G01B11/0608 takes precedence) · CPC title

• G01B9/02092

  Self-mixing interferometers, i.e. feedback of light from object into laser cavity · CPC title