Pulse Compression in Plasma-Gratings Generated on Density Gradient

Chirped-pulse amplification (CPA) is approaching its technological limit at petawatts, due to damage to solid-state compression gratings. To reach exawatt and even zettawatt regimes—crucial for probing phenomena like pair production and the Schwinger limit—new compression techniques are needed. Plasma-based pulse compression emerges as a strong candidate because plasma is already ionized and free from damage while also being highly dispersive. Techniques such as Raman and Brillouin amplification use dynamic plasma gratings, while more recent work uses static plasma structures to achieve compression factors of 10–100. In our recently proposed scheme [1], a high-density plasma with a density gradient is used to compress negatively chirped pulses via frequency-dependent reflection. However, generating large plasma mirrors is technically difficult, and even slight density fluctuations can severely deteriorate compression. To overcome these issues, we propose a gradient plasma photonic crystal (GPPC) structure, which lowers the required plasma density and enhances robustness to fluctuations. Adjusting the base density, modulation depth, and grating period allows the cutoff frequency of the 1^st bandgap to shift in ways that enable compensation for local density variations. Particle-in-cell (PIC) simulations confirm that GPPC structures can successfully compress pulses even in the presence of significant density fluctuations.

[1] Hur et al., Nat. Phot. 17, 1074 (2023).