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Dynamics of Raman instabilities using chirped laser pulses
J Faure1, J R Marquès, V Malka
1Laboratoire pour l'Utilisation des Lasers Intenses, UMR 7605, CNRS-CEA-Ecole Polytechnique-Université Pierre et Marie Curie, 91128 Palaiseau Cedex, France.
Summary
Short laser pulses (<10 ps) drive Raman instabilities at the pulse's back. Instability growth is chirp-sign independent, matching a temporal model that shows plasma wave damping for longer pulses.
Area of Science:
- Plasma Physics
- Laser-Plasma Interactions
- Nonlinear Optics
Background:
- Raman instabilities are crucial in laser-plasma interactions, affecting energy transfer and particle acceleration.
- Understanding the temporal dynamics of these instabilities is key to controlling them.
- Previous studies often focused on longer pulses or lacked time-resolved measurements.
Purpose of the Study:
- To experimentally investigate the time-resolved growth of Raman instabilities using picosecond chirped laser pulses.
- To develop and validate a temporal model for these instabilities.
- To determine the influence of laser pulse chirp on instability growth and plasma wave damping.
Main Methods:
- Time-resolved measurements of Raman scattering using a picosecond chirped laser pulse.
- Experimental observation of forward and 30-degree Raman scattering.
- Development of a simple temporal model to simulate instability growth.
Main Results:
- Forward and 30-degree Raman scattering were observed at the back of short laser pulses (<10 ps).
- Instability growth was independent of the sign of the laser pulse chirp.
- The developed temporal model showed good agreement with experimental data.
Conclusions:
- Short laser pulses (<10 ps) can drive Raman instabilities at the rear of the pulse.
- The plasma wave driven by forward Raman scattering is significantly damped for pulses longer than a few picoseconds.
- Modulational instability is a plausible mechanism for damping, consistent with experimental findings.