Phased laser array with tailored spectral and coherence properties

• US 7,916,762 B2
• Filed: 05/27/2009
• Issued: 03/29/2011
• Est. Priority Date: 05/27/2008
• Status: Active Grant

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Inventors: Beach, Raymond J, Dawson, Jay W, Messerly, Michael J
• Primary Examiner(s): Harvey; Minsun
• Assistant Examiner(s): Nguyen; Tuan N.
• Application Number:
  US12/472,564
• Publication Number:
  US 20090296747A1
• Time in Patent Office: 671 Days
• Field of Search: 372/23, 372/29.01, 372/25, 372/28
• US Class Current: 372/18
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 3/0064 Anti-reflection devices, e.g. optical isolaters absorbing layers for marking or protecting purposes in laser working B23K26/50; magneto-optical non-reciprocal devices G02F1/093, G02F1/0955
• CPC Class Codes: H01S 3/067 Fibre lasers
• CPC Class Codes: H01S 3/094003 the pumped medium being a fibre
• CPC Class Codes: H01S 3/10092 Coherent seed, e.g. injection locking
• CPC Class Codes: H01S 3/1067 using pressure or deformation
• CPC Class Codes: H01S 3/1306 Stabilisation of the amplitude
• CPC Class Codes: H01S 3/1618 ytterbium
• CPC Class Codes: H01S 3/235 Regenerative amplifiers
• CPC Class Codes: H01S 3/2383 Parallel arrangements

Abstract

Architectures for coherently combining an array of fiber-based lasers are provided. By matching their lengths to within a few integer multiples of a wavelength, the spatial and temporal properties of a single large laser are replicated, while extending the average or peak pulsed power limit.

Claims

1. A fiber optic laser array, comprising:

a plurality of fiber optics, wherein each fiber optic of said plurality of fiber optics comprises an active laser gain medium;

means for controlling the length of said each fiber optic;

means for optically pumping said active laser gain medium of said each fiber optic to produce a plurality of laser beams; and

means for phase locking said plurality of laser beams, wherein said each laser beam of said plurality of laser beams comprises a frequency bandwidth, means for controlling the length is configured to match the transit time of light through said each fiber to within the reciprocal of said bandwidth, wherein said means for controlling comprises a system for producing radio-frequency (RF) radiation, wherein said system is configured to (i) transmit said RF radiation through said each fiber and (ii) measure the phase of said RF radiation, wherein said each laser beam of said plurality of laser beams comprises a frequency bandwidth in excess of 1 GHz.

2. The array of claim 1, wherein said means for controlling the length is configured to the control the absolute length of said each fiber optic to one another to be within a few wavelengths of light.

3. The array of claim 2, wherein said means for controlling comprises a mechanism for altering each length of said lengths.

4. The array of claim 3, wherein said mechanism comprises a PZT.

5. The array of claim 1, wherein said means for controlling the length is configured to match the transit time of light through said each fiber to within 10 ns.

6. The array of claim 1, wherein said means for controlling the length includes an interferometer.

7. The array of claim 1, wherein said each laser beam of said plurality of laser beams comprises a frequency bandwidth in excess of 100 GHz.

8. A method, comprising:

providing a plurality of fiber optics, wherein each fiber optic of said plurality of fiber optics comprises an active laser gain medium;

controlling the length of said each fiber optic;

optically pumping said active laser gain medium of said each fiber optic to produce a plurality of laser beams; and

phase locking said plurality of laser beams, wherein said each laser beam of said plurality of laser beams comprises a frequency bandwidth, wherein the step of controlling the length matches the transit time of light through said each fiber to within the reciprocal of said bandwidth, wherein the step of controlling transmits radio-frequency (RF) radiation through said each fiber and measures the phase of said RF radiation, and wherein said each laser beam of said plurality of laser beams comprises a frequency bandwidth in excess of 1 GHz.

9. The method of claim 8, wherein the step of controlling the length controls the absolute length of said each fiber optic to one another to be within a few wavelengths of light.

10. The method of claim 9, wherein the step of controlling includes altering each length of said lengths.

11. The method of claim 10, wherein the step of controlling uses a PZT for altering each length of said lengths.

12. The method of claim 8, wherein the step of controlling the length matches the transit time of light through said each fiber to within 10 ns.

13. The method of claim 8, wherein the step of controlling the length uses an interferometer.

14. The method of claim 8, wherein said each laser beam of said plurality of laser beams comprises a frequency bandwidth in excess of 100 GHz.