Bottom emitting vertical-cavity surface-emitting lasers

• US 10,290,996 B1
• Filed: 04/25/2018
• Issued: 05/14/2019
• Est. Priority Date: 04/25/2018
• Status: Active Grant

• Current Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Original Assignee: Hewlett Packard Enterprise Development LP (Hewlett-Packard Enterprise Company)
• Inventors: Mathai, Sagi Varghese, Cheung, Stanley, Sorin, Wayne V., Tan, Michael Renne Ty
• Primary Examiner(s): Park, Kinam
• Application Number:
  US15/962,649
• Time in Patent Office: 384 Days
• CPC Class Codes: H01S 2301/176 Specific passivation layers on surfaces other than the emission facet
• CPC Class Codes: H01S 5/0234 Up-side down mountings, e.g. Flip-chip, epi-side down mountings or junction down mountings
• CPC Class Codes: H01S 5/02476 Heat spreaders, i.e. improving heat flow between laser chip and heat dissipating elements
• CPC Class Codes: H01S 5/183 having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]
• 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 5/18311 using selective oxidation
• CPC Class Codes: H01S 5/18313 by oxidizing at least one of the DBR layers
• CPC Class Codes: H01S 5/18341 Intra-cavity contacts
• CPC Class Codes: H01S 5/18369 based on dielectric materials
• CPC Class Codes: H01S 5/18375 based on metal reflectors
• CPC Class Codes: H01S 5/18377 comprising layers of different kind of materials, e.g. combinations of semiconducting with dielectric or metallic layers
• CPC Class Codes: H01S 5/18386 Details of the emission surface for influencing the near- or far-field, e.g. a grating on the surface
• CPC Class Codes: H01S 5/18388 Lenses
• CPC Class Codes: H01S 5/187 using Bragg reflection

Abstract

A bottom-emitting vertical-cavity surface-emitting laser (VCSEL) structure includes a first substrate permitting the passage of light therethrough, an n-doped distributed Bragg reflector (nDBR), a p-doped distributed Bragg reflector (pDBR), one or more active layers, at least one of a high contrast grating mirror and a dielectric-enhanced metal mirror, and a plurality of layers, where the VCSEL structure is configured to be flip chipped to a second substrate. The pDBR and the nDBR define a laser cavity extending vertically therebetween and containing the one or more active layers. The at least one of a high contrast grating mirror and a dielectric-enhanced metal mirror may be disposed over the pDBR. The plurality of layers may be disposed over the at least one of the high contrast grating mirror and the dielectric-enhanced metal mirror to optically and hermetically seal the laser cavity.

Claims

1. A bottom-emitting vertical-cavity surface-emitting laser (VCSEL) structure comprising:

a first substrate permitting the passage of light therethrough;

an n-doped distributed Bragg reflector (nDBR) disposed on the first substrate and including a first plurality of layers of semiconductor material;

a p-doped distributed Bragg reflector (pDBR) having a second plurality of layers of semiconductor material, the pDBR and the nDBR defining a laser cavity extending vertically therebetween;

one or more active layers disposed in the laser cavity between the nDBR and the pDBR;

at least one of a high contrast grating mirror and a dielectric-enhanced metal mirror disposed over the pDBR; and

a third plurality of layers disposed over the at least one of the high contrast grating mirror and the dielectric-enhanced metal mirror, the third plurality of layers including a trace layer, an insulating layer, and a thermal conductive layer disposed between the trace layer and the insulating layer, each of the third plurality of layers configured to optically and hermetically seal the laser cavity from an environment external of the bottom-emitting VCSEL structure, and the thermal conducting layer further configured to extract heat from the laser cavity,

wherein the VCSEL structure is configured to be flip chipped to a second substrate.

2. The bottom-emitting VCSEL structure of claim 1, further comprising:

a current spreading layer disposed on the pDBR; and

the high contrast grating mirror disposed on the current spreading layer.

3. The bottom-emitting VCSEL structure of claim 2, further comprising the dielectric-enhanced metal mirror disposed on the high contrast grating mirror.

4. The bottom-emitting VCSEL structure of claim 1, further comprising:

a current spreading layer disposed on the pDBR; and

the dielectric-enhanced metal mirror disposed on the current spreading layer.

5. The bottom-emitting VCSEL structure of claim 1, wherein the one or more active layers include multiple quantum well (MQW) gain media.

6. The bottom-emitting VCSEL structure of claim 1, wherein the first substrate defines a lens through which the light is permitted to pass.

7. The bottom-emitting VCSEL structure of claim 1, wherein the second plurality of layers of semiconductor material includes pairs of aluminum gallium arsenide (AlGaAs) layers, each pair of AlGaAs layers having a first AlGaAs layer and a second AlGaAs layer, the first AlGaAs layer having a different concentration of aluminum than the second AlGaAs layer, and the first AlGaAs layers and the second AlGaAs layers being arranged in an alternating sequence within the pDBR.

