Facet on a gallium and nitrogen containing laser diode

• US 9,343,871 B1
• Filed: 03/25/2013
• Issued: 05/17/2016
• Est. Priority Date: 04/05/2012
• Status: Active Grant

• Current Assignee: Kyocera SLD Laser Incorporated (Kyocera Corporation)
• Original Assignee: Soraa Laser Diode, Inc. (Kyocera Corporation)
• Inventors: Raring, James W., Huang, Hua
• Primary Examiner(s): Zhang, Yuanda
• Assistant Examiner(s): CARTER, MICHAEL W
• Application Number:
  US13/850,187
• Time in Patent Office: 1,149 Days
• Field of Search: 372/49.01
• US Class Current: 1/1
• CPC Class Codes: H01S 5/0203 Etching
• CPC Class Codes: H01S 5/028 Coatings ; Treatment of the laser facets, e.g. etching, passivation layers or reflecting layers
• CPC Class Codes: H01S 5/0282 Passivation layers or treatments
• CPC Class Codes: H01S 5/0285 Coatings with a controllable reflectivity
• CPC Class Codes: H01S 5/0287 Facet reflectivity
• CPC Class Codes: H01S 5/2009 by using electron barrier layers
• CPC Class Codes: H01S 5/22 having a ridge or stripe structure
• CPC Class Codes: H01S 5/2201 in a specific crystallographic orientation
• CPC Class Codes: H01S 5/32025 non-polar orientation
• CPC Class Codes: H01S 5/320275 semi-polar orientation
• CPC Class Codes: H01S 5/34333 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser

Abstract

Nonpolar or semipolar laser diode technology incorporating etched facet mirror formation and conventional optical coating layer techniques for reflectivity modification to enable a method for ultra-high catastrophic optical mirror damage thresholds for high power laser diodes are disclosed.

Claims

1. A gallium and nitrogen containing laser device, the device comprising:

a gallium and nitrogen containing surface having either a nonpolar orientation or a semipolar orientation;

a cladding region overlying the gallium and nitrogen containing surface, the cladding region having an AlN mol fraction of less than about 2%;

a cavity region overlying the gallium and nitrogen containing surface and configured in alignment in substantially a c-direction or a projection of the c-direction, the cavity region being characterized by a first end and a second end;

the first end comprising a first etched facet;

the second end comprising a second etched facet wherein the first etched facet and the second etched facet are at an angle of between 87 degrees and 93 degrees from the gallium and nitrogen containing surface, and the first etched facet and the second etched facet have a root mean square roughness of 50 nm or less;

a first optical coating overlying the first etched facet, wherein the first optical coating is configured to increase a reflectivity of the first etched facet to a laser beam generated in the cavity region, the first optical coating comprising a first layer of SiO₂ and a second layer of tantalum pentoxide;

wherein the first layer of SiO₂ directly contacts the entire first etched facet, and the second layer of tantalum pentoxide covers the entire first layer; and

a second optical coating overlying the second etched facet, wherein the second optical coating is configured to reduce a reflectivity of the second etched facet to the laser beam generated in the cavity region, the second optical coating comprising a first layer of SiO₂ and a second layer of Al₂O₃, wherein the first layer of SiO₂ directly contacts the entire second etched facet and is configured as a passivation layer, and the second layer of Al₂O₃ covers the entire first layer and is configured to reduce the reflectivity of the second etched facet, the second optical coating having a substantially uniform thickness across the second etched facet.

2. The device of claim 1, wherein the nonpolar orientation or the semipolar orientation of the gallium and nitrogen containing surface comprises an m-plane, a (30-31) plane, a (20-21) plane, a (30-32) plane, a (30-3-1) plane, a (20-2-1) plane, a (30-3-2) plane, or an offcut of within +/−

5 degrees of any of these planes toward an a-direction or a c-direction.

3. The device of claim 1, wherein the first optical coating is provided by a method selected from electron-beam deposition, thermal evaporation, PECVD, sputtering, and a combination of any of the foregoing.

4. The device of claim 1, wherein the first etched facet and the second etched facet are formed using a CAIBE process.

5. The device of claim 1, wherein the first etched facet and the second etched facet are formed using an etching process selected from reactive ion etching, inductively coupled plasma etching, and chemical assisted ion beam etching.

6. The device of claim 1, wherein the device comprises an output cavity width of greater than about 3 μ

m and less than about 25 μ

m and is operable at an output power over 1 W, or wherein the device comprises an output cavity width of greater than about 3 μ

m and less than about 25 μ

m and is operable at an output power over 2 W, or wherein the device comprises an output cavity width of greater than about 3 μ

m and less than about 35 μ

m and is operable at an output power over 3 W, or wherein the device comprises an output cavity width of greater than about 3 μ

m and less than about 35 μ

m and is operable at an output power over 4.5 W, or wherein the device comprises an output cavity width of greater than about 3 μ

m and less than about 50 μ

m and is operable at an output power over 3 W.

7. The device of claim 1, wherein the device is substantially free from catastrophic optical mirror damage (COMD) for power levels greater than 100 mW per micron of output cavity width, 200 mW per micron of output cavity width, or 400 mW per micron of output cavity width.

