Optical cross-coupling mitigation systems for wavelength beam combining laser systems

• US 9,778,448 B2
• Filed: 12/10/2015
• Issued: 10/03/2017
• Est. Priority Date: 03/05/2010
• Status: Active Grant

• Current Assignee: Panasonic Corporation Of North America (Panasonic Holdings Corporation)
• Original Assignee: TeraDiode, Inc. (Panasonic Holdings Corporation)
• Inventors: Chann, Bien
• Primary Examiner(s): Pinkney, Dawayne A
• Application Number:
  US14/964,700
• Publication Number:
  US 20160161727A1
• Time in Patent Office: 663 Days
• Field of Search: 359618, 359299, 359624, 359245, 359241, 359244, 359288, 359305, 359285, 359308, 359311-312, 359290-292, 359872, 359263, 359223-224, 359318, 359649, 359846, 359129, 359496, 359631, 359629, 359634, 359636, 359638-640, 359831, 359833-834, 359630, 3593413, 35934133, 35933721, 353 31, 353 34, 353 81, 451 28, 451 41, 372 25, 372 92, 372 98, 372102
• CPC Class Codes: G02B 19/0014 at least one surface having optical power
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0057 in the form of a laser diode array, e.g. laser diode bar semiconductor laser arrays with beam combining arrangement H01S5/4012
• CPC Class Codes: G02B 2005/1804 Transmission gratings
• CPC Class Codes: G02B 27/0905 Dividing and/or superposing multiple light beams
• CPC Class Codes: G02B 27/1006 for splitting or combining different wavelengths G02B27/1086, G02B27/141 take precedence
• CPC Class Codes: G02B 27/4244 in wavelength selecting devices spectrometry G01J
• CPC Class Codes: G02B 6/0208 characterised by their structure, wavelength response G02B6/02114, G02B6/02171, G02B6/02195 take precedence; multiple layer cores or claddings G02B6/036, protective coverings G02B6/4429
• CPC Class Codes: G02B 6/14 Mode converters
• CPC Class Codes: G02B 6/262 Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements
• CPC Class Codes: G02B 6/29317 Light guides of the optical fibre type
• CPC Class Codes: G02B 6/32 having lens focusing means positioned between opposed fibre ends with lens being an integral part of the single fibre end G02B6/262
• CPC Class Codes: H01S 3/08063 Graded reflectivity, e.g. variable reflectivity mirror
• CPC Class Codes: H01S 5/141 using a wavelength selective device, e.g. a grating or etalon H01S5/146 takes precedence
• CPC Class Codes: H01S 5/4062 with an external cavity or using internal filters, e.g. Talbot filters
• CPC Class Codes: H01S 5/4068 with lateral coupling by axially offset or by merging waveguides, e.g. Y-couplers
• CPC Class Codes: H01S 5/4087 emitting more than one wavelength

Abstract

In various embodiments, wavelength beam combining laser systems incorporate optical cross-coupling mitigation systems and/or engineered partially reflective output couplers in order to reduce or substantially eliminate unwanted back-reflection of stray light.

Claims

1. A laser system comprising:

an array of beam emitters each emitting a beam having a different wavelength;

focusing optics for focusing the beams toward a dispersive element;

a dispersive element for receiving and dispersing the focused beams, thereby forming a multi-wavelength beam; and

an optical fiber for receiving the multi-wavelength beam, the optical fiber comprising (i) a core having, at an end of the optical fiber, a partially reflective outer surface for (a) receiving the multi-wavelength beam, (b) reflecting a first portion thereof back to the array of beam emitters via the dispersive element, wherein the first portion stabilizes each of the beams to its wavelength, and (c) transmitting a second portion thereof as an output beam composed of multiple wavelengths, and (ii) surrounding the core, a cladding having an outer surface (a) partially defining an end surface of the optical fiber along a diameter of the optical fiber and (b) having a reflectivity to the multi-wavelength beam of less than 1%.

2. The laser system of claim 1, wherein a portion of the core protrudes from the cladding.

3. The laser system of claim 1, wherein the optical fiber is positioned such that, at the partially reflective surface of the core, a diameter of the core is not less than a diameter of the multi-wavelength beam.

4. The laser system of claim 1, further comprising an end cap attached to the optical fiber and disposed optically upstream of the partially reflective surface of the core.

5. The laser system of claim 1, further comprising an anti-reflective coating disposed over the cladding of the optical fiber.

6. The laser system of claim 1, further comprising a mode stripper disposed around at least a portion of the core of the optical fiber.

7. The laser system of claim 1, further comprising a cross-coupling mitigation system for receiving and transmitting the multi-wavelength beam while reducing cross-coupling thereof.

8. The laser system of claim 7, wherein the partially reflecting surface of the core of the optical fiber is disposed within a Rayleigh range of the multi-wavelength beam transmitted by the cross-coupling mitigation system.

9. The laser system of claim 7, wherein at least a portion of the cross-coupling mitigation system is disposed within a Rayleigh range of the multi-wavelength beam transmitted by the dispersive element.

10. The laser system of claim 7, wherein the cross-coupling mitigation system comprises an afocal telescope.

11. The laser system of claim 7, wherein the cross-coupling mitigation system comprises a first optical element having a first focal length and a second optical element having a second focal length, the first optical element being disposed optically upstream of the second optical element.

12. The laser system of claim 11, wherein the first focal length is at least two times greater than the second focal length.

13. The laser system of claim 11, wherein the first focal length is at least seven times greater than the second focal length.

14. The laser system of claim 11, wherein each of the first and second optical elements comprises a lens.

15. The laser system of claim 11, wherein the first optical element is disposed within a Rayleigh range of the multi-wavelength beam transmitted by the dispersive element.

16. The laser system of claim 11, wherein the partially reflecting surface of the core of the optical fiber is disposed within a Rayleigh range of the multi-wavelength beam transmitted by the second optical element.

17. The laser system of claim 11, wherein an optical distance between the first and second optical elements is approximately equal to a sum of the first and second focal lengths.

18. The laser system of claim 1, wherein the partially reflective outer surface of the core has a reflectivity to the multi-wavelength beam of less than approximately 15%.

19. The laser system of claim 1, wherein the partially reflective outer surface of the core has a reflectivity to the multi-wavelength beam ranging from approximately 2% to approximately 10%.

20. The laser system of claim 1, wherein the partially reflective outer surface of the core has a reflectivity to the multi-wavelength beam ranging from approximately 4% to approximately 10%.