High intensity regimes for resonant Raman compression

In order to achieve the largest laser intensities, a plasma might be used as the amplification medium, thereby avoiding the material limits of conventional materials. The technique considered is resonant backward Raman amplification in plasma, wherein a short counter-propagating seed pulse, with frequency downshifted from a long pump pulse by the plasma frequency, absorbs the pump energy through a resonant decay interaction of the two counter-propagating light waves and a plasma wave. In the pump-depletion regime, the counter-propagating seed pulse assumes a self-contracting self-similar form, capturing the pump energy in a pulse of far shorter duration. This technique encounters limitations both at high laser seed output intensities and high pump laser intensities. At high seed output intensities, there are modulation instabilities that break up the output seed. At high pump intensities, the resonant interaction is interrupted by wavebreaking of the plasma wave. These limitations, while limiting, may not be as limiting as might be at first thought.