MONOLITHIC WDM VCSELS WITH SPATIALLY VARYING GAIN PEAK AND FABRY PEROT WAVELENGTH

• US 20180175587A1
• Filed: 06/04/2015
• Published: 06/21/2018
• Est. Priority Date: 06/04/2015
• 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, Tan, Michael Renne Ty
• Granted Patent: US 10,868,407 B2
• Time in Patent Office: Days
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 33/0045 the devices being superluminescent diodes
• CPC Class Codes: H01L 33/105 with a resonant cavity structure
• CPC Class Codes: H01S 5/18305 with emission through the substrate, i.e. bottom emission
• CPC Class Codes: H01S 5/18311 using selective oxidation
• CPC Class Codes: H01S 5/18358 containing spacer layers to adjust the phase of the light wave in the cavity
• CPC Class Codes: H01S 5/3414 by vacancy induced interdiffusion
• CPC Class Codes: H01S 5/3432 the whole junction comprising only (AI)GaAs
• CPC Class Codes: H01S 5/4087 emitting more than one wavelength
• CPC Class Codes: H01S 5/423 having a vertical cavity

Abstract

An array of monolithic wavelength division multiplexing (WDM) vertical cavity surface emitting lasers (VCSELs) with spatially varying gain peak and Fabry Perot wavelength is provided. Each VCSEL includes a lower distributed Bragg reflector (DBR), a Fabry Perot tuning/current spreading layer, and a structure comprising a multiple quantum well (MQW) layer sandwiched between a lower separate confinement heterostructure (SCH) layer and an upper SCH layer. The structure is sandwiched between the DBR and the Fabry Perot tuning/current spreading layer. Each MQW experiences a different amount of quantum well intermixing and concomitantly a different wavelength shift. Each VCSEL further includes a top mirror on the Fabry Perot tuning/current spreading layer. A method is also provided for manufacturing the array.

Claims

1. An array of monolithic wavelength division multiplexing (WDM) vertical cavity surface emitting lasers (VCSELs) with spatially varying gain peak and Fabry Perot wavelength, each VCSEL including a lower distributed Bragg reflector (DBR), a Fabry Perot tuning/current spreading layer, and a structure comprising a multiple quantum well (MQW) layer sandwiched between a lower separate confinement heterostructure (SCH) layer and an upper SCH layer, the structure sandwiched between the DBR and the Fabry Perot tuning/current spreading layer, each MQW experiencing a different amount of quantum well intermixing and concomitantly a different wavelength shift,

wherein each VCSEL further includes a top mirror on the Fabry Perot tuning/current spreading layer.

2. The array of claim 1, in which the lower DBR comprises layers of GaAs and AlGaAs, the lower and upper SCH layers comprise GaAs and AlGaAs, and the MQW comprises layers of GaAs or InGaAs, and AlGaAs or InGaP or GaAsP.

3. The array of claim 1, in which the Fabry Perot tuning/current spreading layer comprises AlGaAs, GaAs, or alternating layers of AlGaAs and GaAs.

4. The array of claim 1, in which the top mirror comprises any of semiconductor Bragg reflectors, dielectric Bragg reflectors, dielectric enhanced metal hybrid mirrors, transparent conductive oxide or nitride enhanced metal hybrid mirrors, high contrast gratings, suspended reflectors, and combinations thereof.

5. The array of claim 1, in which the VCSELs are arranged in a linear fashion, each VCSEL having a larger quantum well intermixing in a particular direction, each VCSEL emitting light of a wavelength that is blue-shifted in the direction of larger quantum well intermixing.

6. The array of claim 5, in which the quantum well intermixing arises from a concentration of point defects generated by stress mismatch, with a greater number of point defects resulting in a larger quantum well intermixing.

7. The array of claim 1, in which the Fabry Perot tuning/current spreading layer has different thickness for each VCSEL in the array and in which the top mirror has the same structure or in which the Fabry Perot tuning/current spreading layer has the same thickness for each VCSEL in the array and in which the top mirror has a different structure for each VCSEL in the array or in which the Fabry Perot tuning/current spreading layer has a different thickness for each VCSEL in the array and in which the top mirror has a different structure for each VCSEL in the array.

8. The array of claim 1, further including appropriate ohmic contacts.

9. The array of claim 1, in which the VCSELs either emit light from the top side or from the bottom side.

10. A method of manufacturing an array of monolithic wavelength division multiplexed (WDM) vertical cavity surface emitting lasers (VCSELs) with spatially varying gain peak and Fabry Perot wavelength, the method including:

growing a half cavity VCSEL epitaxial wafer;

performing selective quantum well intermixing;

forming top mirrors; and

fabricating VCSELs.

11. The method of claim 10, in which growing a half cavity VCSEL epitaxial wafer comprises forming lower DBR layers on a substrate, followed by the gain media sandwiched by SCH layers, a Fabry Perot tuning/current spreading layer, and then a sacrificial layer.

12. The method of claim 11, in which performing selective quantum well intermixing comprises forming a patternable layer on the sacrificial layer, patterning the patternable layer, blanket coating the patterned layer with a stress-inducing layer, and performing rapid thermal annealing to induce quantum well mixing in a MQW layer.

13. The method of claim 12, in which the pattern selected is such that the more area covered by the patternable layer, the less stress that can be induced in the MQW layer.

14. The method of claim 12, in which forming top mirrors comprises stripping off the blanket coat, the patternable layer, and the sacrificial layer, and either progressively altering the thickness of the Fabry Perot tuning/current spreading layer across the surface, with thicker portions aligned with less intermixing in the MQW, and forming the top mirror on the Fabry Perot tuning/current spreading layer, wherein the top mirror conforms to the progressively altered Fabry Perot tuning/current spreading layer, or forming a plurality of top mirrors on the Fabry Perot tuning/current spreading layer, each top mirror to enable distinct Fabry Perot resonant wavelengths for each VCSEL.

15. The method of claim 14, in which fabricating VCSELs comprises forming the array of VCSELs, in which individual VCSELs are formed by etching and wet oxidation, followed by application of appropriate contacts.