Measurements of forward scattered laser radiation from intense sub-ps laser interactions with underdense plasmas

摘要

Two experiments studying the interaction of high intensity laser pulses (1x10(19)-5x10(20) W/cm(2)) with underdense plasma are compared. The experiments used lasers that differed in power and focused intensity but had similar pulse duration (similar to 1 ps). Spectroscopic measurements of the forward scattered light (sidebands) near the fundamental laser frequency produced by the self-modulation instability were performed and the energies of electrons accelerated in the interaction are measured and compared. It is found that at high intensities the sideband intensities and the electron energies were not directly correlated, implying that relativistic plasma wave generation is not the most important mechanism for electron acceleration in the ultrahigh intensity regime. Simulation results for the forward scattered spectrum agree well with experimental results. (c) 2006 American Institute of Physics.