Laser-based devices utilizing improved self-mix sensing
A device has a laser unit, which includes: a top-side p-type DBR region; which is on top of and in direct touch with an active region; which is on top of and in direct touch with a bottom-side n-type Distributed Bragg Reflector (DBR) region; which is on top of a n-type substrate. The laser unit further includes a voltage measurement anode touching or being in proximity to a top surface of the active region; and a voltage measurement cathode touching or being in proximity to a bottom surface of the active region. The voltage between the voltage measurement anode and the voltage measurement cathode is directly measured; and is utilized for determining characteristics of a laser self-mix signal of the laser unit, without having or using a monitor photo-diode.
1. A device comprising:
a self-mix laser unit comprising:
an active region having a first side and a second, opposite, side;
a p-type Distributed Bragg Reflector (DBR) region, which is in direct touch with said first side of said active region;
an n-type Distributed Bragg Reflector (DBR) region, which is in direct touch with said second side of said active region;
an n-type substrate;
a voltage measurement anode that is either touching or is in proximity to said first side of said active region;
a voltage measurement cathode that is either touching or is in proximity to said second side of said active region;
an active-voltage measurement unit, which is directly connected to said voltage measurement anode and to said voltage measurement cathode,
wherein said active-voltage measurement unit is to directly measure a voltage between said voltage measurement anode and said voltage measurement cathode;
wherein said self-mix laser unit transmits an outgoing laser beam towards a remote target, and receives an optical signal reflected back from said remote target;
wherein the outgoing laser beam and the reflected optical signal perform self-mix in said self-mix laser unit and produce a laser self-mix signal in said self-mix laser unit;
a laser self-mix signal characterizer module, to determine one or more characteristics of said laser self-mix signal based on the voltage that is measured between said voltage measurement anode and said voltage measurement cathode.
2. The device of claim 1 ,
wherein the voltage measurement anode is located at a stepped recess of said p-type DBR region.
3. The device of claim 1 ,
wherein the voltage measurement cathode is located at a stepped recess of said active region.
4. The device of claim 1 ,
wherein the voltage measurement anode is located at a stepped recess of said p-type DBR region; and wherein the voltage measurement cathode is located at a stepped recess of said active region.
5. The device of claim 1 ,
wherein the voltage measurement anode is generally-parallel to a surface of said active region;
wherein the voltage measurement cathode is generally-parallel to the surface of said active region.
6. The device of claim 1 ,
wherein D 1 denotes a distance between the voltage measurement anode and a top surface of said active region;
wherein D 2 denotes a distance between the voltage measurement anode and a top-surface of the p-DBR region;
wherein D 3 denotes a distance between the voltage measurement cathode and a bottom-surface of the active region;
wherein D 4 denotes a distance between the voltage measurement cathode and a bottom-surface of the n-DBR region;
wherein the ratio of D 1 to D 1 +D 2 is smaller than 0.25;
wherein the ratio of D 3 to D 3 +D 4 is smaller than 0.25.
7. The device of claim 1 ,
wherein D 1 denotes a distance between the voltage measurement anode and a top surface of said active region;
wherein D 2 denotes a distance between the voltage measurement anode and a top-surface of the p-DBR region;
wherein D 3 denotes a distance between the voltage measurement cathode and a bottom-surface of the active region;
wherein D 4 denotes a distance between the voltage measurement cathode and a bottom-surface of the n-DBR region;
wherein the ratio of D 1 to D 1 +D 2 is smaller than 0.15;
wherein the ratio of D 3 to D 3 +D 4 is smaller than 0.15.
8. The device of claim 1 ,
wherein the p-DBR region is formed of a particular number of layers which is between 24 layers and 36 layers;
wherein each layer of the p-DBR region has a layer thickness which is 1/(4 ni) of a wavelength of a laser beam generated by said laser unit,
wherein ni is the index of refraction of each layer.
9. The device of claim 1 ,
wherein the n-DBR region is formed of a particular number of layers which is between 24 layers and 36 layers;
wherein each layer of the n-DBR region has a layer thickness which is 1/(4 ni) of a wavelength of a laser beam generated by said laser unit,
wherein ni is the index of refraction of each layer.
10. The device of claim 1 ,
wherein D 1 denotes a distance between the voltage measurement anode and a top surface of said active region;
wherein each i-layer of the p-DBR region has a layer thickness L i which is 1/(4 ni) of a wavelength of a laser beam generated by said laser unit;
wherein D 1 has a value selected from the group consisting of:
0,
L 1 ,
L 1 +L 2 ,
L 1 +L 2 +L 3 ,
L 1 +L 2 +L 3 +L 4 ,
L 1 +L 2 +L 3 +L 4 +L 5 ,
L 1 +L 2 +L 3 +L 4 +L 5 +L 6 .
11. The device of claim 1 ,
wherein D 3 denotes a distance between the voltage measurement cathode and a bottom-surface of the active region;
wherein each i-layer of the n-DBR region has a layer thickness L i which is 1/(4 ni) of a wavelength of a laser beam generated by said laser unit;
wherein D 3 has a value selected from the group consisting of:
0,
L 1 ,
L 1 +L 2 ,
L 1 +L 2 +L 3 ,
L 1 +L 2 +L 3 +L 4 ,
L 1 +L 2 +L 3 +L 4 +L 5 ,
L 1 +L 2 +L 3 +L 4 +L 5 +L 6 .
12. The device of claim 1 ,
wherein D 1 denotes a distance between the voltage measurement anode and a top surface of said active region;
wherein D 1 has a value that is greater than 179 nanometers and is smaller than 301 nanometers.
13. The device of claim 1 ,
wherein D 3 denotes a distance between the voltage measurement cathode and a bottom-surface of the active region;
wherein D 3 has a value that is greater than 179 nanometers and is smaller than 301 nanometers.
