Propagation of Short Laser Pulses in Plasma Channels.
NAVAL RESEARCH LAB WASHINGTON DC
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Finite pulse length effects are shown to play a major role in the propagation, stability and guiding of intense laser beams in plasmas. We present the quasi paraxial approximation QPA to the wave equation that takes finite pulse length effects into account. The QPA is an extension of the usual paraxial approximation. The laser field is shown to be significantly modified for pulses less than a few tens of wavelengths long. A pair of coupled envelope-power equations having finite pulse length effects, as well as relativistic and atomic electron nonlinearities, is derived and analyzed. Short laser pulses propagating in plasma channels are found to undergo an envelope oscillation in which the front of the pulse is always damped while the back initially grows. The modulation eventually damps due to frequency spread phase mixing. In addition, finite pulse length effects are shown to significantly modify nonlinear focusing processes.
- Lasers and Masers
- Nuclear Physics and Elementary Particle Physics