Scaling high-energy pulsed solid-state lasers to high average power

Patent metadata

Field	Value
Publication number	US-11296478-B2
Application number	US-201916678063-A
Country	US
Kind code	B2
Filing date	Nov 8, 2019
Priority date	May 8, 2017
Publication date	Apr 5, 2022
Grant date	Apr 5, 2022

Abstract

Techniques are provided for scaling the average power of high-energy solid-state lasers to high values of average output power while maintaining high efficiency. An exemplary technique combines a gas-cooled-slab amplifier architecture with a pattern of amplifier pumping and extraction in which pumping is continuous and in which only a small fraction of the energy stored in the amplifier is extracted on any one pulse. Efficient operation is achieved by propagating many pulses through the amplifier during each period equal to the fluorescence decay time of the gain medium, so that the preponderance of the energy cycled through the upper laser level decays through extraction by the amplified pulses rather than through fluorescence decay.

First claim

We claim:

1. A method, comprising:
providing a gas cooled solid-state laser gain medium;
continuously optically pumping said gain medium for a period of time to produce excited state ions; and
producing amplified pulses by directing a plurality of pulses to be amplified through said gain medium;
wherein said laser gain medium has a fluorescence decay time; and
wherein the plurality of pulses to be amplified are directed through said laser gain medium in less time than the fluorescence decay time of said laser gain medium.

2. The method of claim 1 , wherein said gain medium comprises at least one slab.

3. The method of claim 1 , wherein said gain medium has fluorescence lifetime that is sufficiently long that at least 10% of the stored energy that remains in the gain medium after any one amplified pulse of the amplified pulses carries over to the next amplified pulse of the amplified pulses.

4. The method of claim 1 , further comprising:
a plurality of optics positioned to receive said plurality of pulses to be amplified;
wherein said gain medium has a saturation fluence that is high enough to make it impossible to achieve at least a 20% extraction efficiency without operating at a fluence above the lowest damage threshold of said plurality of optics when only one pulse is propagated through the plurality of optics during the fluorescence decay time of the laser gain medium.

5. The method of claim 1 , wherein the operating fluence of said gain medium is lower than its damage fluence, even when its saturation fluence is greater than the damage fluence.

6. The method of claim 1 , further comprising a plurality of optics positioned to receive said plurality of pulses to be amplified, wherein said gain medium comprises a gain spectra that is sufficiently broad such that said amplified pulses can be optically compressed to sub-ps duration and wherein said gain medium comprises a saturation fluence that is high enough to make it impossible to achieve at least a 20% extraction efficiency without operating at a fluence above the lowest damage threshold of said plurality of optics, when only one pulse is propagated through the plurality of optics during the fluorescence decay time of the laser gain medium.

7. The method of claim 1 , wherein the step of continuously optically pumping said gain medium is carried out with at least one laser diode.

8. The method of claim 1 , wherein the extraction efficiency for any one amplified pulse of the amplified pulses is no more than a few percent and the stored energy extracted by the amplified pulses is greater than the energy lost due to fluorescence decay.

9. The method of claim 1 , wherein said gain medium comprises a plurality of gas-cooled slabs.

10. The method of claim 1 , wherein said gain medium comprises at least one rare-earth dopant.

11. The method of claim 1 , wherein said gain medium comprises slabs of at least one anisotropic gain material mounted so that two or more optical axes of said slabs interact with the amplified pulses to increase the gain bandwidth and wherein the order in which said slabs are mounted is selected to minimize the required doping of said gain medium and/or to minimize the pump power required in the step of continuously optically pumping said gain medium.

12. An apparatus, comprising:
a gas cooled solid-state laser gain medium;
means for continuously optically pumping said gain medium for a period of time to produce excited state ions; and
means for producing amplified pulses by directing a plurality of pulses to be amplified through said gain medium;
wherein the laser gain medium has a fluorescence decay time; and
wherein the apparatus is configured to direct the plurality of pulses to be amplified through said laser gain medium in less time than the fluorescence decay time of the laser gain medium.

13. The apparatus of claim 12 , wherein said gain medium comprises at least one slab.

14. The apparatus of claim 12 , wherein said gain medium has a fluorescence lifetime that is sufficiently long that at least 10% of the stored energy that remains in the gain medium after any one amplified pulse of the amplified pulses carries over to the next amplified pulse of the amplified pulses.

15. The apparatus of claim 12 , further comprising:
a plurality of optics positioned to receive said plurality of pulses to be amplified;
wherein said gain medium has a saturation fluence that is high enough to make it impossible to achieve at least a 20% extraction efficiency without operating at a fluence above the lowest damage threshold of said plurality of optics when only one pulse is propagated through the plurality of optics during the fluorescence decay time of the laser gain medium.

16. The apparatus of claim 12 , wherein the operating fluence of said gain medium is lower than its damage fluence, even when its saturation fluence is greater than the damage fluence.

17. The apparatus of claim 12 , further comprising a plurality of optics positioned to receive said plurality of pulses to be amplified, wherein said gain medium comprises a gain spectra that is sufficiently broad such that said amplified pulses comprise sub-ps pulses and wherein said gain medium comprises a saturation fluence that is high enough to make it impossible to achieve at least a 20% extraction efficiency without operating at a fluence above the lowest damage threshold of said plurality of optics, when only one pulse is propagated through the plurality of optics during the fluorescence decay time of the laser gain medium.

18. The apparatus of claim 12 , wherein the step of continuously optically pumping said gain medium is carried out with at least one laser diode.

19. The apparatus of claim 12 , wherein the extraction efficiency for any one amplified pulse of the amplified pulses is no more than a few percent and the stored energy extracted by the amplified pulses is greater than the energy lost due to fluorescence decay.

20. The apparatus of claim 12 , wherein said gain medium comprises a plurality of gas-cooled slabs.

21. The apparatus of claim 12 , wherein said gain medium comprises at least one rare-earth dopant.

22. The apparatus of claim 12 , wherein said gain medium comprises slabs of at least one anisotropic gain material mounted so that two or more optical axes of said slabs interact with the amplified pulses to increase the gain bandwidth and wherein the order in which said slabs are mounted is selected to minimize the required doping of said gain medium and/or to minimize the pump power required in when said gain medium is continuously optically pumped.

Assignees

• L Livermore Nat Security Llc

Inventors

• Erlandson Alvin C
• Bayramian Andrew J
• Haefner Constantin L
• Siders Craig W
• Galvin Thomas C
• Spinka Thomas M

Classifications

• H01S3/025

  of solid state lasers, e.g. housings or mountings · CPC title

• H01S3/0404 Primary

  Air- or gas cooling, e.g. by dry nitrogen · CPC title

• H01S3/2333

  Double-pass amplifiers · CPC title

• H01S3/10013

  by controlling the temperature of the active medium · CPC title

• H01S3/22

  Gases · CPC title