Low voltage multi-junction vertical cavity surface emitting laser

• US 6,936,486 B2
• Filed: 11/19/2002
• Issued: 08/30/2005
• Est. Priority Date: 11/19/2002
• Status: Expired due to Fees

• Current Assignee: Viavi Solutions, Inc. (Lumentum Holdings Inc.)
• Original Assignee: Viavi Solutions, Inc. (Lumentum Holdings Inc.)
• Inventors: Liu, Guoli, Cheng, Julian, Murty, Medicharla Venkata Ramana, Shieh, Chan-Long
• Primary Examiner(s): Picardat, Kevin M.
• Application Number:
  US10/299,387
• Publication Number:
  US 20040095978A1
• Time in Patent Office: 1,015 Days
• Field of Search: 438/22, 438/31, 438/39, 438/41, 438/42, 438/44, 438/46, 438/47, 372/43, 372/44, 372/45, 372/46, 372/50, 372/96
• US Class Current: 438/22
• CPC Class Codes: H01S 5/0216 using an intermediate compound, e.g. a glue or solder
• CPC Class Codes: H01S 5/0217 Removal of the substrate
• CPC Class Codes: H01S 5/0427 for applying modulation to the laser
• CPC Class Codes: H01S 5/18305 with emission through the substrate, i.e. bottom emission
• CPC Class Codes: H01S 5/18308 having a special structure for lateral current or light confinement
• CPC Class Codes: H01S 5/18316 Airgap confined
• CPC Class Codes: H01S 5/18341 Intra-cavity contacts
• CPC Class Codes: H01S 5/18369 based on dielectric materials
• CPC Class Codes: H01S 5/3235 emitting light at a wavelength longer than 1000 nm, e.g. InP-based 1300 nm and 1500 nm lasers
• CPC Class Codes: H01S 5/426 Vertically stacked cavities

Abstract

An optical device with a wavelength of operation, the device comprising a light emitting region which emits light at the wavelength of operation, the light emitting region including an active region and a contact region of a first conductivity type and a second conductivity type wherein the light emitting region is positioned within an optical gain cavity which includes a mirror and an opposed mirror and a substrate solder bonded using a bonding layer to at least one of the mirror and the opposed mirror.

Claims

1. A method of fabricating an optical device with a wavelength of operation, the method comprising the steps of:

providing a first substrate;

epitaxially growing a light emitting region which emits light at the wavelength of operation, the light emitting region being positioned on the first substrate wherein the light emitting region includes an active region and a contact region of a first conductivity type and a second conductivity type such that the light emitting region is sandwiched between contact regions of opposite conductivity types;

epitaxially growing a first stack of alternate layers of a first material with a first index of refraction and a second material with a second index of refraction positioned on the light emitting region wherein the first index of refraction is substantially different from the second index of refraction so that the first stack of alternate layers forms a first mirror;

solder bonding a second substrate to the first stack of alternate layers;

removing the first substrate to substantially expose the light emitting region; and

epitaxially growing a second stack of alternate layers of a third material with a third index of refraction and a fourth material with a fourth index of refraction positioned on the light emitting region wherein the third index of refraction is substantially different from the fourth index of refraction so that the second stack of alternate layers forms a second mirror.

2. A method as claimed in claim 1 wherein the step of epitaxially growing the light emitting region further includes the step of forming the active region such that the active region is positioned between a first cladding region and a second cladding region.

3. A method as claimed in claim 1 wherein the first substrate includes at least one of indium phosphide (InP) and another suitable substrate material which is lattice matched to subsequent layers grown thereon.

4. A method as claimed in claim 1 wherein the second substrate includes at least one of indium phosphide (InP), gallium arsenide (GaAs), silicon (Si), and another suitable substrate material which has suitable thermally conductive and supporting properties.

5. A method as claimed in claim 1 wherein at least one of the first and second stack of alternate layers include an alloy of AlGaAs and wherein each layer of the first, second, third, and fourth material has a thickness approximately equal to one quarter of the wavelength of operation.

6. A method as claimed in claim 1 wherein at least one of the first and second stack of alternate layers include alternate layers of silicon oxide (SiO) and titanium oxide (TiO) and wherein each layer in the alternate layers has a thickness approximately equal to one quarter of the wavelength of operation.

7. A method as claimed in claim 1 wherein at least one of the first and second stack of alternate layers include alternate layers of magnesium fluoride (MgF) and zinc selenide (ZnSe) and wherein each layer in the alternate layers has a thickness approximately equal to one quarter of the wavelength of operation.

8. A method as claimed in claim 2 wherein the active region includes a plurality of quantum structures with a bandgap wavelength substantially equal to the wavelength of operation, wherein each of the plurality of quantum structures includes at least one of quantum wells, quantum dots, and another similar quantum structure which enhances light emission.

9. A method as claimed in claim 8 wherein each quantum structure of the plurality of quantum structures is positioned between quantum barrier layers wherein each quantum barrier layer has a bandgap wavelength smaller than the bandgap wavelength of the quantum structures.

10. A method as claimed in claim 9 wherein each adjacent quantum structure of the plurality of quantum structures in the active region is spaced apart such that constructive interference occurs between each adjacent quantum structure.

11. A method as claimed in claim 8 wherein each quantum structure contains one or more barrier layers including alloys of InAlAs to provide improved carrier confinement for the double heterostructure junction.