14. The device of claim 1 ,
wherein the self-mix laser unit excludes a Monitor Photo-Diode (MPD),
wherein said laser self-mix signal characterizer module determines the one or more characteristics of said laser self-mix signal without receiving any signal from any MPD.
15. The device of claim 1 ,
wherein the device is a laser-based microphone.
16. The device of claim 1 ,
wherein the device is a hybrid optical-and-acoustic sensor which comprises a laser-based microphone and an acoustic microphone.
17. A device comprising:
a self-mix laser unit comprising:
an active region having a first side and a second, opposite, side;
a p-type Distributed Bragg Reflector (DBR) region, which is in direct touch with said first side of said active region;
an n-type Distributed Bragg Reflector (DBR) region, which is in direct touch with said second side of said active region;
an n-type substrate;
a voltage measurement anode that is either touching or is in proximity to said first side of said active region;
a voltage measurement cathode that is either touching or is in proximity to said second side of said active region;
wherein the voltage measurement anode is slanted and is non-parallel relative to a surface of said active region;
wherein the voltage measurement cathode is slanted and is non-parallel relative to said surface of said active region.
18. The device of claim 17 ,
wherein the device is a laser-based microphone.
19. The device of claim 17 ,
wherein the device is a hybrid optical-and-acoustic sensor which comprises a laser-based microphone and an acoustic microphone.
20. A multiple Vertical Cavity Surface Emitting Laser (multiple-VCSEL) system comprising:
a first VCSEL self-mix laser unit, which is monolithically co-located with a second VCSEL self-mix laser unit;
(I) wherein the first VCSEL self-mix laser unit comprises:
a first-VCSEL active region, having a first side and a second, opposite, side;
a first-VCSEL p-type Distributed Bragg Reflector (DBR) region, which is in direct touch with said first side of said first-VCSEL active region;
a cross-VCSEL unified n-type Distributed Bragg Reflector (DBR) region, which is in direct touch with said second side of said first-VCSEL active region;
a cross-VCSEL unified n-type substrate;
a first voltage measurement anode that is either touching or is in proximity to the first side of said first-VCSEL active region;
a cross-VCSEL voltage measurement cathode touching the second side of said cross-VCSEL unified n-type substrate;
(II) wherein the second VCSEL self-mix laser unit comprises:
a second-VCSEL active region, having a first side and a second, opposite, side;
a second-VCSEL p-type DBR region, which is in direct touch with said first side of said second-VCSEL active region;
said cross-VCSEL unified n-type DBR region, which is in direct touch with said second side of said second-VCSEL active region;
said cross-VCSEL unified n-type substrate;
a second voltage measurement anode that is either touching or is in proximity to the first side of said second-VCSEL active region;
said cross-VCSEL voltage measurement cathode that is either touching or is in proximity to the second side of said cross-VCSEL unified n-type substrate;
wherein said multiple-VCSEL system comprises:
a first-VCSEL active-voltage measurement unit, which is directly connected to said first voltage measurement anode and to said cross-VCSEL voltage measurement cathode,
wherein said first-VCSEL active-voltage measurement unit is to directly measure a first voltage between said first voltage measurement anode and said cross-VCSEL voltage measurement cathode;
a second-VCSEL active-voltage measurement unit, which is directly connected to said second voltage measurement anode and to said cross-VCSEL voltage measurement cathode,
wherein said second-VCSEL active-voltage measurement unit is to directly measure a second voltage between said second voltage measurement anode and said cross-VCSEL voltage measurement cathode.
21. The multiple-VCSEL system of claim 20 ,
wherein the first VCSEL self-mix laser unit transmits a first outgoing laser beam towards a remote target, and receives a first optical feedback signal that is reflected back from said remote target;
wherein the first outgoing laser beam and the first reflected optical feedback signal perform self-mix in said first VCSEL laser unit and produce a first-VCSEL self-mix signal in said first VCSEL self-mix laser unit;
wherein the first VCSEL self-mix laser unit further comprises: a first-VCSEL laser self-mix signal characterizer module, to determine one or more characteristics of said first-VCSEL self-mix signal based on the voltage that is measured between said first-VCSEL voltage measurement anode and said cross-VCSEL voltage measurement cathode;
wherein the second VCSEL self-mix laser unit transmits a second outgoing laser beam towards said remote target, and receives a second optical feedback signal that is reflected back from said remote target;
wherein the second outgoing laser beam and the second reflected optical feedback signal perform self-mix in said second VCSEL self-mix laser unit and produce a second-VCSEL self-mix signal in said second VCSEL self-mix laser unit;
wherein the second VCSEL self-mix laser unit further comprises: a second-VCSEL laser self-mix signal characterizer module, to determine one or more characteristics of said second-VCSEL self-mix signal based on the voltage that is measured between said second-VCSEL voltage measurement anode and said cross-VCSEL voltage measurement cathode.
22. The multiple-VCSEL system of claim 21 ,
wherein the system excludes any Monitor Photo-Diode (MPD) units,
wherein said first-VCSEL laser self-mix signal characterizer module determines the one or more characteristics of said first-VCSEL laser self-mix signal without receiving any signal from any MPD;
wherein said second-VCSEL laser self-mix signal characterizer module determines the one or more characteristics of said second-VCSEL laser self-mix signal without receiving any signal from any MPD.
23. The multiple-VCSEL system of claim 20 ,
wherein said multiple-VCSEL system is a laser-based microphone.
24. The multiple-VCSEL system of claim 20 ,
wherein said multiple-VCSEL system is a hybrid optical-and-acoustic sensor which comprises a laser-based microphone and an acoustic microphone.