Study of self-diffraction from laser generated plasma gratings in the nanosecond regime

Journal Article · 29 July 2019 · Physics of Plasmas

DOI: https://doi.org/10.1063/1.5087734 · OSTI ID:1638009

Schrauth, S. E. ^[1]; Colaitis, A.  ^[1]; Luthi, R. L. ^[1]; Plummer, R. C. W. ^[1]; Hollingsworth, W. G. ^[1]; Carr, C. W. ^[1]; Norton, M. A. ^[1]; Wallace, R. J. ^[1]; Hamza, A. V. ^[1]; MacGowan, B. J. ^[1]; Shaw, M. J. ^[1]; Spaeth, M. L. ^[1]; Manes, K. R. ^[1]; Michel, P. ^[1]; Di Nicola, J.-M. ^[1]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

We investigate the formation and diffraction efficiency of plasma gratings generated by the interference of two laser beams crossing at a small angle on the surface of a planar aluminum target. Such gratings were observed during National Ignition Facility experiments with the ratio of energy in the first-order to zeroth order of ≈60%. Recently, additional experiments were performed on the Optical Sciences Laser. These experiments with only two interfering beams showed high normalized energy (ratio of energy in diffracted order to zeroth order) of approximately 10% and 3% at the first and second diffracted order locations, respectively, for intensities less than 1012 W/cm2. The existence of the higher-orders is the characteristic of diffraction from gratings in the Raman-Nath as opposed to the Bragg regime. In addition, we show conical diffraction from the generated plasma grating. Using numerical simulations, we explore the large difference in diffraction efficiency observed in these two experiments and highlight the role of plasma temperature and density scale length. The simulations suggest a modulation depth of the plasma grating refractive index ranging from 1.77×10-4 to 3.5×10-2. These results are relevant to Inertial Confinement Fusion experiments or plasma photonics applications of gratings in high-field laser-physics and high-energy density science, specifically in the nanosecond regime.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1638009
• Report Number(s): LLNL--JRNL-763069; 950368
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 7 Vol. 26; ISSN 1070-664X; ISSN 1089-7674
• Publisher: American Institute of Physics (AIP)Copyright Statement
• Country of Publication: United States
• Language: English