skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Raman Amplification with a Flying Focus

Abstract

Here, we propose a new laser amplifier scheme utilizing stimulated Raman scattering in plasma in conjunction with a "flying focus" - a chromatic focusing system combined with a chirped pump beam that provides spatiotemporal control over the pump's focal spot. Pump intensity isosurfaces are made to propagate at v=-c so as to be in sync with the injected counterpropagating seed pulse. By setting the pump intensity in the interaction region to be just about the ionization threshold of the background gas, an ionization wave is produced that travels at a fixed distance ahead of the seed. Simulations show that this will make it possible to optimize the plasma temperature and mitigate many of the issues that are known to have impacted previous Raman amplification experiments, in particular, the growth of precursors.

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1]
  1. Univ. of Rochester, Rochester, NY (United States)
Publication Date:
Research Org.:
Univ. of Rochester, Rochester, NY (United States). Lab. for Laser Energetics
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1417648
Report Number(s):
2017-179, 1366
Journal ID: ISSN 0031-9007; PRLTAO; 2017-179, 2322, 1366
Grant/Contract Number:
NA0001944; SC0016253
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 120; Journal Issue: 2; Journal ID: ISSN 0031-9007
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY

Citation Formats

Turnbull, D., Bucht, S., Davies, A., Haberberger, D., Kessler, T., Shaw, J. L., and Froula, D. H. Raman Amplification with a Flying Focus. United States: N. p., 2018. Web. doi:10.1103/PhysRevLett.120.024801.
Turnbull, D., Bucht, S., Davies, A., Haberberger, D., Kessler, T., Shaw, J. L., & Froula, D. H. Raman Amplification with a Flying Focus. United States. doi:10.1103/PhysRevLett.120.024801.
Turnbull, D., Bucht, S., Davies, A., Haberberger, D., Kessler, T., Shaw, J. L., and Froula, D. H. 2018. "Raman Amplification with a Flying Focus". United States. doi:10.1103/PhysRevLett.120.024801.
@article{osti_1417648,
title = {Raman Amplification with a Flying Focus},
author = {Turnbull, D. and Bucht, S. and Davies, A. and Haberberger, D. and Kessler, T. and Shaw, J. L. and Froula, D. H.},
abstractNote = {Here, we propose a new laser amplifier scheme utilizing stimulated Raman scattering in plasma in conjunction with a "flying focus" - a chromatic focusing system combined with a chirped pump beam that provides spatiotemporal control over the pump's focal spot. Pump intensity isosurfaces are made to propagate at v=-c so as to be in sync with the injected counterpropagating seed pulse. By setting the pump intensity in the interaction region to be just about the ionization threshold of the background gas, an ionization wave is produced that travels at a fixed distance ahead of the seed. Simulations show that this will make it possible to optimize the plasma temperature and mitigate many of the issues that are known to have impacted previous Raman amplification experiments, in particular, the growth of precursors.},
doi = {10.1103/PhysRevLett.120.024801},
journal = {Physical Review Letters},
number = 2,
volume = 120,
place = {United States},
year = 2018,
month = 1
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on January 12, 2019
Publisher's Version of Record

Save / Share:
  • The electron kinetic effects on Raman backscattering and Raman backward laser amplification were analyzed. The analysis is based on the envelope-kinetic equations of a plasma wave, which are composed of the conventional envelope equation of a fluid plasma and the kinetic term. One major goal of this paper is to close the envelope-kinetic model by analyzing the kinetic term, which was not fully covered in the previous work [M. S. Hur et al., Phys. Rev. Lett. 95, 115003 (2005)]. It was found that the closed envelope-kinetic equation in the nontrapping regime takes the same form as the envelope equation ofmore » the fluid plasma used in the three-wave model. For the closure in the trapping-dominant regime, the test particle technique is employed to calculate the kinetic term. Results from the full kinetic and test particle simulations agree well with each other, while the latter has a great advantage in computation speed. The frequency shift and resonance breaking by the trapped particles are discussed with the help of a new diagnostic inserted in the full kinetic averaged particle-in-cell code.« less
  • Stimulated Raman scattering of ethanol is investigated with picosecond laser pump pulses at 530 nm. Output of the Stokes light pulse is amplified in a traveling wave dye amplifier.
  • High-repetition-rate generation of up to 325 mJ of Raman amplified radiation near 615 cm/sup -1/ has been demonstrated in CO/sub 2/-pumped para-H/sub 2/ using a low-power, microwave-shifted CF/sub 4/ laser as an input Stokes seed source. Experiments were limited to 200 Hz, but single-shot Schlieren measurements indicate that our flowing room-temperature 44-pass Raman converter should be capable of the design goal of 1 kHz. Strong conversion was achieved even with no flow at 100 Hz. Details of the overall system design, experimental parameters, and present system limitations are discussed. 19 references, 8 figures.
  • The processes of generation of Stokes radiation during superregenerative SRS amplification in compressed hydrogen have been studied experimentally and theoretically. The optimum shifts of Stokes pulses relative to pumping pulses during nonstationary and transient SRS amplification have been determined. The determining role of SRS focusing in the formation of spatial-coherence functions of amplified Stokes radiation has been established. It is shown that Stokes radiation can reproduce the spatial structure of the pumping field during noncollinear propagation in a multimode Raman-active waveguide. Under optimum amplification conditions in a waveguide with a Fresnel number of approx.100, a nearly 50% efficiency of pumpingmore » energy conversion to a highly coherent Stokes beam was obtained.« less