Emitter structures for ultra-small vertical cavity surface emitting lasers (VCSELS) and arrays incorporating the same
A laser diode includes a semiconductor structure of a lower Bragg reflector layer, an active region, and an upper Bragg reflector layer. The upper Bragg reflector layer includes a lasing aperture having an optical axis oriented perpendicular to a surface of the active region. The active region includes a first material, and the lower Bragg reflector layer includes a second material, where respective lattice structures of the first and second materials are independent of one another. Related laser arrays and methods of fabrication are also discussed.
1. A laser diode element, comprising:
a first laser diode comprising a first lower Bragg reflector layer, a first active region, and a first upper Bragg reflector layer, the first upper Bragg reflector layer comprising a lasing aperture having an optical axis oriented perpendicular to a surface of the first active region,
wherein the first active region comprises a first material, wherein the first lower Bragg reflector layer comprises a second material, wherein respective lattice structures of the first and second materials are independent of one another, and wherein the first laser diode is free of electrical contacts thereto; and
a second laser diode comprising a second active region of a third material that is configured to emit light comprising a shorter emission wavelength than that of the first material, wherein the second laser diode comprises the second active region between second upper and lower Bragg reflector layers that comprise the third material, and wherein respective lattice structures of the third material, the second material, and the first material are independent of one another and wherein the second laser diode is arranged to optically pump the first active region of the first laser diode with the light comprising the shorter emission wavelength.
2. The laser diode element of claim 1 , wherein an optical axis of a lasing aperture of the second laser diode is oriented parallel to a surface of the second active region, and further comprising:
a mirror structure arranged relative to the lasing aperture of the second laser diode to reflect the light comprising the shorter emission wavelength toward the first active region of the first laser diode.
3. The laser diode element of claim 1 , wherein an optical axis of a lasing aperture of the second laser diode is oriented perpendicular to a surface of the second active region.
4. The laser diode element of claim 1 , wherein an interface between the first lower Bragg reflector layer and the first active region is free of a seed layer for the first material.
5. A method of fabricating a Light Detection and Ranging (LIDAR) array, the method comprising:
providing a plurality of laser diodes on a non-native substrate, wherein the plurality of laser diodes comprises:
a first laser diode comprising a first lower Bragg reflector layer, a first active region, and a first upper Bragg reflector layer, the first upper Bragg reflector layer comprising a lasing aperture having an optical axis oriented perpendicular to a surface of the first active region,
wherein the first active region comprises a first material, wherein the first lower Bragg reflector layer comprises a second material, and wherein respective lattice structures of the first and second materials are independent of one another; and
a second laser diode comprising a second active region of a third material between second upper and lower Bragg reflector layers, and wherein respective lattice structures of the third material and a material of the second lower Bragg reflector layer are independent of one another, wherein the third material is configured to emit light comprising a wavelength of about 350 nanometers to about 450 nanometers.
6. The method of claim 5 , wherein the second material is a dielectric material, and wherein providing the laser diodes on the non-native substrate comprises, for the first laser diode:
forming the first lower Bragg reflector layer on the non-native substrate using a thin film deposition process;
providing the first active region on a surface of the first lower Bragg reflector layer, wherein an interface therebetween is free of a seed layer for the first material; and
forming the first upper Bragg reflector layer on the surface of the first active region using a thin film deposition process.
7. The method of claim 5 , wherein the respective lattice structures of the first and second materials are lattice mismatched.
8. The method of claim 5 , wherein the first material is different than the third material.
9. A Light Detection and Ranging (LIDAR) array, comprising:
a plurality of laser diodes arranged on a non-native substrate, wherein the plurality of laser diodes comprises:
a first laser diode comprising a first lower Bragg reflector layer, a first active region, and a first upper Bragg reflector layer, the first upper Bragg reflector layer comprising a lasing aperture thereon having an optical axis oriented perpendicular to a surface of the first active region, wherein the first active region comprises a first material, wherein the first lower Bragg reflector layer comprises a second material, and wherein respective lattice structures of the first and second materials are independent of one another; and
a second laser diode comprising a second active region of a third material between second upper and lower Bragg reflector layers, and wherein respective lattice structures of the third material and a material of the second lower Bragg reflector layer are independent of one another, wherein the third material is configured to emit light comprising a wavelength of about 350 nanometers to about 450 nanometers.
10. The LIDAR array of claim 9 , wherein the respective lattice structures of the first and second materials are lattice mismatched.
11. The LIDAR array of claim 9 , wherein the second material is a dielectric material.
12. The LIDAR array of claim 9 , wherein the first upper Bragg reflector layer comprises a dielectric material and has a lower reflectivity than the first lower Bragg reflector layer.
13. The LIDAR array of claim 9 , wherein an interface between the first lower Bragg reflector layer and the first active region is free of a seed layer for the first material.
14. The LIDAR array of claim 9 , wherein an interface between the first lower Bragg reflector layer and the first active region comprises an adhesive layer.
15. The LIDAR array of claim 9 , wherein at least one of the first lower Bragg reflector layer, the first active region, or the first upper Bragg reflector layer comprises a micro-transfer-printed layer having a residual tether portion and/or a relief feature at a periphery thereof.
16. The LIDAR array of claim 15 , wherein at least one of the residual tether portion or the relief feature comprises the first material.
17. The LIDAR array of claim 9 , wherein the first material is configured to emit light comprising a wavelength of about 1400 nanometers to about 1600 nanometers.
18. The LIDAR array of claim 9 , wherein a spacing between the first laser diode and an immediately adjacent laser diode of the plurality of laser diodes is less than about 150 micrometers, less than about 100 micrometers, or less than about 50 micrometers, and greater than about 10 micrometers.
19. The LIDAR array of claim 9 , wherein the first material is different than the third material.
20. The LIDAR array of claim 19 , wherein the first and second laser diodes are interspersed in the array among the plurality of laser diodes, or
wherein the array comprises a first area comprising a plurality of the first laser diodes and free of the second laser diodes, and a second area comprising a plurality of the second laser diodes and free of the first laser diodes.