Dependence of relativistic self-guiding and Raman forward scattering on duration and chirp of an intense laser pulse propagating in a plasma

Relativistic self-guiding and Raman forward scattering of an intense ultrashort laser pulse propagating in an underdense plasma were studied using a terawatt Ti:sapphire laser system. The dependence of these processes on the duration and frequency chirp of the laser pulse was investigated by detuning the pulse compressor. It was observed that the efficiency of Raman forward scattering is enhanced for a positively chirped pulse and diminished for a negatively chirped pulse. In addition, as a result of the dependence on pulse duration and peak power, an optimal duration for Raman forward scattering was found for fixed pulse energy and spectral bandwidth. On the other hand, relativistic self-guiding of the laser pulse was affected by the pulse duration while no dependence on the chirp was observed.