SUB-WAVELENGTH GRATING INTEGRATED VCSEL

• US 20100316079A1
• Filed: 06/07/2010
• Published: 12/16/2010
• Est. Priority Date: 01/14/2004
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Mateus, Carlos Fernando Rondina, Zhou, Ye, Huang, Michael Chung-Yi, Chang-Hasnain, Connie J.
• Granted Patent: US 8,059,690 B2
• Time in Patent Office: Days
• US Class Current: 372/45.01
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G02B 26/0808 by means of one or more diffracting elements
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 27/42 Diffraction optics , i.e. systems including a diffractive element being designed for providing a diffractive effectG02B27/60 takes precedence
• CPC Class Codes: G02B 27/4255 for alignment or positioning purposes optical displacement encoding scales G01D5/347
• CPC Class Codes: G02B 27/4261 having a diffractive element with major polarization dependent properties
• CPC Class Codes: G02B 5/0816 Multilayer mirrors, i.e. having two or more reflecting layers G02B5/0883, G02B5/0891 take precedence
• CPC Class Codes: G02B 5/1809 with pitch less than or comparable to the wavelength
• CPC Class Codes: G02B 5/1861 Reflection gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence
• CPC Class Codes: H01S 5/0655 Single transverse or lateral mode emission
• CPC Class Codes: H01S 5/18319 comprising a periodical structure in lateral directions
• CPC Class Codes: H01S 5/1835 Non-circular mesa
• CPC Class Codes: H01S 5/18355 having a defined polarisation
• CPC Class Codes: H01S 5/18366 Membrane DBR, i.e. a movable DBR on top of the VCSEL
• CPC Class Codes: H01S 5/187 using Bragg reflection

Abstract

A vertical cavity surface emitting laser (VCSEL) is described using a sub-wavelength grating (SWG) structure that has a very broad reflection spectrum and very high reflectivity. The grating comprises segments of high and low refractive index materials with an index differential between the high and low index materials. By way of example, a SWG reflective structure is disposed over a low index cavity region and above another reflective layer (either SWG or DBR). In one embodiment, the SWG structure is movable, such as according to MEMS techniques, in relation to the opposing reflector to provide wavelength selective tuning. The SWG-VCSEL design is scalable to form the optical cavities for a range of SWG-VCSELs at different wavelengths, and wavelength ranges.

Claims

1. A vertical-cavity surface emitting laser device, comprising:

a first sub-wavelength grating (SWG) reflector configured with a plurality of periodically spaced segments of high refractive index material over a layer of low refractive index material forming a first reflector;

a first distributed Bragg reflector (DBR) configured with a plurality of alternating layers of high and low refractive index materials;

said first distributed Bragg reflector retained substantially parallel to said first reflector to form a second reflector;

a resonant cavity of predetermined depth formed between said first reflector and said second reflector;

means for optical confinement between said first and second reflectors; and

means for current injection.

2. The vertical-cavity surface emitting laser device as recited in claim 1, further comprising means for changing the distance between said first sub-wavelength grating and said first distributed Bragg reflector to form a wavelength variable vertical-cavity surface emitting laser device.

3. The vertical-cavity surface emitting laser device as recited in claim 1, further comprising at least one reflective protective layer between said first sub-wavelength grating reflector and said resonant cavity.

4. The vertical-cavity surface emitting laser device as recited in claim 3, wherein said reflective protective layer comprises a second distributed Bragg reflector comprising fewer layers than said first distributed Bragg reflector.

5. The vertical-cavity surface emitting laser device as recited in claim 3, wherein said reflective protective layer comprises a second distributed Bragg reflector which is p-doped in the case of the first distributed Bragg reflector being n-doped, or n-doped in the case of the first distributed Bragg reflector being p-doped.

6. The vertical-cavity surface emitting laser device as recited in claim 1, wherein said means for current injection comprises a first contact electrode coupled to said second distributed Bragg reflector or said first sub-wavelength grating, and a second contact electrode coupled to said first distributed Bragg reflector.

