Hybrid interferometric and scatterometric sensing using in-plane sensors
An optical sensor system including a semiconductor substrate; a self-mixing interferometry (SMI) sensor formed on the semiconductor substrate and including a semiconductor laser having a resonant cavity; and an array of photodetectors formed on the semiconductor substrate. The SMI sensor is configured to generate an SMI signal responsive to a retro-reflection of electromagnetic radiation emitted by the semiconductor laser and received into the resonant cavity. The array of photodetectors is configured to generate a set of angular-resolved scatter signals responsive to a scatter of the electromagnetic radiation emitted by the semiconductor laser.
1. An optical sensor system, comprising:
a semiconductor substrate;
a self-mixing interferometry (SMI) sensor formed on the semiconductor substrate and including a semiconductor laser having a resonant cavity; and
an array of photodetectors formed on the semiconductor substrate; wherein,
the SMI sensor is configured to generate an SMI signal responsive to a retro-reflection of electromagnetic radiation emitted by the semiconductor laser and received into the resonant cavity; and
the array of photodetectors is configured to generate a set of angular-resolved scatter signals responsive to a scatter of the electromagnetic radiation emitted by the semiconductor laser.
2. The optical sensor system of claim 1 , wherein the SMI sensor and the array of photodetectors share a subset of epitaxial layers formed on the semiconductor substrate.
3. The optical sensor system of claim 1 , wherein:
a set of trenches electrically separate photodetectors in the array of photodetectors.
4. The optical sensor system of claim 3 , further comprising:
a set of cathodes for the array of photodetectors, the set of cathodes disposed in the set of trenches.
5. The optical sensor system of claim 4 , further comprising:
a set of anodes for the array of photodetectors, the set of anodes disposed on the array of photodetectors; wherein,
the set of cathodes is oriented in a first set of parallel directions;
the set of anodes is oriented in a second set of parallel directions; and
the second set of parallel directions is orthogonal to the first set of parallel directions.
6. The optical sensor system of claim 1 , further comprising:
an array of SMI sensors formed on the semiconductor substrate; wherein,
the SMI sensor is a first SMI sensor in the array of SMI sensors; and
the array of photodetectors is provided by additional SMI sensors in the array of SMI sensors.
7. An optical sensor system, comprising:
a wafer-integrated array of semiconductor devices, including,
a semiconductor laser; and
a set of resonant-cavity photodetectors (RCPDs);
an optical subsystem configured to direct a retro-reflection of electromagnetic radiation emitted by the semiconductor laser toward an RCPD in the set of RCPDs, and configured to direct an angular-resolved scatter of the electromagnetic radiation emitted by the semiconductor laser toward a subset or all RCPDs in the set of RCPDs.
8. The optical sensor system of claim 7 , wherein all of the RCPDs in the set of RCPDs are in-plane.
9. The optical sensor system of claim 7 , wherein a first RCPD is integrated or stacked with the semiconductor laser.
10. The optical sensor system of claim 7 , wherein:
the RCPD in the set of RCPDs is a first RCPD; and
the optical subsystem provides confocal imaging for,
the first RCPD; and
a second RCPD in a subset of RCPDs.
11. The optical sensor system of claim 7 , wherein:
the RCPD in the set of RCPDs is a first RCPD; and
the optical subsystem provides non-confocal imaging for,
the first RCPD; and
a second RCPD in a subset of RCPDs.
12. The optical sensor system of claim 7 , wherein the optical subsystem comprises:
a telecentric-confocal imaging system positioned apart from the wafer-integrated array of semiconductor devices in an electromagnetic radiation emission path of the semiconductor laser, and in a set of electromagnetic radiation reception paths of the set of RCPDs.
13. The optical sensor system of claim 7 , wherein the optical subsystem comprises:
a set of on-chip lenses disposed on the semiconductor laser and the set of RCPDs; and
a confocal imaging system positioned apart from the wafer-integrated array of semiconductor devices, in an electromagnetic radiation emission path of the semiconductor laser, and in a set of electromagnetic radiation reception paths of the set of RCPDs.
14. The optical sensor system of claim 13 , wherein the optical subsystem comprises:
an optical beam splitter positioned in the electromagnetic radiation emission path of the semiconductor laser.
15. The optical sensor system of claim 7 , wherein:
the wafer-integrated array of semiconductor devices is attached to a semiconductor wafer; and
the semiconductor laser is flip-chip bonded to the semiconductor wafer, over the RCPD to which the retro-reflection is directed.
16. An electronic device, comprising:
a semiconductor substrate;
a set of semiconductor devices formed on the semiconductor substrate; and
a processor configured to,
operate a first semiconductor device in the set of semiconductor devices to emit electromagnetic radiation from a resonant cavity of the first semiconductor device;
determine a set of parameters of a self-mixing interferometry (SMI) signal generated as a result of a self-mixing of electromagnetic radiation within the resonant cavity;
contemporaneously with operating the first semiconductor device, sense a scatter of the emitted electromagnetic radiation using a subset of semiconductor devices in the set of semiconductor devices; and
characterize at least one of an environment of the electronic device, or a relationship between the electronic device and the environment, using the determined set of parameters of the SMI signal and the sensed scatter.
17. The electronic device of claim 16 , wherein:
the environment of the electronic device comprises a surface; and
the processor is configured to characterize the environment of the electronic device by,
determining, using the set of parameters of the SMI signal, at least one of a speckle, a roughness, or a texture of the surface; and
determining a power spectral density of the surface using the sensed scatter.
18. The electronic device of claim 16 , wherein:
the electronic device is a wearable device;
the first semiconductor device has a different optical focus than at least a second semiconductor device in the subset of semiconductor devices;
the environment of the electronic device comprises a body part of a user of the electronic device; and
the processor is configured to characterize the environment of the electronic device by determining at least one biometric feature of the user.
19. The electronic device of claim 16 , wherein:
the environment of the electronic device comprises air; and
the processor is configured to characterize the environment of the electronic device by,
determining a particle speed using the set of parameters of the SMI signal; and
determining a particle size using the sensed scatter.
20. The electronic device of claim 16 , wherein:
the environment of the electronic device comprises a surface;
the processor is configured to characterize the relationship between the electronic device and the environment of the electronic device by,
characterizing a high speed movement of the electronic device with respect to the surface responsive to at least a sensed self-mixing; and
characterizing a low speed movement of the electronic device with respect to the surface responsive to at least the sensed scatter; and
the high speed movement and the low speed movement are distinguished by a threshold speed of movement.
21. An optical sensor system, comprising:
a semiconductor substrate;
an external photon-mixing sensor formed on the semiconductor substrate and including,
a semiconductor laser; and
a photon-mixing detector;
an array of photodetectors formed on the semiconductor substrate; wherein,
the external photon-mixing sensor is configured to generate a field-based coherent scatterometry signal responsive to a combination of electromagnetic radiation emitted by the semiconductor laser and a portion of the emitted electromagnetic radiation that is backscattered to the photo-mixing detector; and
the array of photodetectors is configured to generate a set of intensity-based scatterometry signals responsive to a backscatter of the electromagnetic radiation emitted by the semiconductor laser.
22. The optical sensor system of claim 21 , wherein the semiconductor laser, the photon-mixing detector, and the array of photodetectors share a subset of epitaxial layers formed on the semiconductor substrate.
23. The optical sensor system of claim 21 , further comprising:
an optical subsystem configured to,
direct a first portion of the electromagnetic radiation emitted by the semiconductor laser to the photon-mixing detector; and
direct a second portion of a backscatter of the emitted electromagnetic radiation to the photon-mixing detector.