Stable pulse compression in a gradient-plasma photonic crystal

Plasma-based schemes for high-power laser compression has been considered promising as future alternatives of conventional CPA (chirped-pulse-amplification) techniques, where the damage-sensitive compression gratings give the upper limitation of the laser power up to a few petawatts. As the simple extrapolation of the current scheme of CPA to exawatt or zettawatt implies that the diameter of gratings be made hundreds of meters, which is challenging, a fundamentally different approach is required. Recently we have demonstrated by simulations that a strong pulse compression by hundreds of times can be achieved using a smooth density gradient of near-critical plasma (Hur et al., Nat. Phot. 2023). The underlying idea is, producing reflection path differences of photons with different frequencies in a chirped, long laser pulse. This idea, however, requires a milli-meter-long plasma with critical density and smooth-enough profile, which can be extremely challenging. Even a small deviation of the density from the pre-designed profile can lead to spread of reflected photons from their compressed position, deteriorating the compression efficiency considerably. In this presentation, we theor