7. The vertical-cavity surface emitting laser device as recited in claim 1, wherein said means for optical confinement comprises an in-plane aperture through a vertical portion of said resonant cavity configured to provide optical confinement.

8. The vertical-cavity surface emitting laser device as recited in claim 1, further comprising a plurality of semiconductor quantum structures within an active region that forms said resonant cavity, or within said segments of high refractive index material, or within a combination of said resonant cavity and said segments of high refractive index material.

9. The vertical-cavity surface emitting laser device as recited in claim 8, wherein said quantum structures are selected in any combination from the group of quantum elements consisting essentially of quantum wells, quantum wires and quantum dots.

10. A vertical-cavity surface emitting laser device, comprising:

a first sub-wavelength grating (SWG) reflector configured with a plurality of periodically spaced segments of high refractive index material over a layer of low refractive index material forming a first reflector;

a first distributed Bragg reflector (DBR) configured with a plurality of alternating layers of high and low refractive index materials;

said first distributed Bragg reflector retained substantially parallel to said first reflector to form a second reflector;

a resonant cavity of predetermined depth formed between said first reflector and said second reflector;

means for optical confinement between said first and second reflectors;

means for current injection; and

a plurality of semiconductor quantum structures disposed within an active region of said resonant cavity, or within said segments of high refractive index material, or within a combination of said resonant cavity and said segments of high refractive index material.

11. The vertical-cavity surface emitting laser device as recited in claim 10, further comprising means for changing the distance between said first sub-wavelength grating and said first distributed Bragg reflector to form a wavelength variable vertical-cavity surface emitting laser device.

12. The vertical-cavity surface emitting laser device as recited in claim 10, further comprising at least one reflective protective layer between said first sub-wavelength grating reflector and said resonant cavity.

13. The vertical-cavity surface emitting laser device as recited in claim 12, wherein said reflective protective layer comprises a second distributed Bragg reflector comprising fewer layers than said first distributed Bragg reflector.

14. The vertical-cavity surface emitting laser device as recited in claim 12, wherein said reflective protective layer comprises a second distributed Bragg reflector which is p-doped in the case of the first distributed Bragg reflector being n-doped, or n-doped in the case of the first distributed Bragg reflector being p-doped.

15. The vertical-cavity surface emitting laser device as recited in claim 10, wherein said means for current injection comprises a first contact electrode coupled to said second distributed Bragg reflector or said first sub-wavelength grating, and a second contact electrode coupled to said first distributed Bragg reflector.

16. The vertical-cavity surface emitting laser device as recited in claim 10, wherein said means for optical confinement comprises an in-plane aperture through a vertical portion of said resonant cavity configured to provide optical confinement.

17. The vertical-cavity surface emitting laser device as recited in claim 10, wherein said quantum structures are selected in any combination from the group of quantum elements consisting essentially of quantum wells, quantum wires and quantum dots.

18. A vertical-cavity surface emitting laser device, comprising:

a first sub-wavelength grating (SWG) reflector configured with a plurality of periodically spaced segments of high refractive index material over a layer of low refractive index material forming a first reflector;

a first distributed Bragg reflector (DBR) configured with a plurality of alternating layers of high and low refractive index materials;

said first distributed Bragg reflector retained substantially parallel to said first reflector to form a second reflector;

a resonant cavity of predetermined depth formed between said first reflector and said second reflector;

means for optical confinement between said first and second reflectors;

means for current injection; and

means for changing the distance between said first sub-wavelength grating and said first distributed Bragg reflector to form a wavelength variable vertical-cavity surface emitting laser device.

19. The vertical-cavity surface emitting laser device as recited in claim 18, further comprising a plurality of semiconductor quantum structures within an active region that forms said resonant cavity, or within said segments of high refractive index material, or within a combination of said resonant cavity and said segments of high refractive index material.

20. The vertical-cavity surface emitting laser device as recited in claim 19, wherein said quantum structures are selected in any combination from the group of quantum elements consisting essentially of quantum wells, quantum wires and quantum dots.