Method and system for providing directional light sources with broad spectrum

• US 8,848,755 B1
• Filed: 12/05/2013
• Issued: 09/30/2014
• Est. Priority Date: 05/17/2010
• Status: Active Grant

• Current Assignee: Kyocera SLD Laser Incorporated (Kyocera Corporation)
• Original Assignee: Soraa Laser Diode, Inc. (Kyocera Corporation)
• Inventors: Raring, James W., Schmidt, Mathew C., Chang, Yu-Chia
• Primary Examiner(s): Nguyen, Dung
• Application Number:
  US14/097,801
• Time in Patent Office: 299 Days
• Field of Search: 372/43.01, 372/45.01, 372/50.1
• US Class Current: 372/43.01
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01L 33/0045 the devices being superluminescent diodes
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01S 2301/02 ASE (amplified spontaneous emission), noise; Reduction thereof
• CPC Class Codes: H01S 5/0427 for applying modulation to the laser
• CPC Class Codes: H01S 5/06251 Amplitude modulation
• CPC Class Codes: H01S 5/0651 Mode control
• CPC Class Codes: H01S 5/0652 Coherence lowering or collapse, e.g. multimode emission by additional input or modulation
• CPC Class Codes: H01S 5/2031 characterized by special waveguide layers, e.g. asymmetric waveguide layers or defined bandgap discontinuities
• CPC Class Codes: H01S 5/22 having a ridge or stripe structure
• CPC Class Codes: H01S 5/32025 non-polar orientation
• CPC Class Codes: H01S 5/320275 semi-polar orientation
• CPC Class Codes: H01S 5/34 comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers H01S5/36 takes precedence
• CPC Class Codes: H01S 5/3407 characterised by special barrier layers
• CPC Class Codes: H01S 5/3414 by vacancy induced interdiffusion
• CPC Class Codes: H01S 5/34333 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser
• CPC Class Codes: H01S 5/4043 with vertically stacked active layers
• CPC Class Codes: H01S 5/405 Two-dimensional arrays
• CPC Class Codes: H01S 5/4087 emitting more than one wavelength

Abstract

A system and method for providing laser diodes with broad spectrum is described. GaN-based laser diodes with broad or multi-peaked spectral output operating are obtained in various configurations by having a single laser diode device generating multiple-peak spectral outputs, operate in superluminescene mode, or by use of an RF source and/or a feedback signal. In some other embodiments, multi-peak outputs are achieved by having multiple laser devices output different lasers at different wavelengths.

Claims

1. An optical device comprising:

a gallium and nitrogen containing substrate comprising a first crystalline surface region orientation, the first crystalline surface region orientation being non-polar or semi-polar;

a current source;

a first active region comprising a barrier layer and a first emission layer, the first emission layer being characterized by a first gain peak wavelength and a first resistance, the first active region being electrically coupled to the current source, the first gain peak wavelength being based on a first amount of current received from the current source;

a second active region comprising a second emission layer, the second emission layer being characterized by a second gain peak wavelength and a second resistance, the second active region being electrically coupled to the current source, the second peak wavelength being based on a second amount of current received from the current source, a ratio between the first amount of current and the second amount of current being a function of a ratio between the first resistance and the second resistance, and wherein a difference between the first gain peak wavelength and the second gain peak wavelength is at least 1.5 nm;

a first cavity member overlying the first emission layer, the first cavity member being configured to emit radiation at a wavelength of about 430 nm to 480 nm or at a wavelength of about 505 nm to 540 nm;

a second cavity member overlying the second the emission layer; and

an optical member for combining emission from the first cavity member and from the second cavity member.

2. The device of claim 1 wherein the first resistance is associated with a size of the first cavity member.

3. The device of claim 1 wherein the difference between the first gain peak wavelength and the second gain peak wavelength is at about 5 nm.

4. The device of claim 1, wherein the active region comprises at least one quantum well and at least one barrier layer, each of the at least one quantum wells having a thickness of at least 1.5 nm, and each of the at least one barrier layers having a thickness between about 2 nm and about 22 nm.

5. The device of claim 1, wherein the first cavity member and the second cavity member each comprise a first end having an reflectivity of at least 85% and a second end having a reflectivity of 1% or less.

6. The device of claim 1, wherein the first cavity member and the second cavity member are configured to emit a directional beam of light having a spectral width of at least 3 nm.

7. The device of claim 6, wherein the spectral width is adapted to reduce speckle associated with the directional beam.

8. The device of claim 1, wherein the first cavity member and the second cavity member are configured to emit a directional beam of light having a spectral width of 4 nm to 8 nm.

9. The device of claim 1, wherein the first crystalline surface region orientation comprises a semipolar plane selected from the {20-21} plane, the {30-31} plane, the {20-2-1} plane, the {30-3-1} plane, the {11-22} plane, and an off-cut of any of the foregoing.

10. The device of claim 1, wherein the difference between the first gain peak wavelength and the second gain peak wavelength is at least 10 nm.

11. The device of claim 1, wherein the first cavity member and the second cavity member are configured to emit a directional beam of light having a spectral width greater than 1.5 nm.

12. The device of claim 1, wherein the first crystalline surface region orientation is selected from a {20-21} plane, a {20-2-1} plane, and an off-cut thereof;

and the first cavity member and the second cavity member are oriented in a projection of a c-direction.

13. The device of claim 1, wherein the first crystalline surface region orientation is selected from a {30-31} plane, a {20-21} plane, and an off-cut thereof.

14. The device of claim 1, wherein a difference between the first wavelength and the second wavelength is from 1 nm to 10 nm.