8. The bottom-emitting VCSEL structure of claim 7, wherein the second plurality of layers of semiconductor material includes twenty or fewer pairs of AlGaAs layers.

9. The bottom-emitting VCSEL structure of claim 1, wherein the first plurality of layers of semiconductor material includes pairs of aluminum gallium arsenide (AlGaAs) layers, each pair of AlGaAs layers having a first AlGaAs layer and a second AlGaAs layer, the first AlGaAs layer having a different concentration of aluminum than the second AlGaAs layer, and the first AlGaAs layers and the second AlGaAs layers being arranged in an alternating sequence within the nDBR.

10. The bottom-emitting VCSEL structure of claim 1, further comprising an oxidized layer disposed over the one or more active layers and defining an oxide aperture to contain a current flowing therethrough.

11. A bottom-emitting vertical-cavity surface-emitting laser (VCSEL) structure comprising:

a first substrate permitting the passage of light therethrough;

a first mirror portion disposed on the first substrate and including a first plurality of layers of semiconductor material;

a second mirror portion including a second plurality of layers of semiconductor material, the first mirror portion and the second mirror portion defining a cavity extending vertically therebetween, and the second mirror portion further including

an oxidized layer defining an oxide aperture to contain a current flowing therethrough; and

at least one of a high contrast grating mirror and a dielectric-enhanced metal mirror disposed over the oxidized layer;

an active region disposed within the cavity;

a third plurality of layers disposed over the second mirror portion to optically and hermetically seal the cavity from an environment external of the bottom-emitting VCSEL structure; and

a polyimide layer surrounding the second mirror portion and coupling the one or more layers of the third plurality of layers, the first mirror portion, and the second mirror portion,

wherein the VCSEL structure is configured to be flip chipped to a second substrate.

12. The bottom-emitting VCSEL structure of claim 11, wherein:

the first mirror portion is an n-doped distributed Bragg reflector (nDBR);

the second mirror portion includes a p-doped distributed Bragg reflector (pDBR); and

each of the first plurality of layers and the second plurality of layers includes pairs of aluminum gallium arsenide (AlGaAs) layers, each pair of AlGaAs layers having a first AlGaAs layer and a second AlGaAs layer, the first AlGaAs layer having a different concentration of aluminum than the second AlGaAs layer, and the first AlGaAs layers and the second AlGaAs layers being arranged in an alternating sequence within the nDBR and the pDBR.

13. The bottom-emitting VCSEL structure of claim 11, wherein the active region includes multiple quantum well (MQW) gain media.

14. The bottom-emitting VCSEL structure of claim 11, wherein the second mirror portion further comprises a current spreading layer, and the high contrast grating mirror is disposed on the current spreading layer.

15. The bottom-emitting VCSEL structure of claim 14, further comprising the dielectric-enhanced metal mirror disposed on the high contrast grating mirror.

16. The bottom-emitting VCSEL structure of claim 11, wherein the second mirror portion further comprises a current spreading layer, and the dielectric-enhanced metal mirror is disposed on the current spreading layer.

17. A bottom-emitting vertical-cavity surface-emitting laser (VCSEL) structure comprising:

a first substrate permitting the passage of light therethrough;

an n-doped distributed Bragg reflector (nDBR) disposed on the first substrate and including a first plurality of layers of semiconductor material;

a p-doped distributed Bragg reflector (pDBR) having a second plurality of layers of semiconductor material, the pDBR and the nDBR defining a laser cavity extending vertically therebetween;

one or more active layers disposed in the laser cavity between the nDBR and the pDBR;

an oxidized layer disposed over the one or more active layers and defining an oxide aperture to contain a current flowing therethrough;

a current spreading layer disposed over the pDBR;

at least one of a high contrast grating mirror and a dielectric-enhanced metal mirror disposed over the current spreading layer;

a third plurality of layers disposed over the at least one of the high contrast grating mirror and the dielectric-enhanced metal mirror to optically and hermetically seal the laser cavity from an environment external of the bottom-emitting VCSEL structure;

a plurality of contact rings to electrically couple a trace layer of the third plurality of layers with the pDBR and the nDBR; and

a plurality of solder bumps disposed on each of the trace layer and an insulating layer of the third plurality of layers to flip chip and electrically couple the bottom-emitting VCSEL structure to a second substrate.

18. The bottom-emitting VCSEL structure of claim 17, further comprising the high contrast grating mirror disposed on the current spreading layer.

19. The bottom-emitting VCSEL structure of claim 18, further comprising the dielectric-enhanced metal mirror disposed on the high contrast grating mirror.

20. The bottom-emitting VCSEL structure of claim 17, further comprising the dielectric-enhanced metal mirror disposed on the current spreading layer.