Fig. 1. Illustration of laser compression by a fast-extending plasma grating (FEPG) produced with a short ionizing pulse (brown pulse, cross-polarized) and a phonon (transparent green fringes) in a background gas. As the boundary of the plasma grating (green fringes) moves with the ionizing pulse, the reflected pulse (blue pulse) of the pump (red pulse) is compressed.

Fig. 2. One-dimensional PIC simulation results for pulse compression by FEPG at ρ₀ = 0.01n_c, ρ/ρ₀ = 0.5, a₀ = 0.002, Λ = 0.502 35λ_a, and λ_a = 1 µm, corresponding to T = 3.3 fs. (a) Pump (red) and RP (blue) at t = 150T. (b) Evolution of RP profiles at different interaction times. (c) Overall and (d) specific distributions of plasma grating and background gas at t = 2000T. (e) Logarithmic spatial frequency intensity of electron density. (f) Electron temperature at t = 2000T. (g) Normalized spectra of RP at t = 100T and 2000T. (h) Normalized spectrum of 10T 1 µm laser pulse at t = 2000T used to ionize a uniform background gas of density 0.02n_c.

Fig. 3. One-dimensional simulation results for (a) amplitude magnification and (b) compression ratio from FEPGC with various pump amplitudes. (c) Two-dimensional simulation result with ρ₀ = 0.01n_c and a₀ = 0.006.

Fig. 4. One-dimensional PIC simulation result for FEPGC for various ρ and ρ₀. (a) Profile of pump intensity at t = 2000T with ρ/ρ₀ = 0.5, ρ₀ = 0.01n_c, and a₀ = 0.006. (b) Pump penetration depth for various ρ/ρ₀ and ρ₀. (c) AM for different ρ with ρ₀ = 0.01n_c, a₀ = 0.006, and Λ = 0.502 35λ_a. (d) AM for different gas densities ρ₀ with ρ/ρ₀ = 0.5, a₀ = 0.006, and Λ adjusted according to the maximum AM.

Fig. 5. One-dimensional PIC simulation results for inhomogeneous plasmas. (a) Density profiles and (b) spatial frequency intensities of plasma gratings with random or periodic density fluctuations. (c) AM and (d) RP spectra for inhomogeneous plasmas.

Fig. 6. One-dimensional numerical simulation and analytical calculation of the phonon generated by two 3 ns counterpropagating laser pulses in 1 atm 20 °C hydrogen. (a) Simulation results for the laser intensity distribution after 3 ns. (b) Simulation results for ρ/ρ₀ at different times. (c) Evolution of ρ/ρ₀ obtained from the analytical solution.

Table 1. Steady-state values of ρ/ρ₀ for several gases. Both laser pulses have wavelength 1 µm, the gas pressure P = 1 atm, and the temperature T = 20 °C. The laser intensity I is expressed in units of 10¹² W/cm².