Vertical cavity surface emitting laser with photodiode having reduced spontaneous emissions
View Patent ↗An optical structure that reduces the effects of spontaneous emissions from the active region of a laser. An optical structure includes optimizations to reduce the effects of spontaneous emissions. The optical structure includes a VCSEL with top and bottom DBR mirrors and an active region connected to the mirrors. The optical structure further includes a photodiode connected to the VCSEL. One or more optimizations may be included in the optical structure including optically absorbing materials, varying the geometry of the structure to change reflective angles, using optical apertures, changing the reflectivity of one or more mirrors, changing the photodiode to be more impervious to spontaneous emissions, and using ion implants to reduce photoluminescence efficiency.
1. An optical structure comprising:
a VCSEL, the VCSEL comprising:
a top DBR mirror;
an active region coupled to the top DBR mirror and configured to emit light by stimulated emission at a design wavelength; and
a bottom DBR mirror coupled to the active region, the bottom DBR mirror having more mirror periods than the top DBR mirror;
a photodiode coupled to the VCSEL, wherein the photodiode is on an opposite side of the bottom DBR from the active region;
a tunnel diode that acts as a common connection between the VCSEL and the photodiode, the tunnel diode including a doped p layer and a doped n layer; and
wherein the photodiode has a bandgap that is greater than the design wavelength, so as to reduce responsivity of the photodiode above a laser emission.
2. The optical structure of claim 1 , wherein the VCSEL comprises a mesa structure, wherein the mesa structure comprises irregularities on walls of the mesa structure.
3. The optical structure of claim 1 , further comprising an absorbing material disposed in the optical structure, the absorbing material comprising a composition configured to absorb optical emissions.
4. The optical structure of claim 1 , further comprising an optical aperture between the VCSEL and photodiode to block a portion of off-axis spontaneous emissions.
5. The optical structure of claim 1 , wherein at least one of the top DBR mirror and the bottom DBR mirror is optimized to increase the critical angle caused by an interface between the DBR mirror and the active region.
6. The optical structure of claim 1 , wherein at least one of the top DBR mirror and the bottom DBR mirror is optimized to reduce transmission of off-axis emissions at a specific angle.
7. The optical structure of claim 1 , further comprising a wide bandgap layer coupled to the photodiode on a side of the photodiode opposite the VCSEL.
8. The optical structure of claim 1 , further comprising a DBR mirror on a side of the photodiode opposite the VCSEL.
9. An optical structure comprising:
a VCSEL, the VCSEL comprising:
a top DBR mirror;
an active region coupled to the top DBR mirror; and
a bottom DBR mirror coupled to the active region;
a photodiode coupled to the VCSEL; and
a wide bandgap layer coupled to the photodiode on a side of the photodiode opposite the VCSEL, the wide bandgap layer being positioned between the photodiode and a substrate, wherein the wide bandgap layer comprises a composition that substantially prevents substrate absorption from contributing to long wavelength responsivity.
10. The optical structure of claim 9 , wherein the VCSEL comprises a mesa structure, wherein the mesa structure comprises irregularities on walls of the mesa structure.
11. The optical structure of claim 9 , further comprising an absorbing material disposed in the optical structure, the absorbing material comprising a composition configured to absorb optical emissions.
12. The optical structure of claim 9 , further comprising an optical aperture between the VCSEL and photodiode to block a portion of off-axis spontaneous emissions.
13. The optical structure of claim 9 , wherein at least one of the top DBR mirror and the bottom DBR mirror is optimized to increase the critical angle caused by an interface between the DBR mirror and the active region.
14. The optical structure of claim 9 , wherein at least one of the top DBR mirror and the bottom DBR mirror is optimized to reduce transmission of off-axis emissions at a specific angle.
15. The optical structure of claim 9 , wherein the photodiode comprises an increased bandgap to reduce responsivity of the photodiode above a laser emission.
16. The optical structure of claim 9 , further comprising a DBR mirror on a side of the photodiode opposite the VCSEL.
17. The optical structure of claim 2 , wherein the irregularities are provided by a frosted wall of a mesa structure.
18. The optical structure of claim 10 , wherein the irregularities are provided by a frosted wall of a mesa structure.
19. The optical structure of claim 9 , wherein the photodiode and the VCSEL are fabricated so as not to share a common connection.
20. An optical structure comprising:
a VCSEL, the VCSEL comprising:
a top DBR mirror;
an active region coupled to the top DBR mirror and configured to emit light by stimulated emission at a design wavelength; and
a bottom DBR mirror coupled to the active region;
a photodiode coupled to the VCSEL;
a tunnel diode that acts as a common connection between the VCSEL and the photodiode; and
a proton implant that reduces photoluminescence positioned at a periphery of the VCSEL, the proton implant extending through the top DBR mirror, the active region, and at least a portion of the bottom DBR mirror.