Propagation of realistic beams in underdense plasma

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Abstract
The effect of beam structure on propagation through underdense plasma is examined in two different examples. First, it is shown that the distribution of intensities within a laser beam affects how the beam deflects in the presence of transverse plasma flow. A detailed analysis of beam deflection shows that the rate scales linearly with intensity and plasma density, and inversely with plasma temperature. When the plasma flow is subsonic, the deflection rate is proportional to the ion damping decrement, and scales as M/(1−M2)3/2, where M is the transverse flow Mach number. When the plasma flow is supersonic, the deflection rate scales as 1/[M(M2−1))1/2]. Next, the effect of beam structure on channel formation by very intense laser beams is studied. A diffraction-limited beam with ∼3 TW of input power forms a channel through 400 μm of plasma, whereas when this beam is phase aberrated, channel formation does not occur.