8. The device of claim 1, wherein the device is operable at a wavelength from 430 nm to 480 nm.

9. The device of claim 1, wherein the device is operable at a wavelength from 480 nm to 535 nm.

10. The device of claim 1, wherein the device is operable at a wavelength from 390 nm to 430 nm.

11. A gallium and nitrogen containing laser device, the device comprising:

a gallium and nitrogen containing surface having either a nonpolar orientation or a semipolar orientation;

a cladding region overlying the gallium and nitrogen containing surface;

the cladding region having an AlN mol fraction of less than about 2%;

a cavity region overlying the cladding region and configured in alignment in substantially a c-direction or a projection of the c-direction, the cavity region being characterized by a first end and a second end;

the first end comprising a first etched facet;

the second end comprising a second etched facet;

wherein the first etched facet and the second etched facet are at an angle of between 87 degrees and 93 degrees from the gallium and nitrogen containing surface, and the first etched facet and the second etched facet have a root mean square roughness of 50 nm or less;

a first optical coating overlying the first etched facet, wherein the first optical coating is configured to increase a reflectivity of the first etched facet to a laser beam generated in the cavity region, the first optical coating comprising a first layer of SiO₂ and a second layer of tantalum pentoxide;

wherein the first layer of SiO₂ directly contacts the entire first etched facet, and the second layer of tantalum pentoxide covers the entire first layer;

a second optical coating overlying the second etched facet, wherein the second optical coating is configured to reduce a reflectivity of the second etched facet to the laser beam generated in the cavity region, the second optical coating comprising a first layer of SiO₂ and a second layer of Al₂O₃, wherein the first layer of SiO₂ directly contacts the entire second etched facet and is configured as a passivation layer, and the second layer of Al₂O₃ covers the entire first layer and is configured to reduce the reflectivity of the second etched facet, the second optical coating having a substantially uniform thickness across the second etched facet; and

an optical power density characterizing the laser device, the laser device being substantially free from catastrophic optical mirror damage (COMD) related failure.

12. The device of claim 11, wherein the nonpolar orientation or the semipolar orientation of the gallium and nitrogen containing surface comprises an m-plane, a (30-31) plane, a (20-21) plane, a (30-32) plane, a (30-3-1) plane, a (20-2-1) plane, a (30-3-2) plane, or an offcut of within +/−

5 degrees of any of these planes toward an a-direction or a c-direction.

13. The device of claim 11, wherein the first etched facet and the second etched facet are formed using an etching process selected from reactive ion etching, inductively coupled plasma etching, and chemical assisted ion beam etching.

14. The device of claim 11, wherein the device is substantially free from COMD for power levels greater than 100 mW per micron of output cavity width, 200 mW per micron of output cavity width, or 400 mW per micron of output cavity width.

15. A method of fabricating a gallium and nitrogen containing laser device, the method comprising:

providing a gallium and nitrogen containing surface having either a nonpolar orientation or a semipolar orientation;

forming a cladding region overlying the gallium and nitrogen containing surface, the cladding region having an AlN mol fraction of less than about 2%;

forming a cavity region overlying the gallium and nitrogen containing surface and configured in alignment in substantially a c-direction or a projection of the c-direction, the cavity region being characterized by a first end and a second end;

etching the first end of the cavity region to form a first etched facet;

etching the second end of the cavity region to form a second etched facet wherein the first etched facet and the second etched facet are formed using an etching process selected from reactive ion etching, inductively coupled plasma etching, and chemical assisted ion beam etching;

wherein the first etched facet and the second etched facet are at an angle of between 87 degrees and 93 degrees from the gallium and nitrogen containing surface after etching, and the first etched facet and the second etched facet have a root mean square roughness of 50 nm or less;

forming a first optical coating overlying the first etched facet by electron-beam deposition, wherein the first optical coating is configured to increase a reflectivity of the first etched facet to a laser beam generated in the cavity region, the first optical coating comprising a first layer of SiO₂ and a second layer of tantalum pentoxide;

wherein the first layer of SiO₂ directly contacts the entire first etched facet, and the second layer of tantalum pentoxide covers the entire first layer;

forming a second optical coating overlying the second etched facet by electron-beam deposition, wherein the second optical coating layer is configured to reduce a reflectivity of the second facet to the laser beam generated in the cavity region, the second optical coating comprising the first layer of SiO₂ and a second layer of Al₂O₃, wherein the first layer of SiO₂ directly contacts the entire second etched facet and is configured as a passivation layer, and the second layer of Al₂O₃ covers the entire first layer and is configured to reduce the reflectivity of the second etched facet, the second optical coating having a substantially uniform thickness across the second facet;

wherein the first layer of SiO₂ is blanket deposited on the first etched facet and the second etched facet after etching; and

operating the laser device at an optical power density of greater than 400 mW per micron of output cavity width without catastrophic optical mirror damage (COMD) related failure.

16. The method of claim 15, wherein the nonpolar orientation or the semipolar orientation of the gallium and nitrogen containing surface comprises an m-plane, a (30-31) plane, a (20-21) plane, a (30-32) plane, a (30-3-1) plane, a (20-2-1) plane, a (30-3-2) plane, or an offcut of within +/−

5 degrees of any of these planes toward an a-direction or a c-direction.