Fast decompression of ultra-thin targets for high-energy, high-contrast laser pulses

In the laser-plasma interaction process, for ultra-high temporal contrast laser pulses, experimental measurements show that reducing the thickness of solid targets increases the laser-to-fast electrons energy conversion and the hot electron temperature. We have performed an experiment using the LULI 100 TW laser facility working in the chirped pulse amplification (CPA) mode at a wavelength λ₀=1.057 μm, pulse duration 320 fs, laser spot size FWHM ∼6 μm and intensity ∼1×10¹⁸ W/cm ² in which the laser pulses were temporal-contrast enhanced by the use of two plasma mirrors. Shots were performed on Si₃N₄ aluminum coated targets of thickness 30 nm to 500 nm. Spectra of the laser-accelerated electrons were recorded with a spectrometer and are compared to PIC simulations performed with the CALDER code. The simulations allow an insight into the electron heating process during the laser-matter interaction.