Dense wavelength beam combining with variable feedback control

Patent metadata

Field	Value
Publication number	US-9711950-B2
Application number	US-201514711579-A
Country	US
Kind code	B2
Filing date	May 13, 2015
Priority date	May 13, 2015
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

An external cavity laser apparatus according to an embodiment of the invention is provided. The external cavity laser apparatus includes a plurality of beam emitters that collectively emit a plurality of emitted beams that each includes a primary component emitted beam. A first reflective element is configured to reflect the plurality of primary component emitted beams and a first polarizing optic disposed in the optical path of the plurality of primary component emitted beams is configured to rotate a polarization of each primary component emitted beam to produce a first rotated primary component beam having a first linear polarization and a second rotated primary component beam having a second linear polarization. A polarized beam splitter is configured to direct first feedback system output component beams into an output beam, and to direct second feedback system output component beams to the plurality of beam emitters as feedback beams.

First claim

The invention claimed is:

1. An external cavity laser apparatus comprising:
a plurality of beam emitters that collectively emit a plurality of emitted beams each including a primary component emitted beam and having a wavelength;
an angular dispersive optic disposed in the optical path of the plurality of primary component emitted beams and configured to combine the plurality of primary component emitted beams into a combined input beam, the combined input beam including a plurality of component input beams;
a first polarizing optic disposed in the optical path of the combined input beam and configured to:
rotate a polarization of each of the plurality of component beams of the combined input beam to produce a rotated combined input beam, the rotated combined input beam including a plurality of rotated component input beams, and
rotate a polarization of a reflection of each of the plurality of rotated component input beams of the rotated combined input beam to produce a first combined feedback system output beam having a first linear polarization and a second combined feedback system output beam having a second linear polarization, wherein the first combined feedback system output beam includes a plurality of first feedback system output component beams and wherein the second combined feedback system output beam includes a plurality of second feedback system output component beams; and

a polarized beam splitter configured to:
direct the first combined feedback system output beam as a single combined output beam, and
direct the second combined feedback system output beam to the angular dispersive optic as a first single combined feedback beam,

the angular dispersive optic being further configured to:
split the first single combined feedback beam into a plurality of first feedback beams, and
direct the plurality of first feedback beams back to the plurality of beam emitters to stabilize the wavelengths of the plurality of emitted beams.

2. The apparatus of claim 1 , wherein the polarized beam splitter is further configured to direct the combined input beam to the first polarizing optic.

3. The apparatus of claim 1 , wherein each of the plurality of emitted beams additionally includes a secondary component emitted beam.

4. The apparatus of claim 3 , further comprising a reflective element;
wherein the polarized beam splitter is further configured to direct the plurality of secondary component emitted beams to the reflective element.

5. The apparatus of claim 1 , wherein the dispersive optic is a polarization insensitive grating.

6. The apparatus of claim 1 , further comprising a first reflective element configured to reflect the rotated combined input beam to produce a reflected rotated combined input beam, wherein the reflected rotated combined input beam includes the reflection of each of the plurality of rotated component input beams.

7. The apparatus of claim 6 , wherein a second reflective element is configured to direct a reflection of a plurality of secondary component emitted beams as a plurality of components of a third feedback system output beam to the polarized beam splitter, and
wherein the polarized beam splitter is further configured to direct the plurality of components of the third feedback system output beam to the plurality of beam emitters.

8. The apparatus of claim 6 , wherein a second reflective element is configured to direct a reflection of a plurality of secondary component emitted beams as a plurality of components of a third feedback system output beam to the polarized beam splitter, and
wherein the polarized beam splitter is configured to direct the plurality of components of the third feedback system output beams as components of the single combined output beam.

9. The apparatus of claim 1 , wherein the angular dispersive optic has a wavelength-dependent angular dispersion function, and
wherein the angular dispersive optic is configured to combine the plurality of primary component emitted beams into a combined input beam by being configured to impart a wavelength-dependent angular spectrum determined by the wavelength-dependent angular dispersion function on the plurality of primary component emitted beams.

10. The apparatus of claim 9 , further comprising a first position-to-angle transform optic disposed in an optical path between the plurality of beam emitters and the angular dispersive optic and configured to impart upon each of the plurality of emitted beams an angle of incidence with respect to the angular dispersive optic.

11. The apparatus of claim 10 , further comprising a second polarizing optic disposed between the plurality of beam emitters and the angular dispersive optic and configured to rotate a polarization of each of the plurality of emitted beams.

12. The apparatus of claim 11 , wherein the second polarizing optic is a half wave plate.

13. The apparatus of claim 9 , further comprising a spatial filtering assembly disposed in an optical path of one of the combined input beam and the rotated combined input beam and configured to transmit only component beams that correspond to a portion of the wavelength-dependent angular spectrum.

14. The apparatus of claim 13 , wherein the spatial filtering assembly comprises:
a second position-to-angle transform optic;
a third position-to-angle transform optic; and
an aperture disposed between the second position-to-angle transform optic and the third position-to-angle transform optic.

15. The apparatus of claim 14 , wherein the array is formed from one of a plurality of diode bars configured in a vertical stack, a plurality of diode bars configured in a horizontal stack, or two-dimensional array of diode bars.

16. The apparatus of claim 1 , wherein the plurality of beam emitters is one of a plurality of diode beam emitters arranged in a bar and a plurality of diode beam emitters arranged in an array.

17. The apparatus of claim 1 , wherein the first polarizing optic is a quarter wave plate.

18. The apparatus of claim 1 , wherein the second combined feedback system output beam has an optical power that is less than about 20% of an optical power of the plurality of emitted beams.

19. The system of claim 1 , wherein the single combined output beam is a multi-wavelength beam that includes a plurality of spatially and directionally overlapped individual single wavelength beams.

20. The system of claim 1 , wherein the first single combined feedback beam is a multi-wavelength beam that includes a plurality of spatially and directionally overlapped individual single wavelength beams.

21. The system of claim 1 , wherein the angular dispersive optic is configured to direct each of the plurality of first feedback beams back to an emitter of the plurality of beam emitters that emitted one of the plurality of emitted beams to which it corresponds.

22. A method for stabilizing the wavelengths of a plurality of emitted beams collectively emitted by a plurality of emitters, each of the plurality of emitted beams including a primary component emitted beam, the method comprising:
emitting, by the plurality of emitters, the plurality of emitted beams collectively including the plurality of primary component emitted beams;
combining, by an angular dispersive optic disposed in the optical path of the plurality of primary component emitted beams, the plurality of primary component emitted beams into a combined input beam, the combined input beam including a plurality of component input beams;
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Assignees

• TRUMPF Laser GmbH (TLS)
• Trumpf Laser Gmbh

Inventors

• Zimer Hagen
• Killi Alexander
• Ried Steffen
• Nagel Simon
• Ginter Markus

Classifications

• H01S3/08054

  Passive cavity elements acting on the polarization, e.g. a polarizer for branching or walk-off compensation (quarter-wave plates in a Q-switch laser H01S3/1124, H01S3/115) · CPC title

• H01S5/141

  using a wavelength selective device, e.g. a grating or etalon (H01S5/146 takes precedence) · CPC title

• H01S5/4062

  with an external cavity or using internal filters, e.g. Talbot filters · CPC title

• H01S3/10061

  Polarization control · CPC title

• H01S5/4012 Primary

  Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms · CPC title