Contrast enhancement of ultra-intense laser pulses by relativistic plasma shutter

An increasing intensity of the laser systems becomes available for experiments in the fields of particle acceleration, radiation sources and many other applications. The higher intensity of the laser irradiation is inherently accompanied by the growth of the amplified spontaneous emission (ASE) pedestal and other parasitic effects. Considering the forthcoming generation of multi-PW laser systems, the nanosecond and picosecond pedestals significantly exceed the respective plasma formation thresholds and may have detrimental effects on the laser--target interaction. One of the promising methods to mitigate these effects is the relativistic plasma shutter, where an ultra-thin foil is placed in front of the target. The initial interaction with the shutter increases the temporal contrast, where the pre-plasma is opaque for the pedestal, but relativistically transparent for the main pulse. Moreover, the created pre-plasma exhibits a focussing effect, increasing the effective intensity of the main pulse. Two-dimensional hydrodynamic simulations of the pedestal are performed, followed by PIC simulations of the main pulse. The parameters of the shutter, like density and thickness, are varied to optimize performance of the configuration.