Laser pulse compression by a density gradient plasma for exawatt to zettawatt lasers

Abstract We propose a new method of compressing laser pulses to ultra-high powers based on spatially varying dispersion of a plasma plume that has a density gradient. Here, compression is achieved when a long, negatively frequency-chirped laser pulse reflects off the density ramp of an over-dense plasma slab. As the density increases longitudinally, high frequency photons at the leading part of the laser pulse penetrate more deeply into the plasma region than lower frequency photons, leading to pulse compression in a similar way to that off a chirped mirror. Proof-of-principle simulations carried out using a one-dimensional (1-D) particle-in-cell (PIC) simulation code demonstrate compression of 2.35 ps laser pulse to 10.3 fs, with a compression ratio of 225. As plasma is robust and resistant to damage at high intensities, unlike solid-state gratings commonly used in chirped-pulse amplification (CPA), the method could be used as a compressor to reach exawatt or zettawatt peak powers.