Study of Direct Amplification of Ultrashort Light Pulses in a Laser Amplifier with a View to Obtaining High Radiation Contrast

An amplification scheme for ultrashort laser pulses of high radiation contrast was used to perform experiments on ablation pressure symmetrization using a prepulse upon acceleration of thin foils. It is shown that the spontaneous radiation of the regenerative amplifier restricts the energy contrast in the amplification of chirped pulses at a level of 10^-4–10^-3. The possibility of direct amplification of a short pulse with a view to increasing the energy contrast ratio was considered. Experiments were performed on the PICO laser facility to demonstrate that a 10-ps pulse amplification achieved an intensity 100 GW/cm², a gain factor of 1.2, and an inversion dumping factor >30%.