Relativistic Engineering and Extreme Field Science

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We have carried out the first ever experiment that shows the efficacy of "Relativistic Engineering".We have experimentally demonstrated the reflection of a laser pulse from the wake generated by another ultrashort, high-irradiance laser pulse propagating in underdense plasma. The reflection is accompanied by the relativistic frequency upshifting by a factor ranging from 55 to 114, with the reflected pulse in the XUV spectral region (the wavelength is from 7 to 15 nm). In several shots, the signal exceeds noise by five standard deviations. Our interpretation is corroborated by correlations of the reflected signal with the source pulse delay and spatial alignment, small size of the reflected signal origin, and dependence of the signal presence on the crossing-point position. In addition, the results are in a good agreement with the 2D PIC simulations, including the frequency multiplication factor, the reflected pulse bandwidth, and the position of the goodquality wake wave. The PIC simul … More ation gives also the angular distribution of the reflected signal consistent with the focusing paraboloidal shape of the reflecting surfaces.Our proof-of-principle experiments open a way to generate coherent ultrashort pulses in the VUV, XUV, soft x-ray, and x-ray spectral regions using the reflection from the relativistic flying mirror. The reflected pulses are orders of magnitude shorter than the original laser pulses employed. The reflected pulses are also conceived to be focusable to record intensities due to the smaller focal spot size. The setup fits into the size of a laboratory-scale experiment. The flying mirror technique is scalable, which eventually may lead to intensities under which the nonlinearities of vacuum can be detected. Apart from this, the radiation reflected from the wake wave can provide important information about the wake phase velocity, length, density modulations, etc.In addition, we demonstrate the generation of the polarized Thomson backscattered x-rays in the 400 keV energy region by using the Nd : YAG laser and the 150 MeV electron beam from the microtron accelerator. The source of the tunably polarized x-rays in this energy region is unique at the present. Less