Self-Mixing Interference Device for Sensing Applications

Patent metadata

Field	Value
Publication number	US-2023152081-A1
Application number	US-202318094255-A
Country	US
Kind code	A1
Filing date	Jan 6, 2023
Priority date	Jul 1, 2019
Publication date	May 18, 2023
Grant date	—

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 vertical cavity surface emitting laser (VCSEL) diode; and a resonant cavity photodetector (RCPD) laterally adjacent to the VCSEL diode; wherein: the VCSEL diode and the RCPD include a common set of semiconductor layers formed on a common substrate; the common set of semiconductor layers includes an active region layer; the VCSEL diode and the RCPD are at least partially separated by a trench extending at least partially through the common set of semiconductor layers, the trench extending through the active region layer; and the VCSEL diode comprises additional semiconductor layers stacked with the common set of semiconductor layers.

2 . The SMI sensor of claim 1 , wherein:
the additional semiconductor layers comprise an etch stop layer adjacent to the common set of semiconductor layers; and a bias supply electrical contact is connected to a layer of the additional semiconductor layers farthest from the common set of semiconductor layers.

3 . The SMI sensor of claim 2 , wherein the additional semiconductor layers are formed on the common set of semiconductor layers.

4 . The SMI sensor of claim 1 , wherein:
the VCSEL diode is configured to emit a laser light under forward bias and undergo self-mixing interference caused by first reflections or backscatters of the emitted laser light from an object, the self-mixing interference altering a property of the emitted laser light; the RCPD is configured to be reverse biased during emission of the laser light by the VCSEL diode and receive second reflections or backscatters of the emitted laser light from the object; and the RCPD produces a measurable parameter related to the altered property of the emitted laser light.

5 . The SMI sensor of claim 4 , further comprising:
processing circuitry configured to:
measure the measurable parameter produced by the RCPD; and
determine at least one of a displacement or a motion of the object using at least the measured parameter.

6 . The SMI sensor of claim 4 , wherein the VCSEL diode is configured to emit the laser light with a natural wavelength of 940 nanometers.

7 . The SMI sensor of claim 1 , wherein the active region layer within the RCPD is doped to have a narrower band gap than the active region layer within the VCSEL diode.

8 . A self-mixing interferometry (SMI) sensor, comprising:
a first vertical cavity surface emitting laser (VCSEL) diode; a second VCSEL diode laterally adjacent to the first VCSEL diode; and a resonant cavity photodetector (RCPD); wherein: the first VCSEL diode and the second VCSEL diode include a common set of semiconductor layers formed on a common substrate; the common set of semiconductor layers includes an active region layer; the first VCSEL diode and the second VCSEL diode are at least partially separated by a trench extending at least partially through the common set of semiconductor layers; and the RCPD is positioned vertically adjacent to the second VCSEL diode on a side of the second VCSEL diode opposite to the common substrate.

9 . The SMI sensor of claim 8 , wherein:
the first 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, the self-mixing interference altering a property of the emitted laser light; the RCPD and the second VCSEL diode are configured to be reverse biased during emission of the laser light by the first VCSEL diode; the RCPD is configured to receive second reflections or backscatters of the emitted laser light from the object; and the altered property of the emitted laser light is detectable using a measured parameter of the RCPD.

10 . The SMI sensor of claim 8 , wherein the RCPD comprises a junction layer containing a first semiconductor material different from a second semiconductor material in the active region layer.

11 . The SMI sensor of claim 10 , wherein the first semiconductor material of the junction layer of the RCPD is Indium Gallium Arsenide.

12 . The SMI sensor of claim 8 , further comprising an etch stop layer between the RCPD and the second VCSEL diode.

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

14 . The SMI sensor of claim 8 , wherein the active region layer comprises:
a first active region layer; a second active region layer; and a tunnel junction layer between the first active region layer and the second active region layer.

15 . The SMI sensor of claim 14 , wherein the tunnel junction layer comprises a first sublayer comprising a highly doped n-type semiconductor and a second sublayer comprising a highly doped p-type semiconductor.

16 . The SMI sensor of claim 14 , wherein:
the first VCSEL diode has an emission side distributed Bragg reflector with a reflectance of less than 99.0%.

17 . The SMI sensor of claim 8 , wherein:
the RCPD comprises an emission side distributed Bragg reflector and a base side distributed Bragg reflector; and the emission side distributed Bragg reflector has fewer Bragg pairs than the base side distributed Bragg reflector.

18 . A self-mixing interferometry (SMI) sensor, comprising:
a vertical cavity surface emitting laser (VCSEL) diode; and a resonant cavity photodetector (RCPD) vertically adjacent to the VCSEL diode; wherein: the VCSEL diode comprises a first set of semiconductor layers formed on a substrate; the RCPD comprises a second set of semiconductor layers formed on the first set of semiconductor layers opposite to the substrate; 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 the alteration in the property of the emitted laser light.

19 . The SMI sensor of claim 18 , further comprising an etch stop layer between the first set of semiconductor layers and the second set of semiconductor layers.

20 . The SMI sensor of claim 18 , wherein the VCSEL diode is configured to emit the laser light with a natural wavelength of 940 nanometers.

Assignees

• Apple Inc

Inventors

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

Classifications

• H01S5/0656

  Seeding, i.e. an additional light input is provided for controlling the laser modes, for example by back-reflecting light from an external optical component (H01S5/14, H01S5/4062 and H01S5/4006 take precedence) · CPC title

• H01S5/3095

  Tunnel junction · CPC title

• H01S5/18313 Primary

  by oxidizing at least one of the DBR layers · CPC title

• H01S5/183

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

• H01S5/3432

  the whole junction comprising only (AI)GaAs · CPC title