Simulations of efficient Raman amplification into the multipetawatt regime

Contemporary high-power laser systems make use of solid-state laser technology to reach petawatt pulse powers. The breakdown threshold for optical components in these systems, however, demands metre-scale beams. Raman amplification of laser beams promises a breakthrough by the use of much smaller amplifying media, that is, millimetre-diameter plasmas, but so far only 60 GW peak powers have been obtained in the laboratory, far short of the desired multipetawatt regime. Here we show, through the first large-scale multidimensional particle-in-cell simulations of this process, that multipetawatt peak powers can be reached, but only in a narrow parameter window dictated by the growth of plasma instabilities. Raman amplification promises reduced cost and complexity of intense lasers, enabling much greater access to higher-intensity regimes for scientific and industrial applications. Furthermore, we show that this process scales to short wavelengths, enabling compression of X-ray free-electron laser pulses to attosecond duration.