Three-dimensional filamentation of light in laser plasmas

Journal Article · Mon Dec 31 23:00:00 EST 1990 · Physics of Fluids B; (USA)

DOI:https://doi.org/10.1063/1.859936· OSTI ID:6389958

Schmitt, A J ^[1]

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1. Laser Plasma Branch, Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (US)

The first calculations of time-dependent laser--plasma filamentation in three dimensions are reported. These calculations are done with a three-dimensional laser propagation code based on a previous two-dimensional code (Phys. Fluids {bold 31}, 3079 (1988)). The effect of incident beam structure, and in particular optical smoothing techniques, on the behavior of filamentation is studied. Both ponderomotive and thermal conduction dominated nonlinearities are considered, and calculations are done simulating both homogeneous nonabsorbing plasmas and inhomogeneous laboratory plasmas. Random phase screen (RPS) and induced spatial incoherence (ISI) optical smoothing techniques are investigated and compared to generic unsmoothed laser beams. Qualitative examples are presented and scaling studies are done and compared to a simple theoretical analysis. In typical laser--plasma interactions without optical smoothing, three-dimensional effects lead to greatly increased filament intensities, as expected. Peak filament intensities of order 100--500 times the average intensity are routinely observed (without optical smoothing), as compared to earlier two-dimensional calculations where peak intensities were of order 10--50 times average. In spite of this tendency to create stronger filaments, three-dimensional filamentation (when measured on a time-averaged basis) can be suppressed by using ISI smoothing. Under the same conditions, instantaneous ISI intensities can show considerable enhancement, although much less than the unsmoothed beams. RPS smoothing exhibits less filamentation suppression. Under laser-fusion reactor conditions, calculations indicate that ISI suppression can completely eliminate filamentation.

• OSTI ID: 6389958
• Journal Information: Physics of Fluids B; (USA), Journal Name: Physics of Fluids B; (USA) Vol. 3:1; ISSN 0899-8221; ISSN PFBPE
• Country of Publication: United States
• Language: English

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BEAM-PLASMA SYSTEMS
DIFFERENTIAL EQUATIONS
ELECTRIC POTENTIAL
ELECTROMAGNETIC FIELDS
ENERGY TRANSFER
EQUATIONS
HEAT TRANSFER
HOMOGENEOUS PLASMA
INHOMOGENEOUS PLASMA
INSTABILITY
LASER-PRODUCED PLASMA
MAXWELL EQUATIONS
NONLINEAR PROBLEMS
OPTICS
PARTIAL DIFFERENTIAL EQUATIONS
PLASMA
SCALING LAWS
SWELLING
THERMAL CONDUCTION
THREE-DIMENSIONAL CALCULATIONS
TIME DEPENDENCE
WAVE EQUATIONS
WAVE PROPAGATION