12. A method as claimed in claim 1 wherein at least one of the first and second stack of alternate layers include alloys of AlGaAs which are continuously graded in composition to form continuously graded heterointerfaces.

13. A method as claimed in claim 2 wherein a portion of at least one of the first and second cladding regions is isolation implanted with at least one of hydrogen ions (H⁺), helium ions (He⁺ or He⁺⁺), and another suitable ion to form a light path channel which extends form the first stack of alternate layers to the second stack of alternate layers.

14. A method as claimed in claim 2 wherein the step of epitaxially growing the light emitting region includes the step of forming the cladding region adjacent to the second stack of alternate layers with a plurality of index guide regions to form a light path channel which extends from the first stack of alternate layers to the second stack of alternate layers, wherein the at least one index guide region is positioned adjacent to the second stack of alternate layers.

15. A method as claimed in claim 1 wherein the wavelength of operation is within a range given approximately from 1.2 μ

m to 1.6 μ

m.

16. A method as claimed in claim 1 wherein the step of solder bonding includes using a bonding layer which includes at least one of gold/silicon (Au/Si), gold/tin (Au/Sn), gold/germanium (Au/Ge), or another suitable solder material with a desired property for adhesion.

17. A method as claimed in claim 16 wherein the bonding layer includes a window to allow substantial light emission through the second substrate.

18. A method as claimed in claim 1 wherein at least one contact region of at least one of the first and second conductivity type includes at least two layers of the same conductivity type and a substantially different doping concentration.

19. A method as claimed in claim 2 further including the step of etching a trench through the light emitting region to provide substantial current confinement.

20. A method as claimed in claim 19 further including the step of forming an undercut trench adjacent to the trench and substantially extending into at least one of the active region, the first cladding region, and the second cladding region to provide substantial current confinement.

21. A method of fabricating a multijunction laser with a wavelength of operation, the method comprising the steps of:

providing a first substrate;

epitaxially growing a light emitting region which emits light at the wavelength of operation, the light emitting region being positioned on the first substrate wherein the light emitting region includes a plurality of active regions with a plurality of quantum structure layers each sandwiched between cladding regions and wherein each of the plurality of active regions is separated by alternate contact regions of a first conductivity type and a second conductivity type wherein the first conductivity type is opposite in conductivity to the second conductivity type;

epitaxially growing a first stack of alternate layers of a first material with a first index of refraction and a second material with a second index of refraction positioned on the light emitting region wherein the first index of refraction is substantially different from the second index of refraction so that the first stack of alternate layers forms a first mirror;

solder bonding a second substrate to the first stack of alternate layers;

removing the first substrate to substantially expose the at least one light emitting region; and

epitaxially growing a second stack of alternate layers of a third material with a third index of refraction and a fourth material with a fourth index of refraction positioned on the light emitting region wherein the third index of refraction is substantially different from the fourth index of refraction so that the second stack of alternate layers forms a second mirror.

22. A method as claimed in claim 21 wherein at least one of the first and second stack of alternate layers include alternate layers of silicon oxide (SiO) and titanium oxide (TiO) and wherein each layer in the alternate layers has a thickness approximately equal to one quarter of the wavelength of operation.

23. A method as claimed in claim 21 wherein at least one of the first and second stack of alternate layers include alternate layers of magnesium fluoride (MgF) and zinc selenide (ZnSe) and wherein each layer in the alternate layers has a thickness approximately equal to one quarter of the wavelength of operation.

24. A method as claimed in claim 21 wherein each quantum structure layer is positioned between a quantum barrier layer wherein each quantum barrier layer has a bandgap wavelength smaller than a bandgap wavelength of the quantum structure layers.

25. A method as claimed in claim 21 wherein the step of solder bonding includes using a bonding layer which includes at least one of gold/silicon (Au/Si), gold/tin (Au/Sn), gold/germanium (Au/Ge), or another suitable solder material with a desired property for adhesion.

26. A method as claimed in claim 21 wherein each adjacent active region in the plurality of active regions includes a substantially equal current path such that each active region emits a substantially equal amount of light.

27. A method as claimed in claim 21 wherein each contact region in the alternate contact regions includes a substantially equal current path between each adjacent contact region.

28. A method of modulating a multifunction laser with a wavelength of operation, the method comprising the steps of:

epitaxially growing a light emitting region positioned within an optical gain cavity which includes a mirror and an opposed mirror, wherein the light emitting region emits light at the wavelength of operation and includes a plurality of active regions wherein each of the plurality of active regions is separated by alternate contact regions of a first conductivity type and a second conductivity type;

forming a suitable electrical contact to each alternate contact region of the first and second conductivity types;

electrically connecting a direct current power source and one of an alternating current power source and an alternating current power return to each contact region of the first conductivity type; and

electrically connecting a direct current power return to each contact region of the second conductivity type.

29. A method as claimed in claim 28 wherein at least one contact region includes at least two layers of the same conductivity type and substantially different doping concentrations.

30. A method as claimed in claim 28 wherein each adjacent active region in the plurality of active regions includes a substantially equal current path such that each active region emits a substantially equal amount of light.

31. A method as claimed in claim 28 wherein each contact region in the alternate contact regions includes a substantially equal current path between each adjacent contact region.